A&P 2 chapter 20

Even though individual capillaries are small, there are so many of them they collectively have a very high ______

surface area.

The peak blood pressure measured during ventricular contraction is called the _____, and the minimum blood pressure at the end of the ventricular relaxation phase is called the _____. In recording blood pressure, we separate ____ and _____ with a slash. Average adult blood pressure is 120/80 mmHg.

systolic pressure diastolic pressure systolic diastolic pressure

- As cardiac output increases (as during exercise) blood pressure increases. As cardiac output decreases (as with rest) blood pressure decreases.

Cardiac output

hypovolemic shock in adults is typically caused by _____, although in children it may be caused by fluid losses related to severe vomiting or diarrhea. Other causes for hypovolemic shock include_____, ______, and excessive urine loss related to diabetes insipidus or ketoacidosis. Typically, patients present with a rapid, almost tachycardic heart rate; a weak pulse often described as "thread;" cool, clammy skin, particularly in the extremities, due to _____; rapid, shallow breathing; hypothermia; thirst; and dry mouth. Treatments generally involve providing _____ to restore the patient to normal function and various drugs such as ______, _______ and _____ to raise blood pressure.

-hemorrhage -extensive burns -exposure to some toxins -restricted peripheral blood flow -intravenous fluids -dopamine, epinephrine, and norepinephrine

True capillaries where exchange occurs (about __ to __ per capillary bed).

10 100

The heart generates a pressure of around ___ mmHg as it pumps blood into the aorta which has a cross sectional area of roughly ___ cm2.

100 4.5

At the start of peripheral capillaries, arterial pressure has fallen to approximately ___ mmHg, and by the time blood reaches the venules, it has fallen to approximately ___mmHg.

35 18

By the time blood reaches the vena cavae, pressure is approximately__mmHg.

5

At rest cardiac output averages ____ mL/min. During light exercise, the cardiac output rises, to approximately _____ mL/min, largely due to the increased venous return. During heavy exercise, cardiac output rises toward maximal levels (____ mL/min).

5800 9500 17500

= transport blood away from the heart, generally red, generally transport oxygenated blood.

Arterial System

always carry blood away from the heart to the capillaries, typically red on models because they generally carry oxygenated blood.

Arteries

tend to have a round lumen and relatively thick wall while veins tend to have a flattened, collapsed, or irregularly shaped lumen with relatively thin walls.

Arteries

= also known as resistance vessels; regulate blood flow into capillaries; diameter = .3 mm to 10 micrometers; the tunica media is almost entirely smooth muscle w/ little to no elastin fibers; tunica externa is poorly defined.

Arterioles

may bypass the capillary bed and lead directly to the venous system. These serves as collateral circuits.

Arteriovenous anastomosis

Excessive blood volume or low blood pressure triggers the secretion of ___1___ by the right atrium and __2___ by the muscle cells of the ventricles. __1__ and _2___ both reduce sodium reabsorption so that the body experiences an increase in Na+ loss in urine. Water follows the Na+ so blood volume _____. ANP and BNP inhibit the release of ____, _____, _______, and ______. All of these things together will lower blood pressure.

Atrial natriuretic peptide (or ANP) Brain natriuretic peptide (or BNP) declines ADH aldosterone epinephrine norepinephrine

- the conducting tubes that distribute the blood; three primary types of blood vessels are in the human body. ____ ____ ____

Blood Vessels arteries capillaries veins

= is defined as the amount of force per unit area exerted on the wall of a blood vessel by the blood contained within it. Pressure is measured in ____.

Blood pressure mmHg

= the rate of blood flow through a blood vessel

Blood velocity

On the venous end of the capillary bed, ____has dropped while ____ has remained relatively constant. The net effect is that BCOP is now _____ than CHP and NFP is _____. The negative number indicates a net movement of materials ____ the bloodstream (such as water, wastes, and carbon dioxide).

CHP BCOP greater negative into

- smallest, most abundant type of blood vessel; permits diffusion between the bloodstream and interstitial fluids in order to facilitate nutrient and waste exchange.

