Spring 2016 Chapter 19 Cardiovascular System:Blood Vessels HCC A & P II

Suppose colloid osmotic pressure (OP) in the interstitial fluid (if) rises dramatically - say because of a severe bacterial infection in the surrounding tissue. (a) predict how fluid flow in the change in the situation. (b) Now calculate the NFP (net filtration pressure) at the venous end of the capillary if OPif increases to 10 mm Hg. (c) in which direction does fluid flow at the venous end of the capillary now - in or out?

(a) An increase in interstitial fluid osmotic pressure (OPif) would tend to pull more fluid out of the capillaries (causing localized swelling or edema). (b) An increase in OPif to 10 mm Hg would increase the outward pressure on both the ateriole and venule ends of the capillary. If, before this condition, NFP = (HPc +OPif) - (HPif+OPc) = (17 + 1) - (0+26) = -8 mm Hg (net inward pressure then the equation becomes (17 +10) - (0+26) = +1 mmHg (net outward pressure) (c) Fluid would flow out of the venous end of the capillary rather than in.

Name the type of artery that matches each description: 1) major role in dampening the pulsatile pressure of heart contractions; 2) vasodilation or constriction determines blood flow to individual capillary beds; 3) have the thickest tunica media relative to their lumen size

1) elastic arteries 2) arterioles 3) muscular arteries

Chapter 19 Mr. Hutchinson, another middle-aged victim of the collision on Route 91, has a tourniquet around his thigh when admitted in an unconscious state to Noble Hospital. The emergency technician who brings him in states that his right lower limb was pinned beneath the bus for at least 30 minutes. He is immediately scheduled for surgery.

Admission notes include the following: - multiple contusions of lower limbs - compound fracture of the right tibia;; bone ends covere with sterile gauze - right leg blanched and cold, no pulse - blood pressure 90/48; pulse 140/min and thread; patient diaphoretic (sweaty)

how do venous pressures compare to arterial pressures?

Arterial walls get their pressure via force of the left ventricle pumping into the arteries. Veins are not exposed to such force and get their pressure via muscle pumps.

Describe the role of baroreceptors in the homeostatic control of blood pressure.

Baroreceptors are specialized stretch receptors located within thin areas of blood vessels and heart chambers that respond to the degree of stretch caused by the presence of blood. They send impulses to the cardiovascular center to regulate blood pressure. Vascular baroreceptors are found primarily in sinuses (small cavities) within the aorta and carotid arteries. The aortic sinuses are found in the walls of the ascending aorta just superior to the aortic valve, whereas the carotid sinuses are in the base of the internal carotid arteries. There are also low-pressure baroreceptors located in the walls of the venae cavae and right atrium. When blood pressure increases, the baroreceptors are stretched more tightly and initiate action potentials at a higher rate. At lower blood pressures, the degree of stretch is lower and the rate of firing is slower. When the cardiovascular center in the medulla oblongata receives this input, it triggers a reflex that maintains homeostasis .

Write an equation showing the relationship between peripheral resistance, blood flow, and blood pressure.

Blood Flow = (B.P. 1 - B.P. 2) / Resistance. (p. 702) (B.P. 1 - B.P. 2) = difference in blood pressure between two points in the circulation system

Blood Flow =

Blood Flow = pressure difference resistances or Q = ΔP/ R where Q = flow rate (volume/time); ΔP = pressure difference (mm Hg); and R = resistance to flow (mm Hg x time/volume).

Your neighbor, Bob, calls you because he thinks he is having an allergic reaction to a medication. You find Bob on the verge of losing consciousness and having trouble breathing. When paramedics arrive, they note his BP is 63/38 and he has a rapid, thready pulse. Explain Bob's low BP and rapid HR.

Bob is in vascular shock due to anaphlaxis, a systemic allergic reaction to his medication. His blood pressure is low because of widespread vasodilation triggered by the massive release of histamine. Bob's rapid heart rate is a result of the baroreceptor reflex triggered by his low BP. This activates the sypathetic nervous system, increasing heart rate, in an attempt to restore blood pressure. histamine: a compound that is released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.

