Chapter 21 Anatomy and Physiology

HOMEOSTASIS FIGURE 21.43 Summary of the Effects of pH and Gases on Blood Pressure.

(1) Blood pH is within its normal range. (2) Blood pH increases outside the normal range, w which causes homeostasis to be disturbed. (3) Chemoreceptors detect the increase in blood pH. The cardioregulatory and vasomotor centers in the brain are inhibited. (4) Nervous and hormonal changes alter the activity of cardiac muscle of the heart rate and smooth muscle of the blood vessels (effectors), causing heart rate and stroke volume to decrease and blood vessels to dilate, reducing blood flow to the lungs, which increases blood CO2. (5) These changes cause blood pH to decrease. (6) Blood pH returns to its normal range, and homeostasis is restored. Observe the responses to a decreases in blood pH outside its normal range by following the red arrows. For more information on the chemoreceptor reflex, see figure 21.42; for the central nervous system ischemic response, see the text.

FIGURE 21.5 Structure of Capillary Walls

(c) Sinusoidal capillaries have large fenestra without diaphragms and can have gaps between endothelial cells. They are found in endocrine glands, bone marrow, the lier, the spleen, and the lymphatic organs.

FIGURE 21.15 Branches of the Aorta

(c) The abdominal aorta.

What do the subclavian veins form?

On each side of the body the internal jugular veins merge with the subclavian veins to form the brachiocephalic veins.

Where can the pulse be felt on the head and neck/

On the head and neck, a pulse can be felt in three arteries (1) the common carotid artery in the neck, (2) the superficial temporal artery immediately anterior to the ear, and (3) the facial artery at the point where it crosses the inferior border to the mandible approximately midway between the angel and the genuflects.

Once the internal jugular veins exit the cranial cavity what do they receive?

Once the internal jugular veins exit the cranial cavity, they receive several venous tributaries that drain the external head and face.

What happens once the internal jugular veins exit the cranial cavity?

Once the internal jugular veins exit the cranial cavity, they receive several venous tributaries that drain the external head and face. -On each side of the body the internal jugular veins merge with the subclavian veins to form the brachiocephalic veins.

Veins Brachiocephalic Facial

Superficial and anterior facial structures

Veins: Brachiocephalic Facial

Superficial and anterior facial structures

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Great saphenous

Superficial anterior and medial leg, thigh, and dorsal of foot

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Small saphenous

Superficial posterior leg and lateral side of foot

Veins: Brachiocephalic External jugular

Superficial surface of posterior head and neck

Veins: Internal Jugular Vein Superior sagittal sinus

Superior portion of cranial cavity and brain

Arteries: Parietal Branches Superior phrenic

Superior surface of diaphragm.

What are systemic vessels?

Systemic vessels transport blood from the left ventricle, through all parts of the body, and back to the right atrium.

Vessels Systemic Heart

TOTAL BLOOD VOLUME 7/100

Vessels Systemic Capillaires

TOTAL IN SYSTEMIC VESSELS 5/84

Arteries: Common Carotid Arteries External Carotid Superficial temporal

Temple, face, and anterior ear

Veins: Gonadal Testicular (male)

Testis

Veins: Inferior Vena Cava Gonadal Testicular (male)

Testis

Paried: Gonadal Testicular (male)

Testis and ureter

What is the abdominal aorta?

The abdominal aorta is the part of the descending aorta that extends from the diaphragm to the point at which the aorta divides into the two common iliac arteries. -The abdominal aorta has several branches that supply the abdominal wall and organs. -Its terminal branches, the common iliac arteries, supply blood to the pelvis and lower limbs.

How is the amount of blood flow through a blood vessel regulated?

The amount of blood flowing through a blood vessel can be regulated by contraction or relaxation of the smooth muscle in the tunica media.

Describe the anterior and posterior tibial veins.

The anterior and posterior tibial veins are paired and accompany the anterior and posterior tibial arteries. -They unite just inferior to the knee to form the single popliteal vein, which ascends through the thigh and becomes the femoral vein.

What does the anterior tibial artery become?

The anterior tibial artery becomes the dorsals pedis artery at the foot.

What is the left aortic arch.

The aorta then arches posteriorly and to the left as the aortic arch.

What do the arteries of the lower limb form?

The arteries of the lower limb form a continuum similar to that of the arteries of the upper limb.

FIGURE 21.3 Arteries of the Upper Limb

The arteries of the right upper limb and their branches; the right brachiocephalic, subclavian, axillary radial, and ulnar arteries and their branches.

PROCESS FIGURE 21.32 Blood Pressure Measurement

The auscultatory method, illustrated in this figure, allows medical professionals to measure arterial blood pressure.

Where is the axillary artery located?

The axillary artery is the continuation of the subclavian artery in the axilla.

What becomes the axillary vein?

The basilic vein of the arm becomes the axillary vein as it passess through the axillary region.

What becomes the axillary vein?

The basilica vein of the arm becomes the axillary vein as it passes through the axillary region.

What is the brachial artery?

The brachial artery is the continuation of the axillary artery as it passes into the arm.

What does the external iliac artery become?

The external iliac artery becomes the femoral artery in the thigh, which become the popliteal artery in the popliteal space.

What does the femoral vein become?

The femoral vein becomes the external iliac vein.

What are three major veins that return blood from the thorax?

Three major veins return blood rom he thorax to the superior vena cava: (1) the right brachiocephalic vein, (2) the left brachiocephalic vein, and (3) the azygos vein.

Arteries: Common Carotid Arteries External Carotid Ascending pharygneal

Deep neck muscles, middle ear, pharynx, soft palate, and meninges around posterior brain

Veins: Internal Jugular vein Straight sinus Inferior sagittal sinus

Deep portion of longitudinal fissure

Veins: Internal Jugular Vein: Inferior sagittal sinus

Deep portion of longtiudinal fissure.

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Posterior tibial

Deep posterior leg

Veins: Axillary (continuation of the basilica vein) Brachial (paired, deep veins)

Deep structures of the arm

Veins: Axillary (continuation of the axillary vein) Brachial (paired deep veins)

Deep structures of the arm.

FIGURE 21.34 Major Points at Which the Pulse Can Be Monitored

Each pulse point is named after the artery on which it occurs.

Vessels Systemic Pulmonary vessels

9

Stage 2 hypertension

=>140/=>90

Veins: Axillary (continuation of the basilic vein) Radial

Deep forearm

Veins: Axillary (continuation of the basilica vein) Radial

Deep forearm

Veins: Axillary (continuation of the basilica vein) Ulnar

Deep forearm

HOMEOSTASIS FIGURE 21.40 Summary of the Baroreceptor Effects of Blood Pressure

(1) Blood pressure is within its normal range. (2) Blood pressure increases outside the normal range, which causes homeostasis to be disturbed. (3) Baroreceptors detect the increase in blood pressure. The cardioergulatory and vasomotor centers int eh brain respond to changes in blood pressure. (4) Nervous and hormonal changes alter the activity of cardiac muscle of the heart and smooth muscle of the blood vessels (effectors), causing heart rate and stroke volume to decrease blood vessels to dilate. (5) These changes cause blood pressure to decreases. (6) Blood pressure returns to its normal range, and homeostasis is restored. Observe the responses to a decreases in blood pressure outside its normal range by following the red arrows. For more information on the baroreceptor reflex, see figure 21.39; for the adrenal medullary mechanism, see figure 21.41.

HOMEOSTASIS FIGURE 21.46 Summary of Long-Term (Slow-Acting ) Blood Pressure Control Mechanisms.

(1) Blood pressure is within its normal range. (2) Blood pressure increases outside the normal range, which causes homeostasis to be disturbed. (3) Increased blood pressure is detected by cardiac muscle cells and the kidney (receptors0. The hear and kidneys (control center) respond to increased blood pressure by secretion of hormones. (4) Blood vessels of the body and the kidneys (effectors) respond to the hormones by dilating or adjusting blood volume through urine formation. (5) These changes cause blood pressure to decrease. (6) Blood pressure returns to its normal range, and homeostasis is restored. Observed the responses to a decrease in blood pressure outside its normal range by following the red arrows. For more information on the renin-angiotensin-aldosterone mechanism, see figure 21.44; for the antidiuretic hormone mechanism, see figure 21.45; for the atrial natiuretic mechanism, see figure 27.6

Vessels Systemic Small veins

(25%)

Vessels Systemic Veins Large veins

(39%)

FIGURE 21.33 Blood Vessel Area and Velocity of Blood Flow

(a) A schematic representing the total cross-sectional area for each of the major blood vessel types. The total cross-sectional area of all the capillaries is much greater (2500 cm^2) than that of the aorta (5 cm^2), although the cross-sectional area of each capillary is much smaller than that of the aorta. (b) Blood velocity decreases dramatically in arterioles, capillaries, and venules and is greater in the aorta and the large veins. As the total cross-sectional area increases, the velocity of blood flow decreases.

FIGURE 21.5 Structure of Capillary Walls

(a) Continuous capillaries have no gaps between endothelial cells and no fenestra. They are common in muscle, nervous, and connective tissue.

FIGURE 21.31 Laminar and Turbulent Flow

(a) In laminar flow, fluid flows in long, smooth-walled tubes as if it were composed of a large number of concentric layers.

FIGURE 21.15 Branches of the Aorta

(a) The aorta is considered in three portions: the ascending aorta, the aortic arch, and the descending aorta. The descending aorta and the abdominal aorta.

FIGURE 21.5 Structure of Capillary Walls

(b) Fenestrated capillaries have fenestra 7-100 nm in diameter, covered by thin, porous diaphragms, which are not present in some capillaries, which are not present in some capillaries. They are found in intestinal villi, ciliary processes of the eyes, choroid plexuses of the central nervous system, and glomeruli of the kidneys.

FIGURE 21.15 Branches of the Aorta

(b) The thoracic aorta

FIGURE 21.31 Laminar and Turbulent Flow

(b) Turbulent flow is caused by numerous small currents flowing crosswise or obliquely to the long axis fo the vessel, resulting in flowing whorls and eddy currents.

What do the middle cerebral arteries connect to?

-The middle cerebral arteries connect to the posterior cerebral arteries by way of the posterior communicating arteries. -These connections complete a circule around the pituitary gland and the base of the brain called the cerebral arterial circle.

What exist in venules?

-A few isolated smooth muscle cells exist outside the endothelial cells, especially in the larger venules. -As the vessels increase to 0.2-0.3 mm in diameter, the smooth muscle cells form ac ontinous layer; the vessels are then called small veins. -In addition to a larger diameter compared to venules, small veins also have a tunica adventitia composed of collagenous connective tissue.

Describe baroreceptors in the blood vessels.

-A few myelinated sensory neurons innervate some blood vessels and function as baroreceptors. -They monitor stretch in the blood vessel wall and detect changes in blood pressure.

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Fibular (peroneal)

Deep lateral leg and foot

What is ANH?

-A polypeptide called atrial natriuretic hormone (ANH) is released from cells in the atria of the heart. -A major stimulus for its release is increased venous return, which stretches atrial cardiac muscle cells. -Atrial natriuretic hormone acts on the kidneys to increase the rate of urine production and Na+ loss in the urine. -It also dilates arteries and veins. -Loss of water and Na+ in the urine causes the blood volume to decrease, which decreases venous return, and vasodilation results in a decrease in peripheral resistance. -These effects cause a decrease in blood pressure.

What is a stress-relaxation response?

-A stress-relaxation response is characteristic of smooth muscle cells. -When blood volume suddenly declines, blood pressure also decreases, reducing the force applied to smooth muscle cells in blood vessel walls. -As a result, during the next few minutes to an hour, the smooth muscle cells contract, reducing the volume of the blood vessels, and thus resisting a further decline in blood pressure. -Conversely, when blood volume increases rapidly, as occurs during a transfusion, blood pressure increases, and smooth muscle cells of the blood vessel walls relax, resulting in a more gradual increase in blood pressure. -The stress-relaxation mechanism is most effective when changes in blood pressure occur over a period of many minutes.

What is a stroke?

-A stroke is a sudden neurological disorder, often caused by decreased blood supply to a part of the brain. -It can occur as a result of a thrombosis, an embolism, or a hemorrhage. -Any one of these conditions can reduce the brain's blood supply or cause trauma to a part of the brain. -As a result, the tissue normally supplied by the arteries become necrotic, forming an infarct in the affected area(s).

What does ADH act directly on?

-ADH acts directly on blood vessels to cause vasoconstriction, although it is not as potent as other vasoconstrictors. -Within minutes after a rapid and substantial decline in blood pressure, ADH is released in sufficient quantities to help reestablish normal blood pressure. -ADH also decreases the rate of urine production by the kidneys, thereby helping maintain blood volume and blood pressure.

What conditions result in hypertension?

-Although many known conditions result in hypertension, roughly 90% of the diagnosed cases are called idiopathic hypertension, or essential hypertension, which means that the cause of the conditions is unknown. -Drugs that dilate blood vessels (called vasodilators), drugs that increase the rate of urine production (called diuretics), and drugs that decrease cardiac output are normally used to treat idiopathic hypertension. -The vasodilator drugs increase the rate of blood flow through the kidneys and thus increase urine production; the diuretics increase urine production as well. -Increased urine production reduces blood volume, which reduces blood pressure. -Substances that decrease cardiac output, such as B-adrenergic blocking agents, decrease the heart rate and force of contraction. -In addition to these treatments, low-salt diets are normally recommended to reduce the amount of sodium chloride (NaCl) and water absorbed from the intestine into the bloodstream.

What is a good analogy of compliance?

-An analogy to clarify this relationship is comparing the volume of water a plastic cup can hold with the volume of water a water ballon can hold. -The water ballon has the capacity to stretch, or has a greater compliance, compared to a plastic cup.

What does angiotensin II cause?

-Angiotensin II causes vasoconstriction in arterioles and, to some degree, in veins. -As a result, it increases peripheral resistance and venous return to the heart, both of which raise blood pressure. -Angiotensin II also stimulates aldosterone secretion from the adrenal cortex. -Aldosterone acts on the kidneys to increase the reabsorption of Na+ and Cl- from the filtrate into the extracellular fluid. -If antidiuretic hormone is present, water moves by osmosis with the Na+ and Cl-. -Consequently, aldosterone causes the kidneys to retain solutes, such as Na+ and Cl-, and water. -The result is increased blood volume by decreasing the production of urine and conserving water. -Angiotensin II also increases salt appetite, thirst, and ADH secretion.

What can stimulate aldosterone secretion?

-Angiotensin II is not the only stimulus for aldosterone secretion. -Other stimuli can directly stimulate aldosterone secretion. -For example, an increased plasm ion concentration of K+ and a reduced plasma concentration of Na+ directly stimulate aldosterone secretion from the adrenal cortex. -Aldosterone regulates the concentration of these ions in the plasma. -A decreased blood pressure and an elevated K+ concentration occur during plasma loss, during dehydration, and in response to tissue damage, such as burns and crushing injuries.

What are Angiotensin-converting enzymes?

-Angiotensin-converting enzyme (ACE) inhibitors are a class of drugs that inhibit angiotensin-converting enzyme, which converts angiotensin I to angiotensin II. -These drugs were first identified as components of venom of pit vipers. -Subsequently, several ACE inhibitors were synthesized. -ACE inhibitors are commonly administered to combat hypertension.

What is capillary exchange?

-Approximately 10 billion capillaries exist in the body. -The heart and blood vessels maintain blood flow through those capillaries and support capillary exchange, which is the movement of substances into and out of capillaries. -Capillary exchange is the process by which cells receive everything they need to survive and to eliminate metabolic waste products. -If blood flow through capillaries is not maintained, cells cannot survive.

Describe how autoregulation.

-Arterila pressure can change over a wide range, whereas blood flow through tissues remains relatively constant. -The maintenance of blood flow by tissues is called auto regulation. -Between arterial pressures of approximately 75 mm Hg and 175 mm Hg, blood flow through tissues remains within 10-15% of its normal value. -The mechanisms responsible for auto regulation are the same as those for vasomotion. -The need for O2 and nutrients and the buildup of metabolic by-products cause precapillary sphincters to dilate, and blood flow through tissues increases if a minimum blood pressure exists. -On the other hand, once the supply of O2 and nutrients to tissues is adequate, the precapillary sphincters constrict, and blood flow through the tissues decreases, even if blood pressure is very high.

What are arterioles?

-Arterioles are the smallest arteries in which the three layers can be identified. -They transport blood from small arteries to capillaries. -They range in diameter from approximately 40 micrometers, which is less than half the thickness of a sheet of printer paper, to as small as 9 micrometer.

Arteries: Abdominal Aorta Visceral Branches Upaired Common hepatic Gastroduodenal

Stomach and duodenum

What is arteriosclerosis?

-Arteriosclerosis consist of degenerative changes in arteries that make them less elastic. -These changes occur in many individuals, and they become more sever with advancing age. -Arteriosclerosis greatly increases resistance to blood flow. -Therefore, advanced arteriosclerosis reduces the normal circulation of blood and greatly increases the work performed by the heart.

What is a pulse?

-As blood is ejected from the left ventricle into the aorta, it produces a pressure wave, or pulse, that travels rapidly along the arteries. -Its rate of transmission is approximately 15 time greater in the aorta (7-10 m/s) and 100 times greater in the distal arteries (15-35m/s) than the velocity of blood flow.