Capillaries

=connect arteries to veins and are the site of nutrient and waste exchange. A ____ is a microscopic channel that supplies blood to the tissues themselves, a process called perfusion.

Capillaries

= most abundant; these capillaries possess an uninterrupted layer of squamous cells. The cells are connected by tight junctions and have few intercellular clefts. These are common in skin, muscle, and brain tissues.

Continuous Capillaries

= also known as conducting vessels, found near the heart because they can withstand the highest blood pressures (aorta and its immediate branches); diameter = 2.5 cm to 1 cm; possesses large amounts of elastin fibers in the tunica media forming a "holey sheet" (like Swiss cheese); has substantial smooth muscle in the tunica media, however they have little ability to vasoconstrict.

Elastic arteries

= the endothelial lining of these capillaries possess many pores or "fenestrations" and intercellular clefts. Tight junctions are less numerous. Common in areas where filtration and absorption of dissolved particles is important organ functions. Found in the digestive tract, endocrine glands, kidneys, etc.

Fenestrated Capillaries

= include the superior and inferior venae cavae and their tributaries. All three vessel wall layers are present in all large veins. The slender tunica media is surrounded by a thick tunica externa composed of a mixture of collagen and elastin fibers. Some ______ are flattened with extremely thin walls. These are called _____ and are found in the heart (coronary sinus) and the brain (dural sinuses).

Large veins large veins venous sinuses

- a hollow passageway through which blood flows

Lumen

= range from 2 - 9 mm in diameter; the tunica media is thin and contains smooth muscle cells and collagen fibers. The thickest layer is the tunica externa, which contains smooth muscle cells and longitudinal bundles of elastic and collagen fibers. Valves, particularly within veins of the limbs, are common.

Medium-sized veins

(a vascular shunt) these are the vessels that allow the blood to bypass the true capillaries and be redirected to tissues that need an increased blood supply.

Metarteriole—thoroughfare channels

= also known as distribution vessels; delivers blood to specific body organs (renal artery, mesenteric artery, gastric artery, etc.); diameter = 1 cm to .3 mm; the tunica media has relatively more smooth muscle and less elastin than elastic arteries; very active in vasoconstriction and are less distensible.

Muscular Arteries

Filtration refers to the movement of materials _____ of the bloodstream while reabsorption refers to the movement of materials _____ the bloodstream.

OUT INTO

circular muscles which open and close to allow blood to flow into the true capillary vessels or to bypass them.

Precapillary sphincters

= least common of the three; leaky capillaries because tight junctions are rare and intercellular clefts are abundant. Commonly found in areas where cells must leave circulation and move to the tissues such as bone marrow, liver, and lymph organs. Kupffer cells are specialized phagocytic cells found in the _____ of the liver. They act as macrophages that extend into the lumen of the capillary to capture prey.

Sinusoidal Capillaries

= outermost layer made of connective tissue which serves to anchor, protect, and prevent over-stretching.

Tunica externa (adventitia)

= innermost layer made of simple squamous epithelium called the endothelium and a supporting basement membrane. Large arteries also possess a layer of elastic tissue called the internal elastic membrane.

Tunica interna (intima)

= middle layer which functions in vasodilation and vasoconstriction; composed mostly of smooth muscle, collagen, and elastin fibers. Large arteries also possess an external elastic membrane.

Tunica media

- always return blood from capillaries to the heart; typically blue on models because they generally carry deoxygenated blood

Veins

=transport blood towards the heart, generally blue, and generally transport deoxygenated blood.

Venous System

1. Water, ions, and small organic molecules diffuse between ______ cells or through the pores of the _____

adjacent endothelial fenestrated capillaries.