CO (Cardiac Output) =

CO (Cardiac Output) = SV (Stroke Volume) x HR (Heart Rate)

factors that affect blood pressure. mark (I) increase or (D) decrease BP: increased diameter of the arterioles_____, increased blood viscosity_____, increased cardiac output_______, hemorrhage_____, artereosclerosis_______, increased pulse rate_______.

D, I, I, D, I, I. factors that affect blood pressure. mark (I) increase or (D) decrease BP: increased diameter of the arterioles___D__, increased blood viscosity__I___, increased cardiac output____I___, hemorrhage__D___, artereosclerosis____I___, increased pulse rate___I____.

If many arterioles in your body dilated at once, you would expect MAP to plummet. What prevents MAP from decreasing during your bicycle race?

Extrinsic mechanisms, primarily the sympathetic nervous system, prevent blood pressure from plummeting by constricting arterioles elsewhere (such as gut, kidneys). In addition, cardiac output increases, which also helps maintain MAP.

Suppose you are in a bicycle race. What happens to the smooth muscle in the arterioles supplying your leg muscles? What is the key mechanism in this case?

In a bicycle race, autoregulation by intrinsic metabolic controls causes arteriolar smooth muscle in your legs to relax, dilating the vessels and supplying more O2 and nutrients to the exercising muscles.

In the systemic circuit, which contains more blood - arteries or veins - or is it the same?

In the systemic circuit, veins contain more blood than arteries.

Describe the baroreceptor reflex changes that occur to maintain blood pressure when you rise from a lying-down to a standing position.

Normally, when you stand up after being seated for a while, the pull of gravity causes about 15-25% of the blood in your body to pool in your lower extremities. This pooled blood does not return to the heart, therefore amount of blood your heart pumps out decreases and your blood pressure drops. When you first stand up MAP (Mean Arterial Pressure) temporarily decreases and this is sensed by your aortic and carotid baroreceptors. Medullary and vasomotor reflexes increase sympathetic and decrease parasympathetic outflow to the heart. Heart rate and contractility increase, increasing cardiac output and therefore MAP. in addition, increased constriction of veins increases venous return, which increases end diastolic volume (EDV), increasing stroke volume (SV) and therefor cardiac output and MAP.

SV (Stroke Volume) =

SV (Stroke Volume) = EDV (End Diastolic Volume) - ESV (End Systolic Volum

Trace the path of the blood through the pulmonary circuit.

The deoxygenated blood leaves the right ventricle into the pulmonary trunk, which divides into the right and left pulmonary arteries. These branches penetrate the right and the left lungs, respectively. These further divide into arterioles that continue into the capillary networks associated with the walls of the alveoli, where the gas exchanges occur between the blood and the air. From these pulmonary capillaries, the blood enters the venules that eventually merge to form veins. Four pulmonary veins, two from each lung, carry the oxygenated blood back to the left atrium.

Explain why the alveoli normally do not fill with fluid.

The epithelial cells of the alveolar membrane are tightly joined so that most ions fail to enter the alveoli. This helps to maintain a relatively high osmotic pressure in the interstitial fluid. Osmosis will then move any water that gets into the alveoli back into the interstitial space. This mechanism prevents excess water from entering the alveoli and helps keep the alveoli from filling with fluid.

The kidneys play an important role in maintaining MAP by influencing with variable? Explain how renal artery obstruction could cause secondary hypotension.

The kidneys help maintain MAP by influencing blood volume. In renal artery obstruction, the blood pressure in the kidney is lower than the rest of the body (because it is downstream of the obstruction). Low renal blood pressure triggers both direct and indirect renal mechanisms to increase blood flow by increasing blood volume. This can cause hypertension (called "secondary hypertension" because it is secondary to a defined cause - in this case the renal obstruction).

How do the lymphatic and cardiovascular systems interact?