What is blood pressure influenced by?

-As indicated by equation (21.9), blood pressure is influenced by three factors: (1) heart rate, (2) stroke volume, and (3) peripheral resistance. -An increase in any one of these elevates blood pressure. -Conversely, a decrease in any one of them reduces blood pressure. -Because stroke volume depends on the amount of blood entering the heart, regulatory mechanisms that control blood volume also affect blood pressure. -For example, an increase in blood volume increases venous return, which increases preload, and the increased preload increases stroke volume.

What happens to the pulse as it passes through the smallest arteries and arterioles?

-As the pulse passes through the smallest arteries and arterioles, it is gradually damped, so that the fluctuation between the systolic and diastolic pressures becomes smaller until the difference is almost absent at the end of the arterioles. -At the beginning of the capillary, there is a steady pressure of close to 30 mm Hg, which is adequate to force blood through the capillaries if the precapillary sphincters dilate.

What happens as the rate of metabolism increases?

-As the rate of metabolism increases in a tissue, vasodilator substances are produced in the extracellular fluid. -These substances include CO2, lactate, adenosine, adenosine monophosphate, adenosine diphosphate, endothelium-derived relaxation factor (EDRF), K+, and H+. -Once produced, the vasodilator substances diffuse from the tissues supplied by the capillary to the area of the precapillary sphincter, the metarterioles, and the arterioles to cause vasodilation and relaxation of the precapillary sphincters.

What can prevent atherosclerosis?

-Avodiing the environmental factors that influence atherosclerosis slows the development of atherosclerotic plaques. -In some cases, the severity of the plaques can be reduced by behavioral modifications and/or drug therapy. -For example, regulating blood glucose levels in people with diabetes mellitus and taking drugs that lower high blood cholesterol can provide some protection.

What are baroreceptors?

-Baroreceptor reflexes are very important in regulating blood pressure on a minute-to-minute basis. -They detect even small changes in blood pressure and respond quickly. -However, they are not as important as other mechanisms in regulating blood pressure over long periods of time. -Baroreceptors, or pressoreceptors, are sensory receptors sensitive to stretch. -They are scattered along the walls of most of the large arteries of the neck and thorax and are most numerous in the area of the carotid sinus at the base of the internal carotid artery and in the walls of most large aortic arch. -Action potentials travel from the carotid sinus baroreceptors through the glossopharyngeal (IX) nerves to the cardioregulatory and vasomotor centers in the medulla oblongata and from the aortic arch through the vagus (X) nerves to the medulla oblongata. -Stimulation of baroreceptors in the carotid sinus activates the carotid sinus reflex, and stimulation of baroreceptors in the aortic arch activates the aortic arch reflex. -Both of these reflexes are baroreceptor reflexes, and they help keep blood pressure within homeostatic values.

Describe blood flow for capillaries.

-Blood enters cappilaries at their arterial ends and exits the capillaries at their venous ends. -A small amount of fluid moves out of capillaries at their arterial ends and enters other tissues. -Most of that fluid reenters the capillaries at their venous ends. -The remaining fluid enters lymphatic vessels, which eventually return it to the venous circulation. -Alterations in the forces affecting fluid movement across capillary walls are responsible for edema.

Describe blood flow in tissues?

-Blood flow is not equal in all tissues of the body. -Some organs require a greater blood flow than others. -For example, blood flow through the brain, kidneys, and liver is relatively high. -By contrast, blood flow through resting skeletal muscles is not high, but it is greater than that through other tissue types because skeletal muscle constitutes 35-40% of the total body mass. -However, blood flow through exercising skeletal muscles can increase up to 20-fold, and the flow through the viscera, including the kidneys and liver, either remains the same or decreases. -Local control of blood flow is achieved by the periodic relaxation and contraction of precapillary sphincters regulating blood flow through capillary networks of the tissues. -In most tissues, blood flow is proportional to the metabolic needs of the tissue; therefore, as metabolic needs increase, as is the case when the activity of skeletal muscle increases, blood flow increases to supply the greater need for O2 and other nutrients. -Blood flow also increases in response to a buildup of metabolic end products.

What is blood flow in capillary branches regulated by?

-Blood flow is regulated in the capillary branches by precapillary sphincters, smooth muscle cells located at the origin of the branches. -Blood flows through the capillary network into the venues. -The ends of capillaries closest to the arterioles are arterial capillaries, and the ends closet to venues are venous capillaries.

What is blood flow to the tissues controlled by?

-Blood flow provided to the tissues by the circulatory system is highly controlled and matched closely to the metabolic needs of tissues. -Mechanisms that control blood flow through tissues are classified as (1) local control or (2) nervous and hormonal control.

Describe pressure in arteries.

-Blood flow to all areas of the body depends on the maintenance of adequate pressure in the arteries. -As long as arterial blood pressure is adequate, local control of blood flow is appropriately matched to tissues' metabolic needs. -Blood flow through tissues cannot be adequate if arterial blood pressure is too low. -Inadequate blood flow throughout the body due to the failure of mechanisms to maintain normal blood pressure is circulatory shock. -If normal blood pressure is not maintained, damage to the body tissues can lead to death. -On the other hand, if arterial blood pressure is too high, the heart and blood vessels may be damaged.

Describe blood from in capillary network.

-Blood flows from arterioles to capillary networks through metarterioles, vessels with isolated smooth muscle cells along their walls. -Blood then flows from a metarteriole into a thoroughfare channel, a vessel within the capillary network that extends in a relatively direct fashion from a met arteriole to a venue. -Blood flow through thoroughfare channels is relatively continuous. -Several capillaries branch from the thoroughfare channels is relatively continuous. -Several capillaries branch from thoroughfare channels, forming the capillary network.

How can blood pressure be measured?

-Blood pressure can be measured directly by inserting a cannula (tube) into a blood vessel and connecting a manometer or an electronic pressure transducer to it. -Electronic transducers are very sensitive and can precisely detect rapid fluctuations in pressure. -Placing a catheter into a blood vessel or into a chamber of the heart to monitor pressure changes is possible but not appropriate for routine clinical examinations. Health professionals most often use the auscultatory method to measure blood pressure. -They wrap a blood pressure cuff connected to a sphygmomanometer around a patient's arm just above the elbow and place a stethoscope over manometers, and others have digital manometers, but they all measure pressure in terms of millimeters of mercury. -The blood pressure cuff is inflated until the brachial artery is completely collapsed. -Because blood flow through the constricted area is blocked at this point, no sounds can be heard through the stethoscope. -Then the pressure in the cuff is gradually lowered. -As soon as it declines below the systolic pressure, blood flows through the constricted area during systole (contraction of the ventricles). -The blood flow is turbulent and produces vibrations in the blood and surrounding tissues that can be heard through the stethoscope. -These sounds are called korotkoff sounds, and the pressure at which a Korotkoff sound is heard represents the systolic pressure. -As the pressure in the blood pressure cuff is lowered still more, the Korotkoff sounds change tone and loudness. -When the pressure has dropped until continuous laminar blood flow is reestablished, the sound disappears completely. -The pressure at which continuous laminar flow is reestablished is the diastolic pressure. -This method for determining systolic and diastolic pressure is not entirely accurate, but its results are within 10% of methods that are more direct.

How does blood pressure change?

-Blood pressure changes as blood moves from one blood vessel type to another. -The left ventricle forcefully ejects blood from the heart into the aorta. -Because the heart's pumping action is pulsatile, the aortic pressure fluctuates between a systolic pressure of 120 mmHg and a diastolic pressure of 80 mm Hg. -As blood flows through the circulation, from arteries through the capillaries and the veins, the pressure falls progressively to a minimum of approximately 0 mm Hg or even slightly lower by the time it returns to the right atrium.

What is blood pressure?

-Blood pressure is a measure of the force blood exerts against blood vessel walls. -An instrument called a mercury (Hg) manometer measures blood pressure in millimeters of mercury (mm Hg). -A blood pressure of 100 mm Hg is great enough to lift a column of mercury 100 mm.

Describe blood pressure within the heart and vessels.

-Blood pressure is approximately 0 mm Hg in the right atrium and approximately 100 mm Hg in the aorta. -However, the pressure in the vessels above and below the heart is affected by gravity. -While a person is standing, the pressure in the venules of the feet can be as much as 90 mm Hg, instead of the usual 10 mm Hg. -Arterial pressure is influenced by gravity to the same degree; thus, the arterial ends of the capillaries can have a pressure of 110 mm Hg rather than 30 mm Hg. -The normal pressure difference between the arterial and the venous ends of capillaries remains the same, so that blood continues to flow through the capillaries. -The major effect of the high pressure in the feet and legs when a person stands for a prolonged time without moving is edema. -Without skeletal muscle movement, the pressure at the venous end of the capillaries increases. -Up to 15-20 % of the total blood volume can pass through the walls of the capillaries into the interstitial spaces of the lower limbs during 15 minutes of standing still.

What drains into the ascending lumbar veins?

-Blood rom the posterior abdominal wall drains into the ascending lumbar veins. -These veins are continuous superiorly with the hemiazygos on the left and the azygos on the right. -Blood from the rest of the abdomen, pelvis, and lower limbs returns to the heart though the inferior vena cava.

What is the most important means by which capillary exchange occurs?

-By far, the most important means by which capillary exchange occurs is diffusion. -Oxygen, hormones, and nutrients, such as glucose and amino acids, diffuse from a higher concentration in capillaries to a lower concentration in the capillaries. -Similar to the diffusion into and out of cells, how a substance moves into and out of the capillaries depends on its solubility characertistics. -Lipid-soluble molecules, such as O2, CO2, steroid-hormones, and fatty acids, diffuse through the plasma membranes of the endothelial cells of the capillaries. -Water-soluble substances, such as glucose and amino acids, diffuse through intercellular spaces or through fenestrations of capillaries. -In a few areas of the body, such as the spleen and liver, the spaces between the endothelial cells are large enough to allow proteins to pass through them. -In other areas, the connections between endothelial cells are extensive, and few molecules pass between the endothelia cells; such is the case in the capillaries of the brain that form the blood-brain barrier. -In these capillaries, mediated transport moves water-soluble substances across the capillary walls. -The endothelial cells of capillaries appear to take up small pinocytic vesicles and transport them across the capillary wall. -However, the pinocytotic vesicles do not appear to be a major means by which molecules move across the capillary wall.

What are the capillary functions in the skin?

-Capillary networks in the dermis of skin have many more thoroughfare channels than capillary networks in cardiac or skeletal muscle. -The major function of the capillaries in these muscle tissues is nutrient and waste product exchange.

Describe capillary walls.

-Capillary walls are the thinnest of all blood vessels. Recall that one of the four layers of the tunica intima is an internal lignin of simple squamous endothelial cells called the endothelium. -In the vessels associated with the heart, this endothelial lining is continuous with the endocardium of the heart. -Most of the exchange that occurs between the blood and interstitial spaces occurs across the thin walls of capillaries. -The capillary wall consists primarily of a single layer of endothelial cells that rests on a basement membrane. -Outside the basement membrane is a delicate layer of loose connective tissue that merges with the connective tissue surrounding the capillary.

How does chronic hypertension affect the heart?

-Chronic hypertension has an adverse effect on the function of both the heart and the blood vessels. -Hypertension requires the heart to work harder than normal. -This extra work leads to hypertrophy of the cardiac muscle, especially in the left ventricle, and can result in heart failure. -Hypertension also increases the rate at which arteriosclerosis develops. -Arterisclerosis, in turn, increases the probability that blood clots, or thomboemboli will form and that blood vessels will rupture. -Common medical problems associated with hypertension are cerebral hemorrhage, coronary infarction, hemorrhage of renal blood vessels, and poor vision caused by burst blood vessels in the retina.

What are continuous capillaries?

-Continuous capillaries are approximately 7-9 micrometers in diameter, and their walls exhibit no gaps between the endothelial cells. -Continous capillaries are less permeable to large molecule than are other capillary types; they are in muscle, nervous tissue, and many other locations.

Explain why the short-term regulation of blood pressure is important?

-Each of the four short-term regulatory mechanisms of blood pressure are important for specific circumstances. -In most circumstances throughout the day, the baroreceptor reflex is the most important short-term regulatory mechanism for maintaining blood pressure. -The adrenal medullary mechanisms plays a role during exercise and emergencies. -The chemoreceptor mechanism is more important when blood O2 levels are reduced, such as at high altitudes or when CO2 is elevated or pH is reduced. -Thus, it is more important in emergency situations. -The CNS ischemic response is activated only in rare, emergency conditions when the brain receives too little O2.

What does the exchange of fluid across the capillary wall and movement cause?

-Exchange of fluid across the capillary wall and movement of fluid into lymphatic capillaries keep the volume of the interstitial fluid within a narrow range of values. -Disruptions in the movement of fluid across the wall of the capillary can result in edema, or swelling, as a result of increased interstitial fluid volume.

What does figure 21.36 illustrate?

-Figure 21.36 illustrates the interactions between the various pressures that move fluid into and out of the blood. -Using equation (21.6), the net filtration pressure at the arterial end of the capillary is calculated. -The net hydrostatic pressure, which moves fluid out of the capillary, is greater than the net osmotic pressure, which moves fluid into the capillary. -As a result of these differences, there is a net movement of fluid out of the capillary at the arterial end of the capillary.

What is laminar flow?

-Fluid, including blood, tends to flow through long, smooth-walled tubes in a streamlined fashion called laminar flow. -Fluid behaves as if it were composed of a large number of concentric layers. -The movement of these layers is not the same because of the effect of resistance. -The layer nearest the wall of the tube experiences the greatest resistance to flow because it moves against the stationary wall. -The inner most layers slip over the surface of the outermost layers and experience less resistance to movement. -Thus, flow in a vessel consists of movement of concentric layers, with the outer layer moving most slowly and the layer at eh center moving most rapidly. -This is similar to water flow in a river, where the movement of water is fastest toward the more central area of the river and slower near the shoreline.

What is the vasa vasorum?

-For arteries and veins than 1 mm in diameter, nutrients cannot diffuse from the lumen of the vessel to all the layers of the wall. -Therefore, nutrients are supplied to their walls by way of small blood vessels called vasa vasorum, which penetrate from the exterior of the vessel to form a capillary network in the tunica adventitia and the tunica media.

What is hypertension?

-Hypertension, or high blood pressure, affects nearly 30% of the population at sometime in their lives. -Generally, a person is considered hypertensive if the systolic blood pressure is greater than 130 mm Hg and the diastolic pressure is greater than 80 mm Hg. -However, current methods of evaluation take into consideration diastolic and systolic pressures in determining whether a person is suffering from hypertension.

What is one important factor that is influenced by veins?

-In chapter 20, factors that affect cardiac output were described. -One important factor that is influenced by veins is the preload, which is determined by the volume of blood that enters the heart from the veins. -Therefore, the factors that affect flow in the veins are of great importance to the overall function of the cardiovascular system. -If the volume of blood is increased because of rapid transfusion, the amount of blood flow to the heart through the veins increases. -This increases the preload, which causes the cardiac output to increase because of the Starling law of the heart. -On the other hand, rapid loss of a large volume of blood decreases venous return to the heart, which decreases the preload and cardiac output.

Describe fenestrated capillaries.

-In fenestrated capillaries, endothelial cells have numerous fenestra. -The fenestra are areas approximately 70-100 nm in diameter in which the cytoplasm is absent and the plasma membrane consists of a porous diaphragm that is thiner than the normal plasma membrane. -In some capillaries, the diaphragm is not present.

Describe the walls of medium and large veins.

-In medium and large veins, the tunica intima is thin and consists of endothelial cells, a relatively thin layer of collagenous connective tissue, and a few scattered elastic fibers. -The tunic media is also thin and is composed of a thin layer of circularly arranged smooth muscle cells containing some collagen fibers and a few sparsely distributed elastic fibers. -The tunica adventitia, which is composed of collagenous connective tissue, is the predominant layer.

Describe the function of blood flow.

-In some tissues, blood flow serves purposes other than delivering nutrients and removing waste products. -In the skin, blood flow dissipates heat from the body. -In the kidneys, it eliminates metabolic waste products, regulates water balance, and controls the pH of body fluids. -Among other functions, blood flow delivers nutrients that enter the blood from the small intestine to the liver for processing.

What course do the deep veins follow?

-The deep veins draining the upper limb follow the same course as the arteries. -Thus, the radial and ulnar veins are named for the arteries they attend. -They are usually paired, with one small vein lying on each side of the artery, and they have numerous connections with one another with the superficial veins.

Describe the baroreceptors in the carotid sinus and the aortic arch.

-In the carotid sinus and the aortic arch, the arterial walls are partially stretched by normal blood pressure, so that the baroreceptors produce a constant but low frequency of action potentials. -Increased pressure in the blood vessels stretches the vessel walls more, increasing the frequency of action potentials produced by the baroreceptors. -Conversely, a decrease in blood pressure reduces the stretch of the arterial wall, causing a decrease in the frequency of action potentials produced by the baroreceptors. -A sudden increase in blood pressure causes the action potential frequency produced in the baroreceptors to also increase. -In response to these changes, the vasomotor center in the medulla oblongata of the brain decreases sympathetic stimulation of blood vessels, and the cardioregulatory center, also in the medulla oblongata, increases parasympathetic stimulation of the heart. -As a result, peripheral blood vessels dilate, heart rate decreases, and blood pressure decreases.