Epinephrine and norepinephrine = secreted by the medulla of the ______; increases heart rate which in turn increases cardiac output. Increases in cardiac output causes increased blood pressure.

adrenal gland

Aldosterone = secreted by the cortex of the ______; enhances the reabsorption of______ by the kidney which in turn increases water reabsorption by the kidneys and further reduces urine output. With the increase in water in the blood, blood volume increases and blood pressure increases.

adrenal gland sodium ions (Na+)

At each branching of the arterial system, the ____ drops as blood is pushed into ever-increasing numbers of smaller and smaller branches.

arterial pressure

Distributive shock (also known as vascular shock) occurs when _____ lose their normal muscular tone and dilate dramatically. A common cause is ____ (or septicemia), also called "blood poisoning," which is a widespread bacterial infection that results in an organismal-level inflammatory response known as septic shock. ____ shock is a form of vascular shock that occurs with cranial or spinal injuries that damage the cardiovascular centers in the medulla oblongata or the nervous fibers originating from this region. Anaphylactic shock is a severe _____ response that causes the widespread release of _____, triggering vasodilation throughout the body.

arterioles sepsis Neurogenic allergic histamines

In general terms, blood flow (F) is directly proportional to the _____ (increased ____ results in increased_____), and inversely proportional to peripheral resistance (increased resistance results in decreased flow).

blood pressure pressure flow

Renin - Angiotensin II = a drop in _____or _____ is detected by baroreceptors of the kidney. Renin is released and activates angiotensin I (already in the bloodstream) and is converted to the activated angiotensin II, a potent _______. This increases peripheral resistance and blood pressure rises. Plus, angiotensin stimulates the release of other hormones.

blood pressure blood volume vasoconstrictor

factors affecting blood pressure

cardiac output compliance blood volume viscosity of blood peripheral resistance blood velocity

Cardiogenic shock results from the inability of the heart to maintain ____. Most often, it results from a ______(heart attack), but it may also be caused by arrhythmias, _____, cardiomyopathies, _____, or simply insufficient flow of blood through the cardiac vessels. Treatment involves repairing the damage to the heart or its vessels to resolve the underlying cause, rather than treating cardiogenic shock directly.

cardiac output myocardial infarction valve disorders cardiac failure

the cardiovascular centers make extensive adjustments to ___and ____ during changes in physical activity.

cardiac output blood distribution

Changes in blood pressure occur as blood flows through the

cardiovascular system:

Chemoreceptors, located in the _____ and _______; detect changes in blood composition. When the chemoreceptors detect an increase in _____ or a decrease in _____ or pH, they stimulate mechanisms such as vasoconstriction or increased cardiac output and blood pressure.

carotid sinuses aortic arch carbon dioxide oxygen concentration

Baroreceptors, located in the ______, ______, and _____; detect changes in blood pressure. When the baroreceptors detect an increase in blood pressure, they send a signal to the hypothalamus which in turn, triggers ______, a decrease in heart rate, and a reduction in cardiac output. When they detect a decrease in blood pressure, they send a signal to the hypothalamus which in turn, triggers _______, an increase in heart rate, and an increase in cardiac output.

carotid sinuses aorta right atrium vasodilation, vasoconstriction

types of arteries

elastic muscular arterioles

1. Some ions, including Na+, K+, Ca+, or Cl-, can diffuse across _____ by pass through their plasma membrane channels.

endothelial cells

1. Lipids and lipid-soluble materials can cross capillary walls by diffusion through the ________

endothelial plasma membrane.

In the middle of the capillary bed CHP and BCOP are ____ so that NFP = _____. This means there is no _____ and materials are moving in and out equally.

equal Zero net movement

Arteries possess an ________within its tunica media while veins lack an ________

external elastic membrane

Net filtration pressure (or NFP) = the difference between the forces that _____ filtration versus those that _____ it (reabsorption). NFP = CHP - BCOP.

favor oppose

1. Large water-soluble compounds are unable to enter and leave the bloodstream except at ______

fenestrated capillaries.

Capillary exchange is a dynamic process that includes diffusion by _____ and _____mechanisms. Recall that diffusion is the net movement of ions or molecules from an area where their concentration is higher to an area where their concentration is lower.

filtration reabsorption

Vessel diameter = Friction also occurs between layers of ___ moving at different speeds. The layer of blood closest to the vessel wall is slowed down by friction with the _____. The adjacent layer of blood is slowed down by friction with the more _____. As blood proceeds toward the capillaries, the diameter of arteries decreases markedly; as blood returns toward the heart, the diameter of veins ____. This gradually diminishes as the distance from the wall increases. In a small-diameter vessel, all the blood is slowed to some degree and therefore resistance is___. In a large diameter vessel the central region is unaffected by events at the periphery, so the resistance is relatively ___.

