Blood Vessels & Hemodynamics - Topic Outline & Objectives 2021-09-13 05 02 55 PDF

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Blood vessels and hemodynamics - The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The haemodynamic response continuously monitors and adjusts to conditions in the body and its environment...

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Blood Vessels and Hemodynamics TOPIC OUTLINE AND OBJECTIVES A. Structure and function of blood vessels; capillary exchange 1. Contrast the structure and function of arteries, arterioles, capillaries, venules, and veins. 2. Outline the vessels through which the blood moves in its passage from the heart to the capillaries and back. 3. Distinguish between pressure reservoirs and blood reservoirs. 4. Discuss the pressures that cause movement of fluids between capillaries and interstitial spaces. B. Hemodynamics: factors affecting blood flow and blood pressure 1. Explain the factors that regulate the volume of blood flow. 2. Explain how blood pressure changes throughout the cardiovascular system. 3. Describe the factors that determine mean arterial blood pressure and systemic vascular resistance. 4. Describe the relationship between cross-sectional area and velocity of blood flow. 5. Describe how blood pressure is regulated. C. Checking circulation; shock and homeostasis 1. Define pulse, and define systolic, diastolic, and pulse pressure. 2. Define shock, and describe the four types of shock. 3. Explain how the body's response to shock is regulated by negative feedback. D. Circulatory routes: systemic arteries 1. Describe and compare the major routes that blood takes through various regions of the body. 2. Identify the four principal divisions of the aorta. 3. Locate the major arterial branches arising from each division. 4. Identify the two primary arterial branches of the ascending aorta. 5. Identify the three principal arteries that branch from the arch of the aorta. 6. Identify the visceral and parietal branches of the thoracic aorta. 7. Identify the visceral and parietal branches of the abdominal aorta. 8. Identify the two major branches of the common iliac arteries. E. Circulatory routes: systemic veins 1. Identify the three systemic veins that return deoxygenated blood to the heart. 2. Identify the three major veins that drain blood from the head. 3. Identify the principal veins that drain the upper limbs. 4. Identify the components of the azygos system of veins. 5. Identify the principal veins that drain the abdomen and the pelvis. 6. Identify the principal superficial and deep veins that drain the lower limbs. F. Circulatory routes: hepatic portal, pulmonary, and fetal circulation G. Aging of the cardiovascular system 1. Explain the effects of aging on the cardiovascular system. H. Disorders, medical terminology A. Structure and function of blood vessels; capillary exchange Check your understanding of the structure of blood vessels by matching terms with their descriptions. VV. Vasa vasorum

TE. Tunica externa

TM. Tunica media

TI. Tunica interna (intima)

L. Lumen

_____ a. The opening in blood vessels through which blood flows; narrows in atherosclerosis _____ b. Tiny blood vessels that carry nutrients to walls of blood vessels _____ c. Formed largely of endothelium and basement membrane, it lines lumen; the only layer in capillaries _____ d. Composed of muscle and elastic tissue; contraction permits vasoconstriction _____ e. Strong outer layer composed mainly of elastic and collagenous fibers

Match the names of vessels with the descriptions below. Answers may be used once, more than once, or not at all. Inferior vena cava

Arterioles

Elastic arteries

Muscular arteries

Small veins

Capillaries

Venules

a. Known as exchange vessels, they are sites of gas, nutrient, and waste exchange with tissues ____________________. b. Known as resistance vessels, they play the primary role in regulating moment-to-moment distribution of blood and therefore in regulating blood pressure: ____________________. c. Sinusoids of liver are wider, more leaky versions of this type of vessel: ____________________. d. Reservoirs for about 60% of the volume of blood in the body; vasoconstriction (due to sympathetic impulses) permits redistribution of blood stored here (three answers): ____________________, .____________________., ____________________. e. Largest-diameter arteries such as aorta, common carotids, and pulmonary arteries; have thick, elastic tunica media that allows these vessels to expand and serve as pressure reservoirs; also known as conducting arteries: ____________________. f. Vessels with thick, muscular tunica media; largest of these vessels (such as femoral arteries) have pencil-sized diameter; also known as distributing arteries: ____________________. g. Flow of blood through here is called microcirculation: ____________________. Locate illustrations of the types of capillaries in your textbook, and identify the structural features of the capillaries and sinusoids that permit passage of materials across the vessel wall by these four different routes listed below. Fenestrations