Why is O2 important to tissue?

-Lack of O2 and nutrients can also be important in regulating blood flow in tissues. -For example, O2 and nutrients are required to maintain vascular smooth muscle contraction. -An increased rate of metabolism decreases the amount of O2 and nutrients in the tissues. -Smooth muscle cells of the precapillary sphincter relax in response to lower levels of O2 and nutrients, resulting in vasodilation.

What is turbulent flow?

-Laminar flow is interrupted and becomes turbulent flow when the rate of flow exceeds a critical velocity or when the fluid passes a constriction, a sharp turn, or a rough surface. -Turbulent flow is caused by numerous small currents flowing at an angle to the long axis of the vessels. -These small currents result in flowing whorls or eddy currents int eh blood vessel. -Vibration of the liquid and blood vessel walls during turbulent flow cause the sounds heard when blood pressure is measured using a blood pressure cuff. -Turbulent flow is also common as blood flows past the valves in the heart and is partially responsible for the heart sounds.

Describe long-term (slow-acting) regulation of blood pressure.

-Long-term (slow-acting) regulation of blood pressure involves the regulation of blood concentration and volume by the kidneys, the movement of fluid across the wall of blood vessels, and alterations in the volume of the blood vessels. -Some of the long-term regulatory mechanisms begin to respond in minutes, but they continue to function for hours, days, or longer. -They adjust blood pressure precisely and keep it within a narrow range of values for years. -Major regulatory mechanisms include (1) the renin-angiotensin-aldosterone mechanism, (2) the antidiuretic hormone (vasopressin) mechanism, (3) the atrial natriuretic mechanism, (4) the fluid shift mechanism, and (5) the stress-relaxation response.

Describe how blood flow changes.

-Major changes in blood flow through blood vessels are produced by changes in blood pressure and blood vessel diameter. -During exercise, heart rate and stroke volume increase, causing blood pressure in the aorta to increase. -In addition, blood vessels in skeletal muscles vasodilator, and resistance to flow decreases. -As a consequence, a dramatic increase in blood flow through blood vessels in exercising skeletal muscles occurs.

What veins in the forearm and hand can be seen through the skin?

-Many of the tributaries of the cephalic and basilica veins in the forearm and hand can be seen through the skin. -Because of the considerable variation in the tributary veins of the forearm and hand, they often are left unnamed.

What is Mean arterial pressure (MAP)?

-Mean arterial pressure (MAP) is slightly less than the average of systolic and diastolic pressures because diastole last longer than systole. -MAP changes over a person's lifetime. -It is approximately 70 mm Hg at brith, slightly less than 100 mm Hg from adolescence to middle age, and 110-130 mm Hg in healthy older persons. -MAP is proportional to cardiac output times peripheral resistance. -Cardiac output (CO) is the volume of blood pumped by the heart each minute. -It is equal to the heart rate (HR) times the stroke volume (SV). -Peripheral resistance (PR) is the resistance to blood flow in all the blood vessels. -MAP is mathematically represented as MAP= CO x PR or MAP= HR x SV x PR

Describe the size of capillaries.

-Most capillaries range from 7 micrometers to 9 micrometers in diameter, and they branch without changing in diameter. -Capillaries are variable in length, but in general they are approximately 1 mm long.

Describe Nervous and Hormonal Control of Blood Flow in Tissues.

-Nervous control of arterial blood pressure is important in the minute-to-minute regulation of blood flow in tissues. -The blood pressure must be adequate to cause blood to flow through capillaries while at rest, during exercise, or in response to circulatory shock, during which blood pressure becomes very low. -For example, during exercise, increased arterial blood pressure is needed to sustain increased blood flow through the capillaries of skeletal muscles, in which precapillary sphincters have dilated. -The increased blood flow supplies increased levels of O2 and nutrients to the exercising skeletal muscles.

What does nervous regulation provide?

-Nervous regulation also provides a means to regulate blood flow by altering the volume of blood flowing to different regions of the body. -For example, in response to blood loss, blood flow to the viscera and the skin is reduced dramatically. -This helps maintain the arterial blood pressure within a range sufficient to allow adequate blood flow through the capillaries of the brain and cardiac muscle.

Describe nervous regulation by the autonomic nervous system in blood vessels.

-Nervous regulation by the autonomic nervous system, particularly the sympathetic division, can function rapidly (within 1-30 seconds). -Sympathetic vasomotor fibers are neurons that regulate the level of smooth muscle contraction in vessel walls. -Because of their control of vasoconstriction, these fibers are referred to as vasoconstrictor fibers. -These fibers innervate all the blood vessels of the body expect the capillaries, the precapillary sphincters, and most metarterioles. -The innervation of the small arteries and arterioles allows the sympathetic nervous system to increase or decrease resistance to blood flow. -Though sympathetic fibers extend to most parts of the circulatory system, sympathetic innervation of blood vessels is not the same in all tissues of the body. -Sympathetic vasoconstrictor fibers are less prominent in skeletal muscle, cardiac muscle, and the brain and more prominent in the kidneys, the digestive tract, the spleen, and the skin.

How is Net hydrostatic pressure determined?

-Net hydrostatic pressure is determined by two hydrostatic pressures: (1) capillary hydrostatic pressure (CHP), which is the blood pressure within the capillaries; and (2) interstitial fluid hydrostatic pressure (IHP), which is the hydrostatic pressure exerted by the interstitial fluid of the tissue surrounding the capillaries. -CHP at the arterial end of a capillary is about 30 mm Hg. -This pressure results mainly from the force of contraction of the heart, but it can be modified by the effect of gravity on fluids within the body (see "Blood Pressure and the Effect of Gravity," later in this section).

What is net osmotic pressure?

-Net osmotic pressure is the difference in osmotic pressure between the blood and the interstitial fluid. -Solutes, such as proteins in the blood and interstitial fluids, will greatly affect the osmotic pressure. -Blood colloid osmotic pressure (BCOP) is caused by plasma proteins in the blood. -Interstitial colloid osmotic pressure (ICOP) is caused by proteins in the interstitial fluid. -Large proteins do not pass freely through the capillary walls, and the difference in protein concentrations between the blood and the interstitial fluid is responsible for osmosis across the capillary wall. -Ions and small molecules do not make a significant contribution to osmosis across the capillary wall because they pass freely through it and their concentrations are approximately the same in the blood as in the interstitial fluid. -The BCOP (28 mm Hg) is several times larger than the ICOP (8mm Hg) because of the presence of albumin and other proteins in the plasma. -For demonstration purposes, we can calculate the net osmotic pressure using equation (21.8): Net osmotic pressure = BCOP - ICOP = 28-8 = 20 mm Hg -The greater the osmotic pressure of a fluid, the greater the tendency for water to move into that fluid. -The net osmotic pressure results in the osmosis of water into the capillary because water has a greater tendency to move into the blood than into the interstitial fluid.

Describe how ADH secretion may occur.

-Neurons of the hypothalamus are sensitive to changes in the solute concentration of the plasma. -Even small increases in solute concentrations directly stimulate hypothalamic neurons that increase ADH secretion. -Increases in the concentration of the plasma, as occur during dehydration, and decreases in blood pressure, as happens after plasma loss, such as in extensive burns or crush gin injuries, stimulate ADH secretion.

Why is NFP at the arterial end of the capillary?

-Note that in the discussion so far, we have referred to the NFP at the arterial end of the capillary. -This is because NFP changes as blood flows through the capillary, primarily due to changes in the net hydrostatic pressure. -The CHP decreases as blood moves through the capillary. -The decrease is from about 30 mm Hg at the arterial end of the capillary to 10 mm Hg at the venous end of the capillary. -This causes a reduction in the net hydrostatic pressure moving fluid out of the venous end of the capillary. -Again, we can demonstrate this using equation (21.7): Net hydrostatic pressure = CHP - IHP = 10 - (-3) = 13 mm Hg -The concentration of proteins within capillaries and the concentration of proteins within interstitial fluid do not change significantly because only a small amount of fluid passes from the capillaries into the tissue spaces. -Therefore, the net osmotic pressure moving fluid into capillaries by osmosis is still approximately 20 mm Hg. -The NFP at the venous end is a negative number, which indicates the tendency for fluid to reenter the capillary.

Describe Occlusion of Blood Vessels and Collateral Circulation.

-Occlusion, or blockaded, of a blood vessel leads to an increase in the diameter of smaller blood vessels that bypass the occluded vessel. In many cases, the development of these collateral vessels is marked. -For example, if the femoral artery is occluded, the small vessels that bypass the occluded vessel become greatly enlarged, and an adequate blood supply to the lower limb is often reestablished over a period of weeks. -If the occlusion is sudden and so complete that tissues supplied by a blood vessel suffer from ischemia (lack of blood flow), cell necrosis (death) can occur. -In this instance, collateral circulation does not have a chance to develop before necrosis sets in.

Where can the pulse be felt on the upper limb?

-On the upper limb, a pulse can also be felt in three arteries: (1) the axillary artery in the axilla, (2) the brachial artery on the medial side of the arm slightly proximal to the elbow, and (3) the radial artery on the lateral side of the anterior forearm just proximal to the wrist. -The radial pulse, taken at the radial artery, is traditionally used because it is the most easily accessible artery in the body.

Describe blood flow for the systemic circulation.

-Oxygenated blood entering the heart from the pulmonary veins passes through the left atrium into the left ventricle. -The left ventricle pumps blood into the aorta. -Blood flows from the aorta to all parts of the body.

Describe the excitatory part and inhibitory part of vasomotor center.

-Part of the vasomotor center inhibits vasomotor tone. -Thus, the vasomotor center consists of an excitatory part, which is tonically active, and an inhibitory part, which can induce vasodilation. -Vasoconstriction results from an increase in vasomotor tone, whereas vasodilation results from a decrease in vasomotor tone. -Areas throughout the brain can either stimulate or inhibit the vasomotor center. -For example, the hypothalamus can exert either strong excitatory or strong inhibitory effects on the vasomotor center. -Increased body temperature detected by temperature receptors in the hypothalamus causes vasodilation of blood vessels in the skin. -The cerebral cortex can also either excite or inhibit the vasomotor center. -For example, action potentials that originate in the cerebral cortex during periods of emotional excitement activate hypothalamic centers, which in turn increase vasomotor tone.

What are pathologic arteriovenous anastomoses?

-Pathologic arteriovenous anastomoses can form in areas of the body as a result of injury or tumors. -These abnormal vascular connections allow for the direct flow of blood from arteries to veins. -If they are sufficiently large, pathological arteriovenous anastomoses can lead to heart failure because of the tremendous increase in venous return to the heart.

What is pulse pressure related to?

-Pulse pressure is inversely related to vascular compliance. -As vascular compliance increases, pulse pressure decreases. -Conversely, as vascular compliance decreases, pulse pressure increases. -The vascular compliance decreases as a person ages. -Arteries in older people become less elastic, or arteriosclerotic, causing the pressure in the aorta to rise more rapidly and to a greater degree during systole and to fall more rapidly to its diastolic value. -Thus, for a give stroke volume, systolic pressure and pulse pressure are higher as vascular compliance decreases.

What does resistance to flow affect?

-Resistance to flow also affects the speed at which pressure changes in the different vessels of the body. -For example, resistance is small in the aorta, so the average pressure at the end of the aorta is nearly the same as at the beginning of the aorta, about 100 mm Hg. -The resistance in medium arteries, which are as small as 3 mm in diameter, is also small, so their average pressure is only decreased to 95 mm Hg. -In smaller arteries, however, the resistance to blood flow is greater, by the time blood reaches the arterioles, the average pressure is approximately 85 mmHg. -The resistance to flow is greater in the aterioles than in any other part of the systemic circulation; at their ends, the average pressure is only approximately 30 mm hg. -The resistance is also fairly high in the capillaries. -The blood pressure at the arterial end of the capillaries is approximately 30 mm Hg, and it decreases to approximately 10 mm Hg at the venous end. -Resistance to blood flow in the veins is small because of their relatively large diameter; by the time the blood reaches the right atrium in the venous system, the average pressure has decreased from 10 mm Hg to approximately O mm Hg.

What is scattered along the length of the capillary?

-Scattered along the length of the capillary are pericapillary cells closely associated with the endothelial cells. -These scattered cells lie between the basement membrane and the endothelial cells and are fibroblasts, macrophages, or undifferentiated smooth muscle cells.

What is the secretion of renin dependent on?

-Secretion of renin is dependent on changes in blood pressure. -Decreased blood pressure stimulates renin secretion, and increased blood pressure decreases renin secretion. -The renin-angiotensin-aldosterone mechanism is important in maintaining blood pressure on a daily basis. -It also reacts strongly under conditions of circulatory shock, but it requires many hours to become maximally effective. -Its onset is not as fast as that of nervous reflexes or the adrenal medullary response, but its duration is longer. -Once renin is secreted, it remains active for approximately 1 hour, and the effect of aldosterone lasts much longer (many hours).

What happens in response to a decrease in blood pressure?

-Similarly, a sudden decrease in blood pressure causes the action potential frequency produced by the baroreceptors to also decrease. -In response, the vasomotor center increases sympathetic stimulation of the blood vessels, and the caridoregulatory center increases sympathetic stimulation and decreases parasympathetic stimulation of the heart. -As a result, peripheral blood vessels constrict, heart rate and stroke volume increase, and blood pressure increases.

Describe sinusoidal capillaries.

-Sinusoidal capillaries are larger in diameter than either continuous or fenestrated capillaries, and their basement membrane is less prominent or completely absent. -Their fenestrae are larger than those in fenestrated capillaries, and gaps can exist between endothelial cells. -The sinusoidal capillaries occur in places where large molecules move into the blood, such as endocrine glands.

Describe sinusoids.

-Sinusoids are large-diameter, sinusoidal capillaries. -Their basement membrane is sparse and often missing, and their structure suggests that large molecules and sometimes cells can move readily across their walls between the endothelial cells. -Sinusoids are common in the liver and bone marrow. -Macrophages are closely associated with the endothelial cells of the liver sinusoids.

Describe the size of muscular arteries.

-Smaller muscular arteries range from 40 micrometers to 300 micrometers in diameter. -Those that are 40 micrometers in diameter have approximately three or four layers of smooth muscle in their tunica media, whereas arteries that are 300 micrometers across have essentially the same structure as the larger muscular arteries. -The small muscular arteries are adapted for vasodilation and vasoconstriction.

What conditions leads to hypertension?

-Some condition leading to hypertension include a decrease in functional kidney mass, excess aldosterone or angiotensin production, and increased resistance to blood flow in the renal arteries. -All of these conditions lead to an increase in total blood volume, which causes cardiac output to increase. -Increased cardiac output forces blood to flow through capillaries, causing the precapillary sphincters to constrict. -Thus, increased blood volume increases cardiac output and peripheral resistance, both of which result in greater blood pressure.

What causes atherosclerosis?

-Some investigators propose that atherosclerosis is not a pathological process but an aging or wearing-out process. -Evidence also suggests that arteriosclerosis may be caused by inflammation, possibly a result of autoimmune disease. -Atherosclerosis has been studied extensively, and many risk factors have been associated with the development of atherosclerotic plaques. -These risk factors include being elderly, being a male, being a postmenopausal woman, having a firmly history of atherosclerosis, smoking cigarettes, having hypertensions, having diabetes mellitus, having increased blood LDL and cholesterol levels, being overweight, leading a sedentary lifesystle, and having high blood triglyceride levels.

How do substances cross through capillary walls?

-Substances cross capillary walls by diffusing either (1) through or between the endothelial cells or (2) through fenestrae. -Lipid-soluble substances, such as O2 and CO2, and small, water-soluble molecules readily diffuse through the endothelial cells. -Larger water-soluble substances must pass through the fenestra or gaps between the endothelial cells. -In addition, transport by pinocytosis occurs, but little is known about its role in the capillaries. -The walls of the capillaries are effective permeability barriers because red blood cells and large, water-soluble molecules such as proteins, cannot readily pass through them.

Why are the radial and ulnar named what they are?

-The deep veins draining the upper limb follow the same course as the arteries. -Thus, the radial and ulnar veins are named for the arteries they attend. -They are usually paired, with one small vein lying on each side of the artery, and they have numerous connections with one another and with the superficial veins.

What is vasomotor center and vasomotor tone?

-The degree to which blood vessels are constricted is regulated by centers in the brain. -An area of the lower pons and upper medulla oblongata, called the vasomotor center, is tonically active. -A low frequency of action potentials is transmitted continually through the sympathetic vasoconstrictor fibers. -As a consequence, the peripheral blood vessels are partially constricted, a condition called vasomotor tone.

Arteries: Abdominal Aorta Visceral Branches Upaired Celiac trunk Left gastric

Stomach and esophagus

What is the adrenal medullary mechanism?