fluid endothelial surface superficial layer increases high low

Capillary Hydrostatic Pressure (CHP) = a push out of the bloodstream generated by ______within the vessel.

fluids

1. On the arterial end of the capillary bed, CHP is ____ than BCOP so that NFP is _____. The positive number indicates a net movement of materials ___ of the bloodstream (such as water, nutrients, and oxygen).

greater positive out

filtration is always _____ than reabsorption causing the interstitial fluid to experience a net accumulation of ______and ____. This excess fluid would ______ pressure in the interstitial space and ______ vascular blood pressure if not corrected. Hence, the need for our lymphatic system

greater water materials increase decrease

The cardiovascular control centers are primarily located in the _______ and require the stimulation of _____ and _______. The medulla oblongata can coordinate respiratory activities to enhance control

hypothalamus baroreceptors chemoreceptors

Peripheral resistance - resistance is the amount of opposition (or friction) blood encounters as it flows through the vessels. As resistance increases blood pressure _____. As resistance decreases blood pressure _____. There are several factors affecting resistance and hence blood pressure:

increases decreases

Blood volume - As blood volume increases (as with pregnancy) blood pressure _____. As blood volume decreases (as with hemorrhaging) blood pressure _______. -_______ abnormally high levels of fluid and blood within the body. -_____ abnormally low levels of fluid and blood within the body

increases decreases Hypervolemia - Hypovolemia

Arteries and veins are larger with high ________but they are far less _______ than capillaries so collectively they generate less cross-sectional surface area so blood moves through them_______.

individual surface area numerous faster

1. Blood Colloid Osmotic Pressure (BCOP) = a suction into the bloodstream generated by______

large immovable plasma proteins.

Viscosity of blood = thick fluids are more sluggish than thin fluids. Liquids with low viscosity (like water) flow at _______. Thick, syrupy fluids, such as molasses, flow under _______. Whole blood has a viscosity __-__ times that of water due to the presence of plasma proteins and the formed elements. Increases in viscosity, as when someone is significantly dehydrated, will cause an _____ in blood pressure. A decrease in viscosity will ____ blood pressure.

low pressures higher pressures 4 -5 increase decrease

Circulatory Shock = There are several recognized forms of shock which can occur with the failure to _____or ____:

maintain blood pressure blood flow

Capillary beds are also called "_______".

microcirculation

Compliance - is the ability of any vessel to expand to accommodate increased content. A metal pipe, for example, is not compliant, whereas a balloon is. Veins are ____ compliant than arteries and can expand to hold more blood resulting in ____pressure. When vascular disease causes stiffening of arteries (as with arteriosclerosis), compliance is reduced and resistance to blood flow is _____. The result is higher pressure within the vessel and reduced blood flow.

more less increased reduced

Systemic tissue perfusion occurs along the following path: left ventricle of the heart aorta, elastic and ____ arteries, arterioles, _____, venules, small veins, medium-sized veins, large veins, and finally _____ and inferior vena cava to the right ____ of the heart.

muscular capillaries superior atrium

Because pressure is so low in veins, blood tends to pool in veins and the venous flow depends upon the _____ and _____ to keep the blood moving toward the heart.

muscular pump respiratory pump

Arteries have a tunica externa made of collagen and elastin fibers with a ______ and ____ present. The tunica externa of veins possesses collagen and smooth muscle and the _____ and _____ are present in the tunica externa and the tunica media.

nervi vasorum vasa vasorum nervi vasorum vasa vasorum

Nitric oxide = a potent vasodilator which reduces _____ which in turn, reduces blood pressure.

peripheral resistance

Anti-diuretic Hormone (or ADH) = is secreted by the _______. ADH enhances water reabsorption in the kidney so that urine output is reduced and blood volume rises. Increased blood volume increases______

pituitary gland blood pressure.

The mean arterial pressure (or MAP) is calculated by adding one third of_____to the _____

pulse pressure diastolic pressure.

Systolic pressure - Diastolic pressure =

pulse pressure.