The lymphatic system is an open transport system that works in conjunction with the circulatory system. Lymphatic vessels collect intercellular fluid (tissue fluid), kill foreign organisms, and return it to the circulatory system. The lymphatic system can be likened to storm drains. The lymphatic system also prevents tissue fluid from accumulating in the tissue spaces. Lymph capillaries pick up the intercellular fluid, now called lymph, and carry it into larger and larger lymph vessels. Inside the lymph vessels, lymph passes through lymph nodes, where lymphocytes attack viruses and bacteria. The lymphatic system transports lymph to the large brachiocephalic veins below the collarbone where it is re-enters the circulatory system. Lymph moves through the lymphatic system by the squeezing action of nearby muscles, for there is no pump in this system. Lymph vessels are equipped with one-way valves that prevent backflow. The spleen, an organ of the lymphatic system, removes old blood cells, bacteria, and foreign particles from the blood.

Distinguish between the pulmonary and systemic circuits of the cardiovascular system.

The pulmonary circuit of the cardiovascular system consists of those vessels that carry the blood from the heart to the lungs and back to the heart. The systemic circuits of the cardiovascular system are responsible for carrying the blood from the heart to all other parts of the body and back again.

Suppose vasoconstriction decreases the diameter of a vessel to one-third its size. What happens to the rate of flow through that vessel? Calculate the expected size of the change.

The rate of flow will decrease 81-fold from its original flow (3 x 3 x 3 x 3 = 81). Resistance varies inversely with the fourth power of the vessel radius.

Which branch of the autonomic nervous system innervates blood vessels? Which layer of the blood vessel wall do these nerves innervate? What are the effectors (cells that carry out the response)?

The sympathetic nervous system innervates blood vessels. The sympathetic nerves innervate the tunica media. The effector cells in the tunica media are smooth muscle cells.

List three factors that determine resistance in a vessel. which of these factors is physiologically most important?

The three factors that determine blood resistance are blood viscosity, vessel length and vessel diameter. Vessel diameter is physiologically the most important.

List three factors that determine resistance in a vessel. Which of these factors is physiologically most important?

The three factors that determine resistance are blood viscosity, vessel length, and vessel diameter. Vessel diameter is physiologically most important. Because blood viscosity and vessel length are normally unchanging, the influence of these factors can be considered constant in healthy people.

Explain how veins function as blood reservoirs.

The valves prevent a backflow of blood. Their smooth muscle layer is much less developed, allowing more blood to remain in the vein. In times of hemorrhage accompanied by the drop in arterial blood pressure, the muscular walls are stimulated reflexly by sympathetic nerve impulses. The resulting venous constriction pushes out the extra blood, which raises the blood pressure.

2. Will the fracture be attended to, or will Mr. Hutchinson's other homeostatic needs take precedence? Explain your answer choice and predict his surgical treatment.

The vital signs indicate that he is facing a life-threatening problem that must be stabilized before other, less vital problems can be addressed. As for surgery, he may be scheduled for open reduction of his crushed bone, depending upon the condition of the tissues in his crushed right leg. If tissue death has occurred in his let, he may undergo amputation of that limb.

3. What do you conclude regarding Mr. Hutchinson's cardiovascular measurements, and what measures do you expect will be taken to remedy the situation before commencing surgery?

They indicate hypovolemic shock, a type of shock resulting from decreased blood volume. Because his blood volume is low, his heart rate is elevated to increase cardiac output in an effort to maintain the blood supply to his vital organs. His blood volume must be increased as quickly as possible with blood transfusions or IV saline. This will stabilize his condition and allow his physicians to continue with his surgery.

1. Relative to what you have learned about tissue requirements for oxygen, what is the condition of the tissues in the right lower limb?

They were deprived of oxygen and nutrients for at least one-half hour. When tissues are deprived of oxygen, tissue metabolism decreases and eventually ceases, so these tissues may have died due to anoxia.

Describe the control of blood pressure.

Two important mechanisms for blood pressure control involve the regulation of cardiac output and the peripheral resistance. Starling's law of the heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers. Baroreceptors trigger the neural regulation of the heart rate. Chemicals, such as epinephrine, emotions, physical exercise, and increased body temperature can also play a role in regulation of heart rate, thereby influencing the cardiac output. Peripheral resistance is regulated primarily by the changes in the diameters of arterioles. The vasomotor center of the medulla oblongata has neural control of the smooth muscle in the arteriole wall. Chemical substances, including carbon dioxide, oxygen, and hydrogen ions, also influence peripheral resistance by affecting the smooth muscle in the walls of arterioles and the actions of precapillary sphincters.