-The adrenal medullary mechanism is activated by a substantial increase in sympathetic stimulation of the heart and blood vessels. -Examples of times when this mechanism is activated include large decreases in blood pressure, sudden and substantial increases in physical activity, and other stressful conditions. -The adrenal medullary mechanism results from stimulation of the adrenal medulla by the sympathetic nerve fibers. -The adrenal medulla releases epinephrine and smaller amounts of norepinephrine into the bloodstream. -These neurohormones affect the cardiovascular system in a fashion similar to direct sympathetic stimulation, causing increased heart rate, increased stroke volume, and vasoconstriction in the blood vessels to the skin and viscera. -Epinephrine also causes vasodilation of blood vessels of the heart. -The adrenal medullary mechanism is short-term and rapid-acting. -It responds within seconds to minutes and is usually active for minutes to hours. -Other hormonal mechanisms are long-term and slow-acting. -They respond within minutes to hours and continue to function for many hours to days.

What does the antidiuretic hormone (vasopressin) mechanism work in harmony with?

-The antidiuretic hormone (vasopressin) mechanism works in harmony with the renin-angiotensin-aldosteron mechanism in response to changes in blood pressure. -Baroreceptors are sensitive to changes in blood pressure. -Decreases in blood pressure detected by the baroreceptors result in the release of antidiuretic hormone (ADH) from the posterior pituitary, although the blood pressure must decreases substantially before the mechanism is activated.

How is the aorta divided?

-The aorta is usually divided into three general parts: (1) the ascending aorta, (2) the aortic arch, and (3) the descending aorta. -The descending aorta is further divided into the thoracic aorta and the abdominal aorta.

How does O2 affect the tissues?

-The availability of O2 to a tissue can be a major factor in determining the adjustment of the tissue's vascularity to its long-term metabolic needs. -If O2 is scarce, capillaries increase in diameter and in number but, if O2 levels remain elevated in a tissue, the vascularity decreases.

Describe how baroreceptor reflexes are adaptable.

-The baroreceptor reflexes are short-term and rapid-acting; however they are adaptable, meaning they do not change the average blood pressure in the long run. -The baroreceptors adapt within 1 - 3 days to any new, sustained blood pressure to which they are exposed. -If blood pressure is elevated for more than a few days, as is the case in a person with hypertensions, the baroreceptors adapt to the elevated pressure, and the baroreceptor reflexes do not reduce blood pressure to its original value.

Where does the brachial artery divide?

-The brachial artery divides at the elbow into the ulnar and radial arteries, which form two arches within the palm of the hand: (1) The superficial palmar arch is formed by the ulnar artery and is completed by anastomosing with the radial artery and (2) the deep palmar arch is formed by the radial artery and is completed by anastomosing with the ulnar artery. -This arch is not only deep to the superficial arch but proximal as well.

What is important regulation g blood pressure moment to moment?

-The carotid sinus and aortic arch baroreceptor reflexes are important in regulating blood pressure moment to mount. -When a person rises rapidly from sitting or lying to a standing position, blood pressure in the neck and thoracic regions drops dramatically because of the pull of gravity on the blood. -This reduction can cause blood flow to the brain to become so sluggish that dizziness or loss of consciousness results. -The falling blood pressure activates the baroreceptor reflexes, which reestablish normal blood pressure within a few seconds. -A healthy person may experience only a temporary sensation of dizziness.

What is the central nervous system (CNS) ischemic response.

-The central nervous system (CNS) ischemic response is the increase in blood pressure in response to lack of blood flow to the medulla oblongata of the brain. -The CNS ischemic response does not play an import role in regulating blood pressure under normal conditions. -It functions primarily in response to emergency situations, as when blood flow to the brain is severely restricted or when blood pressure falls below approximately 50 mm Hg. -Reduced blood flow results in decreased O2, increased CO2, and decreased pH within the medulla oblongata. -Neurons of the vasomotor center are strongly stimulated. -As a result, the vasomotor center stimulates vasoconstriction, and blood pressure rises dramatically. -The increase in blood pressure that occurs in response to CNS ischemia increases blood flow to the CNS, provided the blood vessels are intact. -However, if severe ischemia last longer than a few minutes, metabolism in the brain fails because of the lack of O2. -The vasomotor center becomes inactive, and extensive vasodilation occurs in the periphery as vasomotor tone decreases. -Prolonged ischemia of the medulla oblongata leads to a massive decline in blood pressure and ultimately death.

Describe chemoreceptor reflexes.

-The chemoreceptor reflexes help maintain homeostasis by responding to changes in blood composition. -Specifically, these reflexes are stimulated by decreases in blood O2 levels or increases in blood CO2 levels. -Changes in blood CO2 levels cause changes in blood pH. -As blood CO2 levels increase, blood pH decreases. -Conversely, as blood CO2 levels decrease, blood pH increases. -So chemoreceptor reflexes are also stimulated by decreases in blood pH. -Chemoreceptors are located in carotid bodies, small organs approximately 1-2 mm in diameter, which lie near the carotid sinuses, and in several aortic bodies lying adjacent to the aorta. -Afferent nerve fibers pass to the medulla oblongata through the glossopharyngeal nerve (IX) from the carotid bodies and through the vagus nerve (X) form the aortic bodies.

Describe how chemoreceptors help regulate blood pH.

-The chemoreceptors receive an abundant blood supply. -However, when O2 availability decreases in the chemoreceptor cells, the frequency of action potentials increases and stimulates the vasomotor center, resulting in increased vasomotor tone. -The chemoreceptors act under emergency conditions and do not regulate the cardiovascular system under resting conditions. -They normally do not respond strongly unless blood O2 decreases markedly. -The chemoreceptor cells are also stimulate by increased CO2 and decreased blood pH to increase vasomotor tone, which causes the mean arterial pressure to rise. -The elevated mean arterial pressure increases blood flow through tissues in which blood vessels do not constrict, such as the brain and cardiac muscle. -Thus, the reflex helps provide adequate O2 to the brain and the heart when blood O2 levels in the blood decrease.

Describe blood circulating through blood vessels.

-The dynamic of blood circulating through blood vessels are the same as those of water flowing through pipes. -Blood movement through the vessels is determined by (1) flow, (2) resistance, and (3) pressure. -As we will find int he next section, these factors are significant. -Control mechanisms that regulate blood pressure and blood flow through the tissues are critical to the functions of the circulatory system and the homeostasis of the whole body.

Explain the external jugular veins.

-The external jugular veins are more superficial of the two sets, and they drain blood primarily from the posterior head and neck. -The external jugular vein drains into the subclavian vein.

Describe the relation between the internal and external jugular veins.

-The external jugular veins are the more superficial of the two sets, and they drain blood primarily from the posterior head and neck. -The external jugular vein drains into the subclavian vein. The internal jugular veins are much larger and deeper than the external jugular veins. -The internal jugular veins drain blood from the cranial cavity and anterior head, face, and neck.

What is the first vessel to branch from the aortic arch?

-The first vessel to branch from the aortic arch is the brachiocephalic artery.

What is fluid shift mechanism?

-The fluid shift mechanism occurs in response to small changes in pressures across capillary walls. -As blood pressure increases, some fluid is forced from the capillaries into the interstitial spaces. -This movement of fluid helps prevent the development of high blood pressure. -As blood pressure falls, interstitial fluid moves into capillaries, and this fluid movement resists a further decline blood pressure. -Fluid shift is a powerful mechanism by which blood pressure is maintained, because the interstitial volume acts as a reservoir and is in equilibrium with the large volume of intercellular fluid. -The fluid shift mechanism begins to act within a few minutes of a stimulus, but it requires hours to achieve its full functional capacity. -It plays a very important role when dehydration develops over several hours, or when a large volume of saline is administered over several hours.

Describe blood flow through the pulmonary circulation.

-The heart pumps deoxygenated blood from the right ventricle into a short artery (about 5 cm long) called the pulmonary trunk. -The pulmonary trunk then branches into the right and left pulmonary arteries, transporting blood to the right lung and left lung, respectively. -Within the lungs, gas exchange occurs between the air in the lungs and the blood. -Two pulmonary veins exit each lung. -All four of the pulmonary veins carry oxygenated blood to the left atrium.

What is the hepatic portal system?

-The hepatic portal system carries blood drained from capillaries within most of the abdominal viscera, such as the stomach, intestines, and spleen, to a series of dilated capillaries, called sinusoids, in the liver. -This system delivers nutrients and other substances absorbed from the stomach or small intestine to the liver.

What is the hepatic portal system?

-The hepatic portal system carries blood drained from capillaries within most of the abdominal viscera, such as the stomach, intestines, and spleen, to as dries of dilated capillaries, called sinusoids, in the liver. -This system delivers nutrients and other substances absorbed from the stomach or small intestine to the liver.

Describe the innervation of the metarterioles and the precapillary sphincters.

-The innervation of the met arterioles and the precapillary sphincters in capillary is sparse. -Local factors primarily regulate these structures. -As the rate of metabolism increases in a tissue, blood flow through its capillaries increases. -The precapillary sphincters relax, allowing blood to flow into the local capillary network. -Blood flow can increase sevenfold to eightfold as a result of vasodilation of the metarterioles and the relaxation of precapillary sphincters in response to an increased rate of metabolism.

How is the internal jugular vein formed?

-The internal jugular vein is formed primarily as the continuation of the venous sinuses of the cranial cavity. -The venous sinuses are actually spaces within the dura mater surrounding the brain.

Explain the renin-angiotensin-aldosterone mechanism.

-The kidneys increase urine output as the blood volume and arterial pressure increase, and they decrease urine output as the blood volume and arterial pressure decrease. -Increased urine output reduces blood volume and blood pressure, and decreased urine output resists a further decrease in blood volume and blood pressure. -Controlling urine output is an important means by which blood pressure is regulated, and it continues to operate until blood pressure is precisely within its normal range of values. -The renin-angiotensin-aldosterone mechanism helps regulate blood pressure by altering blood volume.

Describe renin release from the kidneys.

-The kidneys release an enzyme, called renin, into the blood from specialized structures called juxtaglomerular apparatuses. -Renin acts on a plasma protein synthesized by the liver, called angiotensinogen to split a fragment off on end. -The fragment, called angiotensin I, contains 10 amino acids. -Another enzyme, called angiotensin-converting enzyme, found primarily in small blood vessels of the lungs, cleaves 2 additional amino acids from angiotensin I to produce a fragment consisting of 8 amino acids, called angiotensin II, or active angiotensin.

Where do the left and right vertebral arteries originate from?

-The left and right vertebral arteries originate from the left and right subclavian arteries, respectively, and pass through the transverse foramina of the cerivical vertebrae. They enter the cranial cavity through the foramen magnum. -Within the cranial cavity, the left and right vertebral arteries both give off arteries to the cerebellum.

What is the basilar artery?

-The left and right vertebral arteries unite to form a single, midline basilar artery. -The basilar artery gives off branches to the pons and the cerebellum.

Describe long-term regulation of blood flow.

-The long-term regulation of blood flow through tissues is matched closely to the tissues' metabolic requirements. -Because of this close association between regulation and metabolic requirements, a tissue's capillary density can change over time. -If the metabolic activity of a tissue increases and remains elevated for an extended period, the diameter and the number of capillaries in the tissue increase, and local blood flow increases. -An example is the increased density of capillaries in the well-trained skeletal muscles of athletes, compared with that in poorly trained skeletal muscles.

What do the nerve fibers branch to form?

-The nerve fibers branch to form plexuses in the tunica adventitia, and nerve terminals containing neurotransmitter vesicles project among the smooth muscle cells of the tunica media. -Synapses consist of several enlargements of each of the nerve fibers among the smooth muscle ells. -Sympathetic stimulation causes blood vessels to constrict; parasympathetic stimulation causes blood vessels in the penis and clitoris to dilate.

What are the neurotransmitters for the vasoconstrictor fibers?

-The neurotransmitter for the vasoconstrictor fibers is norepinephrine, which binds to alpha-adrenergic receptors on vascular smooth muscle cells to cause vasoconstriction. -Sympathetic action potentials also cause the release of epinephrine and norepinephrine into the blood from the adrenal medulla. -These neurohormones are transported in the blood to all parts of the body. -In most vessels, they cause vasoconstriction, but in some vessels, especially those in skeletal muscle, epinephrine binds to beta-adrenergic receptors, which are present in larger numbers, and can cause the blood vessel sin skeletal muscle to dilate.

What controls blood flow in vessels?

-The periodic compression of veins by contracting skeletal muscles forces blood to flow more rapidly through them toward the heart. -The valves in the veins prevent flow away from the hart, so that, when veins are compressed, blood is forced toward the hart. -During exercise, the combination of arterial dilation and compression of the veins by skeletal muscles causes blood to return to the heart more rapidly than under conditions of rest.

What is pulse pressure?

-The pressure wave that we recognize as a pulse is generated by pulse pressure. -Pulse pressure is the difference between systolic and diastolic pressures. -For example, in a healthy, young adult at rest, systolic pressure is approximately 120 mm Hg, approximately 40 mm Hg (=120 mm Hg - 80 mm Hg).

Describe the rate of blood flow through capillaries.

-The rate of blood flow through capillaries is not constant, but fluctuates. -The cyclic fluctuation is the result of vasomotor, the periodic contraction and relaxation of the precapillary sphincters. -Blood flows through the capillaries until the by-products of metabolism are reduced in concentration and until nutrient supplies to precapillary smooth muscles are replenished. -Then the precapillary sphincters constrict and remain constricted until the by-products of metabolism increase and nutrients decrease.

What work simultaneously to help regulate blood pressure?

-The renin-angiotensin-aldosterone, ADH, and atrial natriuretic mechanisms work simultaneously to help regulate blood pressure by controlling urine production by the kidneys. -If blood pressure drops below 50 mm Hg, the volume of urine produced by the kidneys is reduced to nearly zero. -If blood pressure is increased to 200 mm Hg, the urine volume produced is approximately six to eight times greater than normal. -The mechanisms that regulate blood pressure in the long term are summarized in figure 21.46.

What are the short-term mechanisms that regulate blood pressure?

-The short-term, rapidly acting mechanisms controlling blood pressure involve neural and hormonal control mechanisms. -These mechanisms include (1) the baroreceptor reflexes, (2) the adrenal medullary mechanism, (3) chemoreceptor reflexes, and (4) the central nervous system's ischemic response. -Some of these reflex mechanisms operate on a minute-to-minute basis and help regulate blood pressure within a narrow range of values. -Other mechanisms respond primarily to emergency situation.

Describe the layers of arterioles.

-The tunica intima has no observable internal elastic membrane, and the tunica media consists of one or two layers of circular smooth muscle cells. -Arterioles, like the small arteries, are capable of vasodilation and vasoconstriction.

Describe the differences in make up of each vessel layer of elastic arteries.

-The tunica intima of elastic arteries is relatively thick. -The elastic fibers of the internal and external elastic membranes merge and are not recognizable as distinct layers. -The tunica media consists of a meshwork of elastic fibers with interspersed, circular smooth muscle cells and some collage fibers. -The tunica adventitia is relatively thin.

Describe where muscular arteries gets it name.

-The use of muscular in the name of these vessels refers to their thick tunica media.

How does venules transport nutrients?

-The venules collect blood from the capillaries and transport it to small veins, which in turn transport it to medium veins. -Nutrient exchange occurs across the venue walls but, as the walls of the small veins increase in thickness, the degree of nutrient exchange decreases.

What vessel experience change as you age?

-The walls of all arteries undergo changes as people age, although some arteries change more rapidly than other and some people are more susceptible to change. -The most significant change occurs in the large elastic arteries, such as the aorta, in the large arteries that carry blood to the brain, and in the coronary arteries; the age-related changes described here refer to these blood vessel types. -Muscular arteries exhibit age-related changes, but these are less dramatic and seldom disrupt normal vessel function.

What are the walls of most blood vessels innervated by?

-The walls of most blood vessels are richly innervated by unmyelinated sympathetic nerve fibers. -Some blood vessels, such as those in the penis and clitoris are innervated by parasympathetic fibers. -Small arteries and arterioles are innervate to a greater extent than other blood vessel types.

Describe the walls of the muscular arteries.

-The walls of some muscular arteries are relatively thick, compared with their diameter, mainly because the tunica media contains 25-40 layers of smooth muscle. -The tunica intima of the muscular arteries has a well-developed internal elastic membrane. -The tunica adventitia is composed of a relatively thick layer of collagenous connective tissue that blends with the surrounding connective tissue.

When does turbulent flow occur?

-Turbulent flow of blood through vessels occurs primarily in the heart and to a lesser extent where arteries branch. -Sounds caused by turbulent blood flow in arteries are not normal and usually indicate that the artery is abnormally constricted. -Turbulent flow in abnormally constricted arteries may indicate an increased probability that thromboses will develop.

What two major factors in fluency pulse pressure?

-Two major factors influence pulse pressure: (1) stroke volume of the heart and (2) vascular compliance. -Pulse pressure is directly related to stroke volume. -When stroke volume decreases, pulse pressure also decreases; when stroke volume increases, pulse pressure increases. -For example, during exercise, such as running, the stroke volume increases; as a consequence, the pulse pressure also increases. -After running, the pulse pressure gradually returns to its resting value as the stroke volume of the heart decreases.

What are venous sinuses?

-Venous sinuses are similar in structure to the sinusoidal capillaries but even larger in diameter. -They are found primarily in the spleen, and there are large gaps between the endothelial cells that make up their walls.