• The difference between systolic and diastolic pressure is the

pulse pressure.

Length versus diameter = Differences in diameter have much more significant effects on _____ than do differences in length. If two vessels are equal in diameter but one is twice as long as the other, the longer vessel offers _____ as much resistance to blood flow. But for two vessels of equal length, one twice the diameter of the other, the narrower one offers __ times as much resistance to blood flow. For this reason, the brain typical initiates changes in blood vessel ______(by vasoconstriction and vasodilation) to regulate blood pressure. However, abnormal narrowing of a vessel due to a _________ (as with atherosclerosis) leads to ________ and increased risk of heart attack (myocardial infarction) and stroke (cerebral vascular accident).

resistance twice 16 diameter plaque buildup hypertension

1. Plasma proteins are normally unable to cross the endothelial lining anywhere except in _____like those of the liver.

sinusoidal capillaries

Capillaries have the highest cross-sectional area and blood traveling through them is therefore very _____.

slow

Structure and general characteristics of capillaries = the smallest of all blood vessels with diameters less than 10 micrometers; composed of a single layer of ______ and a sparse ____. May possess pericytes associate with the epithelium to help stabilize the layer.

squamous epithelium basal lamina

Diffusion occurs continuously across capillary walls, but different _____use different routes and mechanisms for movement into and out of the bloodstream:

substances

Arteries have a____ dominated by smooth muscle and elastic fibers while veins have a ___ composed of smooth muscle and collagen fibers

thick tunica media thin tunica media

The _____ of arteries is rippled and possesses an internal elastic membrane. However the _____of veins is often smooth and the internal elastic membrane is absent.

tunica interna

Structure and general characteristics of arteries = thick ____ compared to tunica externa; lack valves, and may possess large amounts of _____ tissue.

tunica media elastic

->Structure and general characteristics of veins: • Possesses ____ which are formed from folds of the tunica interna function to prevent backflow of blood. If a ___ fails, blood will pool abnormally in the vessel causing it to become grossly distended. If near the surface, it is visible through the skin and is called a varicose vein. Varicose veins of the anal canal are called hemorrhoids. • Serve as ______ (capacitance vessels) because the pressure is so low within these vessels compared to arteries or capillaries. In fact, ___% of blood total volume is in systemic veins at any given time.

valves valve blood reservoirs 64%

Obstructive shock, as the name would suggest, occurs when a significant portion of the _____ is blocked. It is not always recognized as a distinct condition and may be grouped with ____shock. The most common cause is a ______, a clot that lodges in the pulmonary vessels and interrupts blood flow. Other causes include stenosis of the aortic valve; cardiac tamponade, in which excess fluid in the _____ interferes with the ability of the heart to fully relax and fill with blood (resulting in decreased preload); and a pneumothorax, in which an excessive amount of air is present in the thoracic cavity, outside of the lungs, which interferes with venous return, pulmonary function, and delivery of oxygen to the tissues.

vascular system cardiogenic pulmonary embolism pericardial cavity

Arterial pressure is not constant; it rises during _______ and falls during ______ as the elastic arterial walls stretch and recoil.

ventricular contraction ventricular relaxation

types of veins ____ _____ ____

venues medium-sized veins large veins

= drains capillary beds into veins. These are extremely porous and are often more similar in structure and function to capillaries than to veins. Many ____ possess only endothelium and pericytes while others may have scanty tunica media and a thin tunica externa.

venues venules

Vessel length = Friction occurs between the moving blood and the walls of the _____. The longer the vessel length, the greater the surface area in contact with the blood, and therefore the ______ the resistance. The most dramatic changes in blood vessel length occur between birth and adulthood. Once the reach adulthood, vessel length is relatively _____.

vessel greater constant

Blood flow (F), also called tissue perfusion, is defined as the volume of blood flowing through a____, an ____, or the entire circulation.

vessel organ

factors affecting resistance and hence blood pressure:

vessel length vessel diameter Length versus diameter

1. Velocity is inversely proportional to the cross-sectional surface area of the _____; the more surface area - the more _____ - the slower blood flows.

vessels friction