Describe the control of blood pressure

Two important mechanisms for blood pressure control involve the regulation of cardiac output and the peripheral resistance. Starling's law of the heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers. Baroreceptors trigger the neural regulation of the heart rate. Chemicals, such as epinephrine, emotions, physical exercise, and increased body temperature can also play a role in regulation of heart rate, thereby influencing the cardiac output. Peripheral resistance is regulated primarily by the changes in the diameters of arterioles. The vasomotor center of the medulla oblongata has neural control of the smooth muscle in the arteriole wall. Chemical substances, including carbon dioxide, oxygen, and hydrogen ions, also influence peripheral resistance by affecting the smooth muscle in the walls of arterioles and the actions of precapillary sphincters.

What is the function of venous valves? What forms the valves?

Valves prevent blood from flowing backwards in the veins. They are formed from the folds of the tunica intima.

When vascular smooth muscle contracts, what happens to the diameter of the blood vessel? What is this called?

When vascular smooth muscle contracts, the diameter of the blood vessel becomes smaller. This is called vasoconstriction.

Would your precapillary sphincters be opened or closed if you were doing calf raises at the gym?

Your precapillary sphincters would be open so the true capillaries would be flushed with blood to ensure that the working calf muscles would receive the needed nutrients and dispose of their metabolic wastes.

List the major factors that promote the flow of venous blood.

a. Skeletal muscle contractions b. Respiratory movements c. Venoconstriction

Name several factors that influence the blood pressure, and explain how each produces its effect.

a. The amount of blood that enters the arterial system with each ventricular contraction. This is known as heart action. b. The amount of blood cells and plasma volume in the cardiovascular system, which is known as blood volume. c. The amount of peripheral resistance within the walls of the blood vessels. d. The viscosity (the ease with which molecules in a fluid slide past one another).

Which statement does not accurately describe veins?

always carry deoxygenated blood

Describe veins

have less elastic tissue and smooth muscle than arteries; contain more fibrous tissue than arteries; most veins in the extremities have valves

Peripheral resistance

is inversely related to the diameter of the arterioles

Smooth muscle in the blood vessel wall

is mostly circularly arranged

How is the anatomy of capillaries and capillary beds well suited to their function?

thin walls= maximum delivery of nutrients + O2 beds are connective to provide different routes in case one is damaged Capillary walls are very thin this allows maximal delivery of the nutrients. They have pores for exchange, and are devoid of muscle and connective tissue. (p. 696)

what might an abnormal increase in venous pressure indicate?

venous valve failure

Distinguish between elastic arteries, muscular arteries, and arterioles relative to location, histology, and functional adaptations

•Elastic arteries are the large, thick-walled arteries close to the heart. They have generous amounts of elastic tissue in all tunics, but especially in the tunica media. This elastic tissue enables them to withstand large pressure fluctuations by expanding when the heart contracts, forcing blood into them. They recoil as blood flows forward into the circulation during heart relaxation. They also contain substantial amounts of smooth muscle but are relatively inactive in vasoconstriction. (p. 695) •Muscular arteries are medium-sized, and smaller arteries, farther along in the circulatory pathway, carry blood to specific body organs. Their tunica media contains proportionately more smooth muscle and less elastic tissue than that of elastic arteries, but they typically have an elastic membrane on each face of the tunica media. They are more active in vasoconstriction and are less distensible. (p. 696) •Arterioles are the smallest of the arterial vessels. The smallest—terminal arterioles—feed directly into the capillary beds. The larger arterioles exhibit all three tunics and their tunica media is chiefly smooth muscle with a few scattered elastic fibers. The walls of the smaller arterioles are little more than smooth muscle cells that coil around the tunica intima lining. When arterioles constrict, the tissues served are largely bypassed; when the arterioles dilate, blood flow into the local capillaries increases dramatically. (p. 696)