What is Venous tone?

-Venous tone is a continual state of partial contraction of the veins as a result of sympathetic stimulation. -Increased sympathetic stimulation increases venous tone by causing the veins to constrict more, which forces the large venous volume to flow toward the heart. -Consequently, venous return and preload increase, causing an increase in cardiac output. -Conversely, decreased sympathetic stimulation decreases venous tone, allowing veins to relax and dilate. -As the veins fill with blood, venous return to the heart, preload, and cardiac output decrease.

What are venules?

-Venues are the smallest vein. -Their structure is very similar to that of capillaries in that they are tubes composed of endothelium resting on a delicate basement membrane. -Venules have diameters up to 50 micrometers.

What happens to blood pressure when a person changes position from lying down to standing?

-When a person changes position from lying down to standing, the blood pressure in the veins of the lower limbs increases. -Because of the structure of their walls, the compliance of veins is approximately 24 times greater than the compliance of arteries. -The increased blood pressure causes the distensible (compliant) veins to expand but has little effect on the arteries. -As the veins expand and fill with blood, venous return decreases because less blood is returning to the heart. -As venous return decreases, cardiac output and blood pressure. -If negative-feedback mechanisms do not compensate and cause blood pressure to increase, the delivery of blood to the brain is not adequate to maintain homeostasis, and the person may feel dizzy or even faint.

What major types of control system regulate blood pressure?

-When blood pressure suddenly drops because of hemorrhage or some other cause, the control systems respond by increasing blood pressure to a value consistent with life and by increasing blood volume to its normal value. -Two major types of control systems operate to achieve these responses: (1) those that respond in the short term and (2) those that respond in the long term. -The short-term regulatory mechanisms respond quickly but begin to lose their capacity to regulate blood pressure a few hours to a few days after blood pressure is maintained at homeostatic values. -This occurs because sensory receptors adapt to the altered pressures. -Long-term regulation of blood pressure is controlled primarily by mechanisms that influence kidney function. -Those mechanism do not adapt rapidly to altered blood pressures.

Why is the pulse important?

-You are most likely familiar with the practice of "taking a person's pulse" in a clinical situation. -The pulse is important clinically because health professionals can determine heart rate, rhythmicity, and other characteristics by feeling it. -The pulse can be felt at 10 major locations on each side of the body where large arteries are close the surface.

List the steps of Fluid Exchange Across the Walls of Capillaries.

1. At the arterial end of the capillary, the net filtration pressure is positive because the net hydrostatic pressure is greater than the net osmotic pressure. More fluid moves out of the capillary. 33 mm Hg (Net hydrostatic pressure) -20 mm Hg (Net osmotic pressure) ------------------------- 13 mm Hg (Net Filtration pressure) 2. Approximately nine-tenths of the fluid that leaves the capillary at its arterial end reenters the capillary at its venous end. About one-tenth of the fluid passes into the lymphatic capillaries. 3. At the venous end of the capillary, the net filtration pressure is negative because the net hydrostatic pressure is less than the net osmotic pressure. More fluid moves into the capillary. 13 mm Hg (Net hydrostatic pressure) -20 mm Hg (Net osmotic pressure) ------------------------- -7 mm Hg (Net filtration pressure)

List the steps of Baroreceptor Reflex Control of Blood Pressure.

1. Baroreceptors in the carotid sinus and aortic arch monitor blood pressure. 2. The glossopharyngeal and vagus nerves conduct action potentials to the cardioregulatory and vasomotor centers in the medulla oblongata. 3. increased parasympathetic stimulation of the heart decreases the heart rate. 4. Increased sympathetic stimulation of the heart increases the heart rate and stroke volume. 5. Increased sympathetic stimulation of blood vessels increases vasoconstriction.

List the five functions of the circulatory system.

1. Carries blood 2. Exchanges nutrients, waste products and gases with tissues. 3. Transports substances 4. Helps regulate blood pressure. 5. Directs blood flow to tissues.

List the steps of Chemoreceptor reflex.

1. Chemoreceptors in the carotid and aortic bodies monitor blood O2, CO2, and pH 2. Chemoreceptors in the medulla oblongata monitor blood CO2 and pH. 3. Decreased blood O2, increased CO2, and decreased pH decrease parasympathetic stimulation of the heart, which increases the heart rate. 4. Decreased blood O2, increased CO2, and decreased pH increase sympathetic stimulation of the heart, which increases the heart rate and stroke volume. 5. Decreased blood O2, increased CO2, and decreased pH increases sympathetic stimulation of blood of blood vessels, which increases vasoconstriction.

List the steps of Renin-Angiotensin-Aldosterone Mechanism

1. Kidneys detect decreased blood pressure, resulting in increased renin secretion. 2. Renin converts angiotensinogen, a protein secreted from the liver, to angiotensin I. 3. Angiotensin-converting enzyme in the lungs converts angiotensin I to angiotensin II. 4. Angiotensin II is a potent vasoconstrictor, resulting in increased blood pressure. 5. Angiotensin II stimulates the adrenal cortex to secrete aldosterone 6. Aldosteron acts on the kidneys to increase Na+ reabsorption. As a result, urine volume decreases and blood volume increases, causing blood pressure to rise.

Describe the Local Control of Blood Flow Through Capillary Beds

1. Vasodilation of precapillary sphincters Precapillary sphincters relax as the tissue concentration of O2, and nutrients, such as glucose, amino acids, and fatty acids, decreases. The sphincters also relax as the concentration of vasodilator substances, such as CO2, lactate, adenosine, adenosine monophosphate, adenosine diphosphate, nitric oxide, and K+, increase, and as the pH decreases. 2. Constriction of precapillary sphincters Precapillary sphincters contract as the tissue concentration of O2 and nutrients, such as glucose, amino acids, and fatty acids, increases. The sphincters also contract as the tissue concentration of metabolic by-products, such as CO2, lactate, adenosine, adenosine monophosphate, adenosine diphosphate, nitric oxide and K+, decreases, and as the pH increases.

List the steps of Blood Pressure Measurement

1. When the cuff pressure is high enough to keep the brachial artery closed, no blood flows through it, and no sound is heard. 2. When cuff pressure decreases and is no longer able to keep the brachial artery closed, blood is pushed through the partially open-end brachial artery, producing turbulent blood flow and a sound. Systolic pressure is the pressure at which a sound is first heard. 3. As cuff pressure continues to decrease, the brachial artery opens even more during systole. At first, the artery is closed during diastole, but as cuff pressure continues to decrease, the brachial artery partially opens during diastole turbulent blood flow during systole produces Korotkoff sounds, although the pitch of the sounds changes as the artery becomes more open. 4. Eventually, cuff pressure deceases below the pressure in the brachial artery, and it remains open during systole and diastole. Nonturbulent flow is reestablished, and no sounds are heard. Diastolic pressure is the pressure at which the sound disappears.

Vessels Systemic Large Arteries

8%

Describe the five functions of the circulatory system.

1.Carries blood 2.Exchanges nutrients, waste products, and gases with tissues 3.Transport substances 4.Helps regulate blood pressure 5.Directs blood flow to tissues.

Elevated blood pressure

120-129/80

Normal blood pressure

120/80

Stage 1 hypertension

130-139/80-89

Vessels Systemic Arteries

15%

Vessels Systemic Arterioles

2%

Vessels Systemic Small arteries

5%

Vessels: Systemic Veins

64%

FIGURE 21.6 Capillary Network

A capillary network stems from an arteriole. Blood flows from he arteriole, through metarterioles, through the capillary network, to venues. Smooth muscle cells, called precapillary sphincters, regulate blood flow through the capillaries. Blood flow decreases when the precapillary sphincters constrict and increases when they dilate.

What is a glomus?

A glomus is an arteriovenous anastomosis that consists of arterioles with abundant smooth muscle in their walls. The vessels are branched and coiled and are surrounded by connective tissue sheaths.

Paried: Suprarenal

Adrenal gland

Veins: Inferior Vena Cava Suprarenal

Adrenal gland

Veins: Suprarenal

Adrenal gland

Parietal Branches: Inferior phrenic

Adrenal gland and inferior surface of diaphragm

T.J. and Tyler were building a treehouse. While searching for a board in a pile of used lumber, T.J. stepped on a rusty nail, which penetrated deeply into his foot, causing it to bleed. Neither T.J. nor Tyler wanted to tell their parents about the accident, but after 3 days, T.J. developed septic shock. His foot had become infected, and the infection had spread into his bloodstream. After reading this chapter and recalling information about the structure and function fo the heart, described in chapter 20, explain how T.J.'s blood volume, blood pressure, heart rate, and stroke volume changed due to septic shoock. Also, explain how blood flow in the periphery changed and how it affected T.J.'s appearance. Finally, explain the consequences if T.J.'s blood pressure remained abnormally low for a prolonged period of time.

After reading the Clinical Impact, "Circulatory Shock," in this chapter, we learned that circulatory shock is inadequate blood flow throughout the body. More specifically, septic shock results from infections that cause the release of toxic substances in to the circulatory system that depress heart activity, cause vasodilation, and increase capillary permeability. After T.J. developed septic shock, we would expect his blood volume to decrease as fluid moved from the more permeable capillaries to the interstitial spaces. The reduction in blood volume would lead to a drop in his blood pressure, stimulating the baroreceptor reflex mechanism and subsequently an increase in heart rate. We would also expect T.J.'s stroke volume to decrease with a drop in blood volume. Increased sympathetic stimulation would cause vasoconstriction of blood vessels as T.J.'s body tried to maintain normal blood pressure. With the reduction in blood flow through the skin, T.J. would appear very pale. If T.J.'s blood pressure is not maintained, he could progress to irreversible shock, which is lethal.

Where are all arteries derived from?

All arteries of the systemic circulation are derived directly or indirectly from the aorta.

What are arteries classified as?

Although the arteries form continuum from the largest to the smallest branches, they are normally classified as (1) elastic arteries, (2) muscular arteries, or (3) arterioles.

List major veins that carry blood away from each of the body areas.

Capillaries do not exist individually in tissues but form branching networks.

What separates the tunica media from the tunica adventitia?

An external elastic membrane separates the tunica media from the tunica adventitia. It can be identified at the outer border of the tunica media in some arteries. In addition, a few longitudinally oriented smooth muscle cells occur in some arteries near the tunica intima.

PROCESS FIGURE 21.42 Chemoreceptor reflex

An increase in blood CO2 and a decrease in pH and O2 result in an increased heart rate and vasoconstriction. A decrease in blood CO2 and an increase in blood pH result in a decreased heart rate and vasodilation.

PROCESS FIGURE 21.39 Baroreceptor Reflex Control of Blood Pressure

An increase in blood pressure increases parasympathetic stimulation of the heart and decreases sympathetic stimulation of the heart and blood vessels, resulting in a decrease in blood pressure. A decrease in blood pressure decreases parasympathetic stimulation of the heart and increases sympathetic stimulation of the heart and blood vessels, resulting in an increase in blood pressure.

Veins: Internal Jugular Vein Sigmoid sinus Superior and inferior petrosal sinuses

Anterior portion of cranial cavity

Arteries: Common Carotid Arteries Internal Carotid Anterior cerebral

Anterior portions of the cerebrum; forms the anterior communicating arteries

Arteries: Vertebral Arteries (branches of the subclavian arteries) Anterior spinal

Anterior spinal cord

Arteries: Brachial Arteries (continuation of axillary arteries) Deep brachial

Arm and humerus

What are arteries?

Arteries carry blood away from the heart.

List the types of arteries. Compare the amount of elastic fibers and smooth muscle in each type of artery.

Arteries carry blood away from the heart. Although the arteries form a continuum from the largest to the smallest branches, they are normally classified as (1) elastic arteries, (2) muscular arteries, or (3) arterioles. Elastic arteries have a greater amount of elastic tissue and a smaller amount of smooth muscle in their walls, compared with other arteries. The elastic fibers are responsible for the elastic characteristics of the blood vessel wall, but collagenous connective tissue determines the degree to which the arterial wall can stretch. The walls of some muscular arteries are relatively thick, compared with their diameter, mainly because the tunica media contains 25-40 layers of smooth muscle. The tunica intima has no observable internal elastic membrane, and the tunica media consists of one or two layers of circular smooth muscle cells.

What does arteriosclerosis involve?

Arteriosclerosis involves general hypertrophy fo the tunica intima, including the internal elastic membrane and hypertrophy of the tunica media. -For example, when arteriosclerosis is associated with hypertensions, the amount of smooth muscle and elastic tissue in the arterial walls increases. -The elastic tissue can form concentric layers in the tunica intima, which biomes less elastic. -Also, some of the smooth muscle cells of the tunica media can ultimately be replaced by collagen fibers. -Arteriosclerosiss in the arteries, primarily those of the lower limbs, with little or no encroachment on their lumens. -The calcium deposits reduce the vessels' elasticity.

What are arteriovenous anastomoses?

Arteriovenous anastomoses are specialized vascular connections that allow blood to flow directly from arterioles to small veins without passing through capillaries.

What do capillaries in the skin function as?

Capillaries in the skin function in thermoregulation, and heat loss results from the flow of a large volume of blood through them.

What happens at the arterial end of capillaries?

At the arterial end of capillaries, the net hydrostatic pressure that moves fluid across the capillary walls into the tissue spaces is the difference between CHP and IHP: Net hydrostatic pressure = CHP - IHP =30 - (-3) = 33 mm Hg -In equation (21.7), IHP is a negative number because of the suction effect produced by the lymphatic vessels as they absorb excess fluid from the tissue spaces. -The lymphatic system is described in chapter 22. -Here, it is only necessary to understand that excess interstitial fluid enters lymphatic capillaries and is eventually returned to the blood.

what is the abdominal aorta divided into?

At the level of the fifth lumbar vertebra, the abdominal aorta divides into two common iliac arteries.

What forms the carotid sinus?

At the point of bifurcation on each side of the neck, the common carotid artery and the base of the internal carotid artery are dilated slightly to form the carotid sinus, which is important in monitoring blood pressure (baroreceptor reflex).

What does the common carotid arteries branch into?

At this point, each common carotid artery branches into internal and external carotid arteries.

What is atherosclerosis?

Atherosclerosis is the deposition of material in the walls of arteries to form distinct plaques. -It is a common type of arteriosclerosis. -Like the other types, atherosclerosis is related to age and certain risk factors. -The plaques form when macrophages containing cholesterol accumulate in the tunica intima, and smooth muscle cells of the tunica media proliferate. -After the plaques enlarge, they consist of smooth muscle cells, white blood cells, lipids (including cholesterol), and, in the largest plaques, fibrous connective tissue and calcium deposits. -The plaques narrow the lumens of blood vessels and make their walls less elastic. -Atherosclerotic plaques can become so large that they severely restrict or block blood flow through arteries. -In addition, the plaques are sites of thrombosis and embolism formation.

FIGURE 21.8 Atherosclertoic Plaque in an Artery

Atheroscleroti plaques develop within the tissue of the artery wall.

Where are capillary networks most numerous?

Capillary networks are more numerous and more extensive in highly metabolic tissues, such as in the lungs, liver, kidneys, skeletal muscle, and cardiac muscle.

How are capillaries classified?

Based on these characteristics, capillaries are classified as (1) continuous, (2) fenestrated, or (3) sinusoidal.

Describe blood flow.

Blood always flows from an area of higher pressure to an area of lower pressure; the greater the pressure difference, the greater the rate of flow. -For example, the average blood pressure in the aorta (P1) is greater than the blood pressure in the vessels of the relaxed right atrium (P2). -Therefore, blood flows from the aorta to tissues and from tissues to the right atrium. -This is dependent on the pumping action of the heart, maintaining a pressure gradient throughout the circulatory system. -If the heart should stop contraction, the pressure in the aorta would become equal to that in the right atrium, and blood would not longer flow.

Describe blood entering the liver.

Blood entering the liver through the hepatic portal vein is rich with nutrients collected from small intestine, but it can also contain a number of toxins substances harmful to the body chemically so they can be used by other cells of the body. -The liver cells also help remove toxic substance by altering their structure or making them water soluble, a process called biotransformation. -The water-soluble substances can then be transported int he blood to the kidneys, which excreted them in the urine.

What are capillaries?

Blood flows from arterioles into capillaries, the most common type of blood vessel.

Describe the velocity of blood flow.

Blood flows through the vessels of the body at different velocities. -The velocity of blood flow changes relative to the cross-sectional area of each blood vessel type. -We can determine the cross-sectional area for each individual blood vessel; however, a more useful number is to determine the total cross-sectional area for all blood vessels of a given type. -This can be done by calculating the cross-sectional area of a particular blood vessel type and multiplying each by the number of that type of blood vessel in the body. -For example, only one aorta exists, and it has a cross-sectional area of 5 square centimeters (cm^2). -An individual capillary has a very small cross-sectional area. -However, the total cross-sectional area considers the combined area of all capillaries, which number approximately 10 billion in the body. -So the total cross-sectional area of all capillaries is 2500 cm^2, which is much greater than the cross-sectional area of the aorta.

What is the difference between pulmonary and systemic vessels.

Blood flows to different regions of the body. Specifically Pulmonary travels to the lungs to respirate CO2 and make oxygenated blood. Systemic circulation travels to the body tissues and heart to supply the body with oxygen for adequate function.

FIGURE 21.25 Veins of the Thorax

Blood from structures of the thorax return to the hear through three major veins: the right brachiocephalic vein, the left brachiocephalic vein, and the azygos vein.

FIGURE 21.25 Veins of the Thorax

Blood from structures of the thorax return to the heart through three major veins: the right brachiocephalic vein, the left brachiocephalic vein, and the azygos vein.

Where does blood from the cystic veins drain?

Blood from the cystic veins, which drain the gallbladder, also enters the hepatic veins.

Where is blood from the liver sinusoids collected from?

Blood from the liver sinusoids is collected into central veins, which empty into hepatic veins.

Explain the ascending lumbar veins.

Blood from the posterior abdominal wall drains into the ascending lumbar veins. -These veins are continuous superiorly with the hemiazygos on the left and the azygos on the right. -Blood from the rest of the abdomen, pelvis, and lower limbs returns to the heart through the inferior vena cava.

Describe the posterior intercostal vein.

Blood from the posterior thoracic wall is collected by posterior intercostal veins that drain into the azygos vein on the right side of the thorax and the hemiazygos vein or the accessory hemiazygos vein on the left side of the thorax.

What is blood from the posterior thoracic wall collected by?

Blood from the posterior thoracic wall is collected by posterior intercostal veins that drain into the azygos vein on the right side of the thorax and the hemizaygos vein or the accessory hemiazygos vein on the left side of the thorax.

Describe blood flow.

Blood leaving the heart first passes through arteries. Next, the blood flows through the capillaries, which are the smallest blood vessels. Finally, blood moves through veins as it once again flows into the heart.

What are blood vessels?

Blood vessels are hollow tubes that conduct blood through the tissues of the body.

1. Carries blood.

Blood vessels carry blood from the hear to almost all body tissues and back to the heart.

Veins Brachiocephalic Internal jugular

Brain

Veins: Brachiocephalic Internal jugular

Brain

Arteries: Popliteal (continuation of the femoral artery) Fibular (peroneal)

Calf and propel muscles and ankle

Veins: Internal Jugular Vein Transverse sinus Occipital sinus

Central floor of posterior fossa of skull

Arteries: Basilar Artery (formed by junction of vertebral arteries) Anterior interior cerebellar

Cerebellum

Arteries: Vertebral Arteries (branches of the subclavian arteries) Posterior inferior cerebellar

Cerebellum and fourth ventricle

Arteries: Vertebral Arteries (branches of the subclavian arteries) Superior cerebellar

Cerebellum and midbrain

FIGURE 21.3 Structural Comparison of Blood Vessel Types

Comparison of the tissue composition of (a) elastic arteries, (b) muscular arteries, and (c) medium and large veins.

How is compliance expressed?

Compliance = Increase in volume (mL)/Increase in pressure (mm Hg) -Vessels with a large compliance exhibit a large increase in volume when the pressure increases a small amount. -Vessels with a small compliance do not show a large increase in volume when the pressure increases.

What is compliance?

Compliance is the tendency for blood vessel volume to increase as blood pressure increases. -The more easily the vessel wall stretches, the greater is its compliance. -The less easily the vessel wall stretches, the smaller is its compliance.

Veins: Median cubital

Connects basilica and cephalic veins

Stimulus: Nervous Control Increased physical activity or increased sympathetic activity

Constriction of blood vessels in skin and viscera

Stimulus: Hormonal Control (reinforces increased activity of the sympathetic nervous system) Increased physical activity and increased sympathetic activity, causing release of epinephrine and small amounts of norepinephrine from adrenal medulla

Constriction of blood vessels in skin and viscera; dilation of blood vessels in skeletal and cardiac muscle

Stimulus: Local Control Regulation by Metabolic Need of Tissues Decreased vasodilator substances and a reduced need for O2 and nutrients

Contraction of precapillary sphincters and subsequent decrease in blood flow through capillaries

Stimulus: Local Control Autoregulation Increased blood pressure

Contraction of precapillary sphincters to maintain constant capillary blood flow

Veins: Axillary (continuation of the basilic vein) Ulnar

Deep forearm

Stimulus: Long-Term Local Blood Flow Decreased metabolic activity of tissues over a long period

Decreased diameter and number of capillaries

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Anterior tibial

Deep anterior leg

What veins return blood to the right atrium?

Deoxygenated blood from the body is returned to the right atrium through three major veins: (1) the coronary sinus, returning blood from the walls of the heart (2) the superior vena cava returning blood from the head, neck, thorax, and upper limbs; and (3) the inferior vena cava, returning blood from the abdomen, pelvis, and lower limbs.

Describe the three major openings the right atria receives blood from.

Deoxygenated blood from the body is returned to the right atrium through three major veins: (1) the coronary sinus, returning blood form the walls of the heart (2) the superior vena cava returning blood from the head, neck, thorax, and upper limbs; and (3) the inferior vena cava, returning blood from the abdomen, pelvis, and lower limbs.

Inferior mesenteric

Descending colon and rectum

Veins: Hepatic Portal Inferior mesenteric

Descending colon and rectum

Veins: Inferior Vena Cava Phrenic

Diaphragm

Veins: Phrenic

Diaphragm

Arteries Subclavian Arteries (right subclavian originates form the brachiocephalic artery, and left subclavian originates directly from the aorta) Internal thoracic

Diaphragm, mediastinum, pericardium, anterior thoracic wall, and anterior abdominal wall

Where do the digital arteries branch from?

Digital arteries branch from each of the two palmar arches and unite to form single arteries on the medial and lateral sides of each digit.

Arteries: Politeal (continuation of the femoral artery) Digital

Digits of foot

Arteries: Popliteal (continuation of the femoral artery) Digital

Digits of foot

Stimulus: Nervous Control Increased body temperature detected by neurons of the hypothalamus

Dilation of blood vessels in skin

Stimulus: Nervous Control Decreased body temperature detected by neurons of the hypothalamus

Dilation of blood vessels in skin (protects skin from extreme cold)

Stimulus: Nervous Control Anger or embarrassment

Dilation of blood vessels in skin of face and upper thorax

Arteries: Popliteal (continuation of the femoral artery) Dorsalis pedis

Dorsal of foot

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Dorsal vein of foot

Dorsal of foot

Veins: Deep and superficial palmar venous arches

Drain into superficial and deep veins of the forearm

Veins: Deep and superficial palmar venous arches

Drain into superficial and deep veins of the forearm.

Describe the walls of elastic arteries.

Elastic arteries have a greater amount of elastic tissue and a smaller amount of smooth muscle in their walls, compared with other arteries. The elastic fibers are responsible for the elastic characteristics of the blood vessel wall, but collagenous connective tissue determines the degree to which the material wall can stretch.

Describe elastic arteries.

Elastic arteries have the largest diameters and are often called conducting arteries. Because these vessels are the first to receive blood from the heart, blood pressure is relatively high in the elastic arteries. Also, due to the pumping action of the heart, blood pressure in the elastic arteries fluctuates between higher systolic and lower diastolic values. When stretched, the walls of elastic arteries recoil, preventing drastic decreases in blood pressure.

Arteries: Visceral Branches Esophageal

Esophagus

What does the blood vessel walls consist of?

Except for the capillaries and the smallest veins, called venues, the blood vessel walls consist of three relatively distinct tissue layers. These tissue layers are most evident in the muscular arteries and least evident in the veins.

Where are fenestrated capillaries?

Fenestrated capillaries are in tissues where capillaries are highly permeable, such as the intestinal villi, ciliary processes of the eyes, choroid plexuses of the central nervous system, and glomeruli of the kidneys.

Describe fibular veins.

Fibular veins, or peroneal veins, are also paired in each leg and accompany the fibular arteries. -They empty into the posterior tibial veins just before those veins contribute to the popliteal vein.

Arteries: Brachial Arteries (continuation of axillary arteries) Digital arteries

Fingers

Veins: Digital

Fingers

FIGURE 21.7 Valves

Folds in the tunica intima form the valves of veins, which allow blood to flow toward the heart but not in the opposite direction.

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Dorsal venous arch

Foot

FIGURE 21.35 Blood Pressure in the Major Blood Vessel Types

In small arteries and arterioles, blood pressure fluctuations between systole and diastole are reduced. No fluctuations in blood pressure occur in capillaries and veins.

Arteries: Brachial Arteries (continuation of axillary arteries) Radial

Forearm

Arteries: Brachial Arteries (continuation of axillary arteries) Ulnar

Forearm

Where does blood flow from capillaries?

From capillaries, blood flows into veins, vessels that carry blood toward the heart.

What are the layers of a blood vessel?

From the lumen to the outer wall of the blood vessels, the layers, or tunics, are (1) the tunica intima, (2) the tunica media, and (3) the tunica adventitia

Veins: Hepatic Portal Cystic

Gallbladder

Where are Glomera present?

Glomera are present in large numbers in the sole of the foot, the palm of the hand, the terminal phalanges, and the nail beds.

Arteries: Brachial Arteries (continuation of axillary arteries) Superficial palmar arch

Hand and fingers

Arteries: Brachial Arteries (continuation of axillary arteries) Deep palmar arch

Hand and fingers

3. Transports substances.

Hormones, components of the immune system, molecules required for coagulation, enzymes, nutrients, gases, waste products, and other substances are transported in the blood to all areas of the body.

Describe the veins based on location.

In general, the superficial veins of the limbs are larger than the deep veins, whereas in the head and trunk the opposite is the case. Venous sinuses occur primarily in the cranial cavity and the heart.

Arteries: Popliteal (continuation of the femoral artery) Posterior tibial

Knee and leg

Describe what smaller veins follow.

In a very general way, the smaller veins follow the same course as the arteries, and many are given the same names. The veins, however, are more numerous and more variable. The larger veins often follow a very different course and have names different from the arteries.

Describe veins the follow the same course as arteries.

In a very general way, the smaller veins follow the same course as the arteries, and many are given the same names. the veins, however, are more numerous and more variable. The larger veins often follow a very different course and have names different from the arteries.

What else do the blood vessels do?

In addition to providing the routes for blood movement, the blood vessels participate in regulating blood pressure and determine the degree of blood flow to the body's most active tissues. Blood pressure must be high enough to ensure sufficient blood flow to meet the tissues' metabolic needs. Regulation of both he blood vessels and the heart ensure that homeostatic blood pressure is maintained.

What are portal veins?

In some areas of the body, a capillary network is directly connected to another capillary network by portal veins. -Specifically, portal veins begin in a primary capillary network, extend some distance, and end in a secondary capillary network. -This connection is unique in that there is no pumping mechanism like the heart between he two capillary networks.

Where can the pulse be felt in the lower part of the body?

In the lower part of the body, a pulse can be felt in four locations: (1) the femoral artery in the groin, (2) the popliteal artery just proximal to the knee, (3) the dorsals pedis artery at the ankle, and (4) the postural tibial artery at the ankle.

Stimulus: Long-Term Local Blood Flow Increased metabolic activity of tissues over a long period

Increased diameter and number of capillaries

FIGURE 21.45 Antidiuretic Hormone (Vasopressin) Mechanism

Increases in the osmolality of blood or decreases in blood pressure result in antidiuretic hormone (ADH) secretion. ADH increases water reabsorption by the kidneys, and large amounts of ADH result in vasoconstriction. These changes maintain blood pressure.

Arteries: Parietal Branches: Inferior gluteal

Inferior gluteal region, coccyx, and proximal thigh

Arteries Subclavian Arteries (right subclavian originates form the brachiocephalic artery, and left subclavian originates directly from the aorta) Thyrocervical trunk

Inferior neck and shoulder

Parietal Branches: Median sacral

Inferior vertebrae

Arteries: Common Carotid Arteries Internal Carotid Posterior communicating

Joins the posterior cerebral artery

Paried: renal

Kidney

Veins: Inferior Vena Cava Renal

Kidney

Veins: Renal

Kidney

Arteries: Popliteal (continuation of the femoral artery) Anterior tibial

Knee and leg

Veins: Axillary (continuation of the basilica vein) Cephalic

Lateral arm, forearm, and hand (superficial veins of the forearm and hand are variable)

Veins: Axillary (continuation of the axillary vein) Cephalic

Lateral. arm, forearm, and hand (superficial veins of the forearm and hand are variable)

Veins: Brachiocephalic Hemiazygos

Left side, inferior posterior thoracic wall and posterior abdominal wall; esophagus and mediastinum

Veins: Superior Vena Cava Hemiazygos

Left side, inferior posterior thoracic wall and posterior abdominal wall; esophagus and mediastinum

Veins: Brachiocephalic Accessory hemiazygos

Left side, superior posterior thoracic wall

Veins: Superior Vena Cava Accessory hemizaygos

Left side, superior posterior thoracic wall.

Veins: Inferior Vena Cava Hepatic

Liver

Veins Inferior Vena Cava Hepatic

Liver (see the section "Hepatic Portal System")

Parietal Branches: Common iliac internal iliac

Lower back, hip, pelvis, urinary bladder, vagina, uterus, rectum, and external genitalia.

Parietal Branches: Common iliac External iliac

Lower limb

Veins: Common iliac External iliac

Lower limb

Veins: Inferior Vena Cava Common Iliac External iliac

Lower limb

Parietal Branches: Lumbar

Lumbar vertebrae and back muscles.

Arteries: Visceral Branches Bronchial

Lung tissue

How is the rate of blood flow in a vessel described?

Mathematically, the rate of blood flow in a vessel can be described by equation (21.1) Flow = P1-P2/R where P1 and P2 are the pressures in the vessel at points one and two, respectively, and R is the resistance to flow.

Veins: Basilic

Medial arm, forearm, and hand (superficial veins of the forearm and hand are variable)

Where do medium veins collect blood from?

Medium veins collect blood from small veins and deliver it to large veins.

Describe the amount of valves in a vein.

Medium veins contain many valves, and the number of valves is greater in veins of the lower limbs than in veins of the upper limbs.

Arteries: Common Carotid Arteries External Carotid Posterior auricular

Middle and inner ear, head, and neck

Arteries: Common Carotid Arteries External Carotid Maxillary

Middle and inner ears, meninges, lower jaw and teeth, upper jaw and teeth, temple, external eye structures, face, palate, and nose.

FIGURE 21.38 Nervous Regulation of Blood Vessels

Most blood vessels are innervated by sympathetic nerve fibers. The vasomotor center within the medulla oblongata plays a major role in regulating the frequency of action potentials in nerve fibers that innervate blood vessels.

Arteries: Common Carotid Arteries Internal Carotid Middle cerebral

Most of the lateral surface of the cerebrum

What are the most observed veins in gross anatomical dissections?

Most of the veins observed in gross anatomical dissections are medium veins and large veins.

Arteries: Parietal Branches: Superior gluteal

Muscles of the gluteal region

What are muscular arteries called?

Muscular arteries are frequently called distributing arteries because the smooth muscle cells allow them to partially regulate blood flow to different body regions by either constricting or dilating.

What do muscular arteries include?

Muscular arteries include medium-sized and small arteries.

Arteries: Common Carotid Arteries External Carotid Superior thyroid

Neck, larynx, and thyroid gland

What is Net filtration pressure?

Net filtration pressure (NFP) is the force responsible for moving fluid across capillary walls. It is the difference between net hydrostatic pressure and net osmotic pressure: NFP = Net hydrostatic pressure - Net osmotic pressure -Hydrostatic pressure is the pressure exerted by fluid, such as blood or intesinal fluid. -Osmotic pressure, as defined in chapter 3, is the force required to prevent water from moving by osmosis across a selectively permeable membrane.

2. Exchanges nutrients, waste products, and gases with tissues.

Nutrients and O2 diffuse from blood vessels to cells in all areas of the body. Waste products and CO2 diffuse from the cells, where they are produced, to blood vessels.

Veins: Internal Jugular Vein Cavernous sinus Ophthalmic veins

Orbit

Veins: Internal Jugular Vein Cavernous sinus Ophthalmic veins

Orbit

Veins: Gonadal Ovarian (female)

Ovary

Veins: Inferior Vena Cava Gonadal Ovarian (female)

Ovary

Paried: Gonadal Ovarian (female)

Ovary, ureter, and uterine tube

Veins: Hepatic Portal Pancreatic

Pancreas

Superior mesenteric

Pancreas, small intestine, and colon

What do the parietal branches of the abdominal aorta supply?

Parietal branches of the abdominal aorta supply the blood to the walls and floor of the pelvis; the lumbar, gluteal, and proximal thigh muscles; and the external genitalia.

Arteries: Axillary Arteries (continuation of subclavian) Lateral thoracic

Pectoral muscles, mammary gland, and axilla

Arteries: Axillary Arteries (continuation of subclavian) Thoracoacromial

Pectoral region and shoulder

Veins: Common iliac Internal iliac

Pelvis and its viscera

Veins: Common iliac internal iliac

Pelvis and its viscera

Arteries: Internal Iliac

Pelvis through the branches listed below

Arteries: Popliteal (continuation fo the femoral artery) Medial plantar

Plantar region of foot

Arteries: Popliteal (continuation of the femoral artery) Lateral plantar

Plantar region of foot

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Plantar veins

Plantar region of foot

Veins: Ascending lumbar

Posterior abdominal wall (empties into common iliac, azygos, and hemiazygos veins)

Veins: Inferior Vena Cava Ascending lumbar

Posterior abdominal wall (empties into common iliac, azygos, and hemiazygos veins)

Arteries: Common Carotid Arteries External Carotid Occipital

Posterior head and neck meninges around posterior brain

Arteries: Vertebral Arteries (branches of the subclavian arteries) Posterior cerebral

Posterior portions of the cerebrum

PROCESS FIGURE 21.37 Local Control of Blood Flow Through Capillary Beds

Precapillary sphincters relax and contract to regulate blood flow to tissues to match the tissues' needs.

PROCESS FIGURE 21.36 Fluid Exchange Across the Walls of Capillaries

Pressure differences exist between the inside and the outside of capillaries at their arterial and venous ends.

Arteries: Parietal Branches: Obturator

Pubic region, deep groin muscles and hip joint

What are pulmonary vessels?

Pulmonary vessels transport blood from the right ventricle, through the lungs, and back to the left atrium.

Arteries: Subclavian Arteries (right subclavian originates form the brachiocephalic artery, and left subclavian originates directly from the aorta) Vertebral

Spinal cord and cerebellum form the basilar artery.

What affects the compliance of the vessel?

Recall that veins have thinner walls than arteries. -This difference also affects the compliance of the vessel. -Venous compliance is approximately 24 times greater than arterial compliance. -As venous pressure increases, the volume of the veins increases greatly. -Consequently, veins act as storage areas, or reservoirs, for blood because their large compliance allows them to hold much more blood than other areas of the circulatory system.

Arteries: Visceral Branches: Middle rectal

Rectum

Arteries: Parietal Branches: Interna pudendal

Rectum, external genitalia, and floor of pelvis

What flows through capillaries?

Red blood cells flow through most capillaries single file and are frequently folded as they pass through the smaller-diameter capillaries.

Stimulus: Local Control Regulation by Metabolic Need of Tissues Increased vasodilator substances (e.g., CO2, lactate, adenosine, adenosine monophosphate, adenosine diphosphate, endothelium-derived relaxation factor, K+, decreased pH0 or decreased O2 and nutrients (e.g., glucose, amino acids, fatty acids, and other nutrients) as a result of increased metabolism

Relaxation of precapillary sphincters and subsequent increase in blood flow through capillaries.

Stimulus: Autoregulation Decreased blood pressure

Relaxation of precapillary sphincters to maintain constant capillary blood flow

Veins: Hepatic Portal Splenic

Spleen

Splenic

Spleen and pancreas

FIGURE 21.41 Adrenal Medullary Mechanism

Stimuli that increase sympathetic stimulation of the heart and blood vessels also result in increased sympathetic stimulation of the adrenal medulla and result in epinephrine and some norepinephrine.

Veins: Superior Vena Cava Brachioccephalic Azygos

Right side, posterior thoracic wall and posterior abdominal wall; esophagus, bronchi, pericardium, and mediastinum

Veins: Superior Vena Cava Brachiocephalic Azygos

Right side, posterior thoracic wall and posterior abdominal wall; esophagus, bronchi, pericardium, and mediastinum

Arteries: Parietal Branches: Lateral sacral

Sacrum

Arteries: Axillary Arteries (continuation of subclavian) Subscapular

Scapular muscles

FIGURE 21.4 Capillary

Section of a capillary, showing that it is composed primarily of flattened endothelial cells.

Left gastroepiploic

Stomach

Veins: Hepatic Portal Superior mesenteric

Small intestine and most of the colon

Veins: Hepatic Portal Gastric

Stomach

Veins: Hepatic Portal Gastroomental

Stomach

FIGURE 21.10 Arteries of the Head and Neck

The brachiocephalic artery, the right common carotid artery, and the right vertebral artery supply the head and neck. The right common carotid artery branches from the brachiocephalic artery, and the vertebral artery branches from the subclavian artery.

What are the branches of the abdominal aorta divided into?

The branches of the abdominal aorta, like those of the thoracic aorta, are divided into visceral and parietal parts.

How are the branches of the thoracic aorta divided?

The branches of the thoracic aorta are divided into two groups: (1) the visceral branches supplying portions of the thoracic organs and (2) the parietal branches supplying portions of the thoracic wall.

What do cardiac veins do?

The cardiac veins transport blood from the walls of the heart and return it through the coronary sinus to the right atrium.

What do the cardiac veins transport?

The cardiac veins transport blood from the walls of the heart and return it through the coronary sinus to the right atrium.

What does the cephalic vein empty into?

The cephalic vein empties into the axillary vein then becomes the subclavian vein at the margin of the first rib.

What are the cephalic, basilic, and brachial veins responsible for?

The cephalic, basilica, and brachial veins are responsible for draining most of the blood form the upper limbs.

What are the cephalic, basilic, and brachial veins responsible for?

The cephalic, basilica, and brachial veins are responsible for draining most of the blood from the upper limbs. -Many of the tributaries of the cephalic and basilica veins in the forearm and hand can be seen through the skin. -Because of the considerable variation in the tributary veins of the forearm and hand, they often are left unnamed.

4. Help regulate blood pressure.

The circulatory system and the heart work together to maintain blood pressure within a normal range of values.

What does the circulatory system include?

The circulatory system includes many blood vessels. These blood vessels are organized into two sets: (1) pulmonary vessels and (2) systemic vessels.

5. Directs blood flow to tissues.

The circulatory system regulates the degree of blood flow and therefore the volume of blood to tissues to maintain homeostasis.

Where do the common carotid arteries extend?

The common carotid arteries extend superiorly, without branching, along each side of the neck, from their base of the inferior angle of the mandible.

What do the common iliac arteries divide into?

The common iliac arteries then divide to form the external iliac arteries, which enter the lower limbs, and the internal iliac arteries, which supply the pelvic area.

What is a good analogy for blood vessels?

The complex water systems that move fluid through pipes for the numerous business and homes in a city are actually a good analogy for representing the intricacy and coordinated functions of blood vessels. The heart is the pump that provides the major force causing blood to circulate, and the blood vessels are the pipes that carry blood to the body tissues and back to the heart.

What are the coronary arteries?

The coronary arteries, which are the only branches of the ascending aorta, are described in chapter 20.

What is the decrease in blood pressure proportional to?

The decrease in blood pressure in each part of the systemic circulation is directly proportional to the resistance to blood flow. -In other words, the greater the resistance in a blood vessel, the more rapidly the pressure decreases as blood flows through it. -This resistance to flow is associated with the diameter of the vessel. -As vessel diameter decreases, resistance flow increases. -Vessels with larger diameters have lower levels of resistance; whereas, vessels with smaller diameters have higher levels of resistance.

How is the aorta described?

The descending aorta is described in two parts: (1) the thoracic aorta and (2) the abdominal aorta.

What do the external carotid arteries supply?

The external carotid arteries have several branches that supply the structures of the neck and face.

What is resistance to flow?

The flow of blood, resulting from a pressure difference between the two ends of a blood vessel, is opposed by a resistance to flow. -As such, the degree of blood flow is inversely related to the amount of resistance. -Another way to state this is that as resistance increases, blood flow decreases; conversely, as the resistance decreases, blood flow length, and vessel diameter. -Considering these three factors, resistance can be represented mathematically by equation (21.2): Resistance = 128vl/pieD^4 where v is the viscosity of blood, l is the length of the vessel, and D is the diameter of the vessel -Both 128 and pie are constants and for practical purposes the length of the blood vessel is constant -Thus, the diameter of the blood vessel and the viscosity of the blood determine resistance. -The viscosity of blood changes slowly.

What do glomera help regulate?

The glomera help regulate body temperature by regulating blood flow through the hands and feet. -As body temperature decreases, glomera constrict and less blood flows through them, reducing the rate of heat loss form the body. -As body temperature increases, glomera dilate and more blood flows through them, increasing the rate of heart loss from the body.

What are the only abdominal organs outside the pelvis that drain directly into he inferior vena cava?

The gonads (testes and ovaries), kidneys, and adrenal glands are the only abdominal organs outside the pelvis that drain directly into the inferior vena cava.

What are the only organs that drain directly into the inferior vena cava?

The gonads (testes and ovaries), kidneys, and adrenal glands are the only abdominal organs outside the pelvis that drain directly into the inferior vena cava.

What is the great saphenous vein?

The great saphenous vein is the longest vein of the body. -It originates over the dorsal and medial side of the foot and ascends along the medial side of the leg and thigh to empty into the femoral vein.

What do the hemiazygos and accessory hemiazygos veins veins empty into?

The hemiazygos and accessory hemiazygos veins empty into the azygos vein, which drains into the superior vena cava.

What drains into the superior vena cava?

The hemiazygos and accessory hemiazygos veins empty into the azygos vein, which drains into the superior vena cava.

FIGURE 21.27 Veins of the Hepatic Portal System

The hepatic portal system begins as capillary beds in the stomach, pancreas, spleen, small intestine, and large intestine. The veins of the hepatic portal system converge on the hepatic portal vein, which carries blood to a series of capillaries (sinusoids) in the liver. Hepatic veins carry blood from capillaries in the liver to the inferior vena cava (also see figure 21.26)

FIGURE 21.27 Veins of the Hepatic Portal System

The hepatic portal system begins as capillary beds in the stomach, pancreas, spleen, small intestine, and large intestine. The veins of the hepatic portal system converge on the hepatic portal vein, which carries blood to a series of capillaries (sinusoids) int he liver. Hepatic veins carry blood from capillaries in the liver to the inferior vena cava (also see figure 21.26)

What does the hepatic portal vein also receive blood from?

The hepatic portal vein also receives blood from gastric veins before entering the liver.

Describe the hepatic portal vein.

The hepatic portal vein, the largest vein of the system, is formed by the union of the superior mesenteric vein, which drains the small intestine, and the splenic vein, which drains the spleen.

Where do the hepatic veins empty?

The hepatic veins empty into the inferior vena cava.

FIGURE 21.26 Inferior Vena Cava and Its Tributaries

The hepatic veins transport blood to the inferior vena cava from the hepatic portal system, which ends as a series of blood sinusoids in the liver.

FIGURE 21.26 Inferior Vena Cava and Its Tributaries

The hepatic veins transport blood to the inferior vena cava from the hepatic portal system, which ends as a series of blood sinusoids int eh liver.

FIGURE 21.17 Arteries of the Pelvis and Lower Limb

The internal and external iliac arteries and their branches. The internal iliac artery supplies the pelvis and hip, and the external iliac artery supplies the lower limb through the femoral artery.

FIGURE 21.11 Cerebral Arterial Circle (Circle of Willis)

The internal carotid and vertebral arteries carry blood to the brain. The vertebral arteries join to form the basilar artery. Branches of the internal carotid arteries and the basilar artery supply blood to the brain and complete a circle of arteries around the pituitary gland and the base of the brain called the cerebral arterial circle (circle of Willis).

Where do the internal carotid arteries enter?

The internal carotid arteries enter the cranial cavity through the carotid canals and give off branches, including the middle cerebral arteries and the anterior cerebral arteries.

What do the internal carotid arteries supply?

The internal carotid arteries, together with the vertebral arteries, which are branches of the subclavian arteries, supply the brain.

What does the internal iliac vein drain?

The internal iliac veins drain the pelvis and join the external iliac veins from the lower limbs to form the common iliac veins.

What are the common iliac veins?

The internal iliac veins drain the pelvis and join the external iliac veins from the lower limbs to form the common iliac veins. The two common iliac veins unite to form the inferior vena cava.

What are the internal jugular veins?

The internal jugular veins are much larger and deeper than the external jugular veins. The internal jugular veins drain blood from the cranial cavity and the anterior head, face, and neck.

How is the internal jugular vein formed?

The internal vein is formed primarily as the continuation of the venous sinuses of the cranial cavity. The venous sinuses are actually spaces within the dura mater surrounding the brain.

PROCESS FIGURE 21.44 Renin-Angiotensin-Aldosteron Mechanism

The kidneys detect decreased blood pressure and increase renin secretion. The result is vasoconstriction, increased water reabsorption, and decreased urine volume, changes that maintain blood pressure.

Where do the large veins transport blood?

The large veins transport blood from the medium veins to the heart.

FIGURE 21.1 Histology of a Blood Vessel

The layers, or tunics, of the blood vessel wall are the tunica intima, media, and adventitia. Vasa vasorum are blood vessels that supply blood to the wall of the blood vessel.

What forms the posterior cerebral arteries?

The left and right vertebral arteries branch to form the posterior cerebral arteries, which supply the posterior part of the cerebrum.

What is the median cubital vein?

The median cubital vein is a variable vein that usually connects the cephalic vein or its tributaries with the basilica vein. -In many people this vein is quite prominent on the anterior surface of the upper limb at the level of the elbow (cubital fossa); therefore, it is often used as a site for drawing blood from a patient.

What is the median cubital vein?

The median cubital vein is a variable vein that usually connects the cephalic vein or its tributaries with the basilica vein. -In many people, this vein is quite prominent on the anterior surface of the upper limb at the level of the elbow (cubital fossa); therefore, it is often used as a site for drawing blood from a patient.

What do the middle cerebral arteries supply?

The middle cerebral arteries supply blood to the frontal lobes of the cerebrum.

FIGURE 21.23 Veins of the Upper Limb

The subclavian vein and its tributaries. The major veins draining the superficial structures of the limb are the cephalic and basilica veins. the brachial veins drain the deep structures.

What are the muscular arteries and arterioles capable of?

The muscular arteries and arterioles are capable of constricting or dilating in response to autonomic and hormonal stimulation, altering resistance and blood flow. -If vessels constrict, resistance to blood flow increases, less blood flows through the constricted blood vessels, and blood is shunted to other, nonconstricted areas of the body. -Muscular arteries help control the amount of blood flowing to each body region, and arterioles regulate blood flow through specific tissues. -Constriction of an arteriole decreases blood flow through the local area it supplies, and vasodilation increases blood flow.

What is the descending aorta?

The next part of the aorta is the descending aorta. The descending aorta is the longest part of the aorta and it extends through the thorax in the left side of the mediastinum and through the abdomen to the superior margin of the pelvis.

What do the paired visceral branches of the abdominal aorta supply?

The paired visceral branches of the abdominal aorta supply the kidneys, adrenal glands,and gonads (testes and ovaries).

What do the parietal arteries of the abdominal aorta supply?

The parietal arteries of the abdominal aorta supply the diaphragm and the abdominal wall.

What does the popliteal artery give off?

The popliteal artery gives off the anterior tibial artery just inferior to the knee and then continues as the posterior tibial artery.

What does the posterior tibial artery give off?

The posterior tibial artery gives off the fibular artery, or perineal artery and then gives rise to medial and lateral plantar arteries, which in turn give off digital branches to the toes.

What is the primary function of the circulatory system?

The primary function of the circulatory system is distribution, ensuring that O2, CO2, nutrients, hormones, and other substances are efficiently moved from one area of the body to other areas. -This distribution relies on the constant flow of blood through the circulatory system. -Recall from equation (21.3) that flow is determined by several factors, including pressure. -In this section e will discuss the factors that affect blood flow and blood pressure as well as how blood flow and blood pressure regulate exchange of substances between the blood and other tissues.

What is the pulmonary circulation?

The pulmonary circulation is the system of blood vessels that carries blood from the right ventricle of the heart to the lungs and back to the left atrium of the heart.

What do the radial and ulnar veins empty into?

The radial and ulnar veins empty into the brachial veins, which accompany the brachial artery and empty into the axillary vein.

Where do the radial and ulnar veins empty into?

The radial and ulnar veins empty into the brachial veins, which accompany the brachial artery and empty into the axillary vein.

What are the three major veins that return blood from the thorax?

Three major veins return blood from the thorax to the superior vena cava: (1) the right brachiocephalic vein, (2) the left brachiocephalic vein, and (3) the azygos vein.

How is the rate of blood flow expressed?

The rate at which a liquid, such as blood, flows through a tube can be expressed as the volume that passes a specific point per unit of time. -Blood flow is usually reported in either milliliters (mL) or liters (L) per minute. -For example, when a person is resting, the cardiac output of the heart is approximately 5 L/min; thus, the rate of blood flow through the aorta is approximately 5 L/min. -The rate of blood flow is influenced by pressure differences within the vessel and resistance to flow.

FIGURE 21.18 Major Arteries of the Lower Limb

The relationships among the major arteries of the lower limb are illustrated in the diagram with red arrows indicating the direction of blood flow. Compare this diagram with the anatomical representation in figure 21.17.

FIGURE 21.14 Major Arteries of the Shoulder and Upper Limb

The relationships among the major arteries of the shoulder and upper limb are illustrated in the diagram with red arrows indicating with the anatomical representation.

FIGURE 21.12 Major Arteries of the Head and Thorax

The relationships among the major arteries that supply blood to the structures of the head and thorax are illustrated with the anatomical representations in figures 21.9, 21.10, and 21.11.

FIGURE 21.28 Major Veins of the Abdomen and Pelvis

The relationships among the major veins of the abdomen and pelvis are illustrated in the diagram with blue arrows indicating the direction of blood flow. Compare this diagram with the anatomical representations in figures 21.26 and 21.27

FIGURE 21.22 Major Veins of the Head and Thorax

The relationships among the major veins of the head and thorax are illustrated in the diagram with blue arrows indicating the direction of blood flow. Compare this diagram with the anatomical representation in figures 21.19, 21.20, 21.21, and 21.25.

FIGURE 21.22 Major Veins of the Head and Thorax

The relationships among the major veins of the head and thorax are illustrated in the diagram with blue arrows indicating the direction of blood flow. Compare this diagram with the anatomical representation in figures 21.29, 21.20, 21.21, and 21.25

FIGURE 21.30 Major Veins of the Lower Limb

The relationships among the major veins of the lower limb are illustrated in the diagram with blue arrows indicating the direction of blood flow. Compare this diagram with the anatomical representation in figure 21.29.

FIGURE 21.24 Major Veins of the Shoulder and Upper Limb

The relationships among the major veins of the shoulder and upper limb are illustrated in the diagram with blue arrows indicating the direction of blood flow. The deep veins, which carry far less blood than superficial veins, are indicated by dashed lines. Compare this diagram with the anatomical representation in figure 21.23

FIGURE 21.24 Major Veins of the Shoulder and Upper Limb

The relationships among the major veins of the shoulder and upper limb are illustrated in the diagram with blue arrows indicating the direction of blood flow. The deep veins, which carry far less blood than the superficial veins, are indicated by dashed lines. Compare this diagram with the anatomical representation in figure 21.23

Describe the relation between thickness and composition in blood vessels.

The relative thickness and composition of each layer vary with the diameter of the blood vessel and its type. The transition from one vessel to another is gradual, as are the structural changes.

FIGURE 21.21 Veins of the Head and Neck

The right brachiocephalic vein and its tributaries. The major veins draining the head and neck are the internal and external jugular veins.

FIGURE 21.21 Veins of the Head and Neck

The right brachiocephalicvein and its tributaries. The major veins draining the head and neck are the internal and external jugular veins.

What does the right common carotid artery transport?

The right common carotid artery transports blood to the right side of the head and neck.

FIGURE 21.29 Veins of the Pelvis and Lower Limb

The right common iliac vein and its tributaries

What does the right subclavian artery transport?

The right subclavian artery transports blood to the right upper limb.

What can the saphenous vein be used for?

The saphenous veins can be removed and used as a source of blood vessels for coronary bypass surgery.

What is the second branch of the aortic arch?

The second branch of the aortic arch is the left common carotid artery, which transports blood to the left side of the head and neck.

Where does small saphenous vein begin?

The small saphenous vein begins over the lateral side of the foot and ascends along the posterior leg to the popliteal space, where it empties into the popliteal vein.

How do the smooth muscle cells of a blood vessel act in unison?

The smooth muscle cells of blood vessels act to some extent in unison. Gap junctions exist between adjacent smooth muscle cells; as a consequence, stimulation of a few smooth muscle cells in the vessel wall results in constriction of a relatively large segment of the blood vessel.

What does the splenic vein receive blood from?

The splenic vein receives blood from the inferior mesenteric vein, which drains part of the large intestine, and the pancreatic veins, which drain the pancreas.

Where is the subclavian artery located?

The subclavian artery is located deep to the clavicle.

FIGURE 21.23 Veins of the Upper Limb

The subclavian vein and its tributaries. The major veins draining the superficial structures of the limb are the cephalic and basilica veins. The brachial veins drain the deeps structures.

What is the superficial vein?

The superficial veins consist of the great and small saphenous veins.

What is the systemic circulation?

The systemic circulation is the system of vessels that carries blood from the left ventricle of the heart to the tissues of the body and back to the right atrium.

What is the third branch of the aortic arch/

The third branch of the aortic arch is the left subclavian artery, which transports blood to the left upper limb.

What is the thoracic aorta?

The thoracic aorta is the position of the descending aorta located in the thorax. -It has several branches that supply various structures between the aortic arch and the diaphragm.

Describe the drainage of the brachiocephalic veins.

The thoracic drainage to the brachiacephalic veins is through the anterior thoracic wall by way of the internal thoracic veins. -They receive blood from the anterior intercostal veins.

Describe the thoracic drainage.

The thoracic drainage to the brachiocephalic veins is through the anterior thoracic wall by way of the internal thoracic veins. -They receive blood from the anterior intercostal veins.

What supplies the thoracic walls with blood?

The thoracic walls are supplied with blood by the intercostal arteries, which consist of two sets: 1. The anterior intercostals are derived from the internal thoracic arteries, which are branches of the subclavian arteries. They lie on the inner surface of the anterior thoracic wall. 2. The posterior intercostal are parietal arteries that are derived as bilateral branches directly from the descending aorta. The anterior and posterior intercostal arteries lie along the inferior margin of each rib and anastomose with each other approximately midway between the ends of the ribs. Superior phrenic arteries supply blood to the diaphragm.

What are three major arteries of the upper limb?

The three major arteries of the upper limb are the (1) subclavian artery, (2) axillary artery, and (3) brachial artery.

What is the tunica adventitia?

The tunica adventitia, also called the tunica external, is composed of connective tissue, which varies from dense connective tissue near the tunica media to loose connective tissue that merges with the connective tissue surrounding the blood vessels.

What is the tunica intima?

The tunica intima, also called the tunica interna, is the most internal layer of a blood vessel wall.

Name the three layers of a blood vessel wall. What kinds of tissue are in each layer?

The tunica intima, also called the tunica interna, is the most internal layer of a blood vessel. This tunic consists of four layers: 1. endothelium 2. a basement membrane 3. a thin layer of connective tissue called the lamina propria. 4. a fenestrated layer of elastic fibers called the internal elastic membrane. The internal elastic membrane separates the tunica intima from the next layer, the tunica media. The tunica media, or middle layer, consists of smooth muscle cells arranged circularly around the blood vessels. The tunica media also contains variable amounts of elastic and collagen fibers, depending on the size of the vessel. An external elastic membrane separates the tunica media from the tunica adventitia. The tunica adventitia, also called the tunica external, is composed of connective tissue, which varies from dense connective tissue near the tunica media to loos connective tissue that merges with the connective tissue surrounding the blood vessels.

What else does the tunica media contain?

The tunica media also contains variable amounts of elastic and collagen fibers, depending on the size of the vessel.

What does the tunica media consists of?

The tunica media, or middle layer, consists of smooth muscle cells arranged around the blood vessel.

What are the two anterior cerebral arteries connected by?

The two anterior cerebral arteries are connected to each other by an anterior communicating artery.

What do the two common iliac veins unite to form?

The two common iliac veins unite to form the inferior vena cava.

What do the valves do?

The two folds overlap in the middle of the vein, so that, when blood attempts to flow in a reverse direction, the valves occlude, or block, the vessel.

What are the two major veins that drain blood from the head and neck?

The two pairs of major veins that drain blood from the head and neck are (1) the external jugular veins and (2) the internal jugular veins.

FIGURE 21.2 Comparison of an Artery and a Vein

The typical structure of a medium-sized artery (A) and a vein (V). Note that the artery has a thicker wall than the vein. The predominant layer in the wall of the artery is the tunica media, with its circular layers of smooth muscle. The predominant layer in the wall of the vein is the tunica adventitia, and the tunica media is thinner than in the artery.

What do the valves consist of?

The valves consist of folds in the tunica intima that form two flaps shaped like the semilunar valves of the heart.

Describe the veins of the lower limb

The veins of the lower limb, like those of the upper limb, consist of superficial and deep groups. -The distal deep veins of each limb are paired and follow the same path as the arteries, whereas the proximal deep veins are unpaired.

What is the velocity of blood flow proportional to?

The velocity of blood flow in a particular blood vessel type is inversely proportional to its total cross-sectional area. -The velocity of blood flow is greater in the aorta, but the total cross-sectional area is small. -In contrast, the total cross-sectional area of the capillaries is large, but the velocity of blood flow is low. -As the veins become larger in diameter, their total cross-sectional area decreases, and the velocity of blood flow increases. -The relationship between total cross-sectional area and velocity of blood flow is much like a stream that flows rapidly through a narrow gorge but more slowly through a broad plane.

FIGURE 21.20 Venous Sinuses Associated with the Brain

The venous sinuses of the brain are drainage channels formed from the dura mater. These sinuses transport venous blood and cerebrospinal fluid away from the brain. The venous sinuses empty into the internal jugular veins.

Describe blood flow through the arteries.

The ventricles pump blood from the heart into larger, elastic arteries that branch repeatedly to form many progressively smaller arteries. As they become smaller, the artery walls undergo a gradual transition from having a large amount of elastic tissue and a smaller amount of smooth muscle to having less elastic tissue and more smooth muscle. From these arteries muscle arteries, blood flows into the arterioles, the smallest of the arteries.

What are the visceral arteries divided into?

The visceral arteries are in turn divided into paired and unpaired branches.

What do the visceral branches supply?

The visceral branches supply a portion of the lungs, including the bronchi and bronchioles, as well as the esophagus, and the pericardium. -Even though a large quantity of blood flows to the lungs through the pulmonary arteries, the bronchi and bronchioles requires separate oxygenated blood supply through small bronchial branches from the thoracic aorta.

What is the viscosity of blood influenced by?

The viscosity of blood is influenced largely by hematocrit, which is the percentage of the total blood volume composed of red blood cells. -As the hematocrit increases, the viscosity of blood increase logarithmically. -Blood with a hematocrit of 45% has a viscosity about three times that of water, whereas blood with a very high hematocrit of 65% has a viscosity about seven to eight times that of water. -The plasma proteins have only a minor effect on the viscosity of blood, but dehydration or uncontrolled production of red blood cells can increase the hematocrit and the viscosity of blood substantially. -Viscosity above the normal range increases the workload on the heart. -If this workload is great enough, heart failure can result.

How many types of blood vessels are there?

There are three main types of blood vessels: (1) arteries, (2) capillaries, and (3) veins.

What are the 3 major unpaired branches of the abdominal aorta?

There are three major unpaired branches of the abdominal aorta: (1) the celiac trunk, (2) the superior mesenteric artery, and (3) the inferior mesenteric artery. -Each has several major branches supplying the abdominal organs.

What do the upper limb arteries form?

These arteries form a continuum rather than a branching system.

FIGURE 21.9 Major Arteries

These major arteries carry blood from the heart to the body tissues.

FIGURE 21.19 Major Veins

These veins carry blood from the body tissues to the heart.

FIGURE 21.19 Major Veins

These veins carry blood from tissues to the heart.

What do the vessels form?

These vessels form a continuous passageway for blood flow from the heart, through the body tissues, and back to the heart.

In what direction, relative to the heart, is blood carried by arteries and veins?

These vessels form a continuous passageway for blood flow from the heart, through the body tissues, and back to the heart. Blood leaving the heart first passes through arteries. Next, the blood flows through the capillaries, which are the smallest blood vessels. Finally, blood moves through veins as it once again flows into the heart.

Veins: External Iliac Vein (continuation of the femoral vein) Femoral (continuation of the popliteal vein)

Thigh

Arteries: Femoral

Thigh, external genitalia, and anterior abdominal wall

Arteries: Deep femoral

Thigh, knee, and femur

What does the brachiocephalic artery form?

This short artery branches at the level of the clavicle to form the right common carotid artery and the right subclavian artery.

What does the tunica intima consist of?

This tunic consists of four layers: (1) endothelium, (2) a basement membrane, (3) a thin layer of connective tissue called the lamina propria, and (4) a fenestrated layer of elastic fibers called the internal elastic membrane. The internal elastic membrane separates the tunica intima from the next layer, the tunica media.

Arteries: Parietal Branches Intercostal

Thoracic wall

What three arteries help form the aortic arch?

Three major arteries branch from the aortic arch and carry blood to the head and upper limbs. These arteries are (1) the brachiocephalic artery, (2) the left common carotid artery, and (3) the left subclavian artery.

What are the three portal vein systems?

Three portal vein systems are found in humans: 1. The hepatic portal veins carry blood rom the capillaries in the gastrointestinal tract and spleen to dilated capillaries, called sinusoids, in the liver. 2. The hypothalamohypophysial portal veins carry blood rom the hypothalamus of the brain to the anterior pituitary gland. 3. The renal nephron portal systems are associated with the urine-forming structures of the kidneys.

Veins Brachiocephalic Superior thyroid

Thyroid and deep posterior facial structures (also empties into external jugular)

Veins: Brachiocephalic Superior thyroid

Thyroid and deep posterior facial structures (also empties into external jugular)

Arteries: Common Carotid Arteries

Tissue supplied: Head and neck by branches listed below

How do we illustrate the the total blood volume?

To illustrate this, let's consider the distribution of blood volume in the body. -Approximately 84% of the total blood volume is contained in the systemic blood vessels. -Because of their larger compliance compared to other vessels, veins can hold a larger volume of blood. -So it is not surprising that most of that blood is in the veins (64%). -Smaller volumes of blood are in the arteries (15%) and the capillaries (5%;)

Veins: External Iliac Vein (continuation of the femoral vein) Popliteal Digital veins

Toes

Veins Brachiocephalic Lingual

Tongue and mouth

Veins: Brachiocephalic Lingual

Tongue and mouth

Arteries: Common Carotid Arteries External Carotid Lingual

Tongue mouth, and submandibular and sublingual glands

Explain trauma in the aorta.

Trauma that ruptures the aorta is almost immediately fatal. -Trauma can also lead to an aneurysm, a bulge caused by a weakened spot in the aortic walll -Once the aneurysm forms, it is likely to enlarge and may rupture. -The weakened aortic wall may leak blood slowly into the thorax and must be corrected surgically. -The majority of traumatic aortic arch ruptures occur during automobile accidents when the body is thrown with great force into the steering wheel, the dashboard, or some other object. -This type of injury is effectively prevented by shoulder-type safely belts and air bags.

Arteries: Visceral Branches: Uterine

Uterus, vagina, uterine tube, and ovary

Arteries: Visceral Branches: Vaginal

Vagina and uterus

What is vasoconstriction?

Vasoconstriction results from smooth muscle contraction and causes a decrease in blood vessel diameter, thereby decreasing blood flow through the vessel.

What is vasodilation?

Vasodilation results from smooth muscle relaxation and causes an increase in blood vessel diameter, thereby increasing blood flow through the vessel.

How are veins classified?

Veins are classified by size as (1) venules, (2) small veins, or (3) medium or large veins.

What does veins contain?

Veins that have diameters greater than 2mm contain valves, which allow blood to flow toward the heart, but not in the opposite direction.

FIGURE 21.16 Major Arteries of the Abdomen and Pelvis

Visceral branches include those that are unpaired (celiac trunk, superior mesenteric, and inferior mesenteric) and those that are paired (renal, suprarenal, testicular, and ovarian). Parietal branches include inferior phrenic, lumbar, and median sacral. The relationship among the arteries of the abdomen and pelvis are illustrated in the diagram with red arrows indicating the direction of blood flow. Compare this diagram with the anatomical representation in figure 21.15

What do visceral branches of the abdominal aorta supply?

Visceral branches of the abdominal aorta supply the pelvic organs, such as the urinary bladder, rectum, uterus, and vagina.

What is viscosity?

Viscosity is a measure of a liquid's resistance to flow. -As the viscosity of a liquid increases, the pressure required to force it to flow also increases. -The viscosity of liquids is commonly determined by considering the viscosity of distilled water as 1 and then comparing the viscosity of the liquids with that. -Using the procedure, whole blood has a viscosity of 3.0-4.5, which means that about three times as much pressure is required to force whole blood through a given tube at the same rate as forcing water through the same tube.

Describe the relation between veins and arteries.

When compared with arteries, the walls of veins are thinner. Vein walls also contain less elastic tissue and fewer smooth muscle cells. -As the blood returned to the heart, it flows through veins with thicker walls and greater diameters.

What are the three types of veins based on location?

When describing the specific veins of the body, we often categorize veins based on location. In that situation, there are three major types of veins: (1) superficial veins, (2) deep veins, and (3) sinuses.

What are the three major types of veins?

When describing the specific veins of the body, we often categorize veins based on location. In that situation, there are three major types of veins: (1) superficial veins, (2) deep veins, and (3) sinuses. -In general, the superficial veins of the limbs are larger than the deep veins, whereas in the head and trunk the opposite is the case. -Venous sinuses occur primarily in the cranial cavity and the heart.

What is Poiseuille's law?

When equation (21.1) (flow) is combined with equation (21.2) (resistance), the following relationship, called Poiseuille's law, results: Flow = P1 - P2/R = pie (P1-P2)D^4/128vl In Poiseuille's law, the value for diameter (D) is raised to the fourth power, so we know that it has a great impact on the overall calculation of flow. -Specifically, a small change in diameter of a vessel dramatically changes the resistance to flow, and therefore the amount of blood that flows through it. -For example, decreasing the diameter of a vessel by half increases the resistance to flow 16-fold and decreases flow 16-fold. -Imagine water flowing from a large tube into a smaller tube. -As the water enters the smaller tube, flow will decrease dramatically. -Vasoconstriction decreases the diameter of a vessel, which increases resistance to flow, and overall, decreases blood flow through the vessel. -Vasodilation increases the diameter of a vessel, which decreases resistance to flow, and increases blood flow through the vessel.

hepatic

liver

right gastric

stomach