Intercellular clefts

Pinocytic vesicles

Direct movement across endothelial membranes a. Structural features of very thin endothelial membrane with thin, incomplete, or even absent basement membrane, for example, in sinusoids: ____________________. b. Gaps known as ______________________________________ between neighboring endothelial cells that lack a basement membrane; may be large, for example, to permit passage of large proteins made in liver cells into the blood in liver sinusoids. c. Pores known as ______________________________________ in plasma membranes of endothelial cells, for example, in cells of kidneys, intestinal villi, ciliary processes of the eye and choroid plexuses of the brain. The tight seal of the blood-brain barrier is attributed partly to lack of such pores. d. ______________________________________ permitting endocytosis and exocytosis for transport of large molecules that cannot cross capillary walls in any other way Complete this activity about the structure of veins. a. Veins have (thicker? thinner?) walls than arteries. This structural feature relates to the fact that the pressure in veins is (more? less?) than in arteries. The pressure difference is demonstrated when a vein is cut; blood leaves a cut vein in (rapid spurts? an even flow?). b. Gravity exerts back pressure on blood in veins located inferior to the heart. To counteract this, veins contain________________ c. When valves weaken, veins become enlarged and twisted. This condition is called ______________________________________ This occurs more often in (superficial? deep?) veins. Why?

d. Identify two locations in the gastrointestinal tract where varicosities are relatively common. 1. 2. e. A vascular (venous) sinus has ________________________________ replacing the tunica media and tunica externa. So sinuses have the (structure but not function? function but not structure?) of veins. List two places where such sinuses are found. 1. 2. Complete this activity on the distribution of blood. a. At rest, (arteries and arterioles? capillaries? venules and veins?) contain most of the blood in the body, specifically, about ______% of blood in the human body. In which vessels is the smallest percentage of blood found in the resting person? (Arteries and arterioles? Capillaries? Venules and veins?) This volume of blood makes up about _____ % of circulating blood. b. (Sympathetic? Parasympathetic?) nerve impulses to venules and veins cause vasoconstriction and release of blood from these vessels. Name two locations of venous "reservoirs" that can be activated to release blood when needed. 1. 2. c. State two or more examples of circumstances that might activate distribution of reservoir blood. 1. 2. Identify the types of transport mechanisms involved in capillary exchange. B. Bulk flow

S. Simple Diffusion

T. Transcytosis

_____ a. Passage of lipid-soluble chemicals, such as oxygen, carbon dioxide, and steroid hormones, through the phospholipid bilayer of capillary membrane endothelial cells _____ b. Movement of antibody proteins from maternal blood to fetal blood _____ c. Transport of water-soluble substances, such as glucose or amino acids, through fenestrations or intercellular clefts _____ d. Passive movements of large numbers of ions, molecules, and particles in the same direction, largely due to opposing forces of blood pressure and osmotic pressure _____ e. Movement of large plasma proteins, such as fibrinogen or albumin, made in liver cells through intercellular clefts in sinusoids to reach plasma Locate an illustration of the four pressures involved in capillary exchange in your textbook and identify the four pressures involved in capillary exchange. a. These pressures interact in way that results in a net filtration pressure (NFP) of _________ mm Hg. In other words, at the arterial end of the capillary, substances tend to move (into? out of?) the capillary. b. Which value is substantially different at the venous end of capillaries? ______________ Calculate the NFP at the venous end: NFP = (BHP+ IFOP) – (BCOP + IFHP) = ______________ mm Hg

c. The near-equilibrium at the two ends of capillaries is based on __________________________________'s law of the capillaries. Which system reabsorbs the little amount of fluid that is not drawn back into veins? __________________________________ d. Excessive amounts of fluid accumulating in interstitial spaces is the condition known as _______________________. This may result from high blood pressure in which (BCOP? BHP?) is increased, loss of plasma protein in which (BCOP? BHP?) is decreased, or (increase? decrease?) in capillary permeability. Three patients were noted as having edema. Identify the physiological cause that was most likely responsible for each case of edema. Select from the answers below:

BHP. Increased blood hydrostatic pressure (blood pressure) PC. Increased permeability of capillaries  ECV. Increased extracellular volume  PP. Decreased concentration of plasma proteins _____ a. A 70 y/o male has a diagnosis of congestive heart failure and experiences shortness of breath. _____ b. A 9 y/o male with second-degree burns on his lower extremity with swelling and seeping fluids _____ _____ c. A 40 y/o. female with kidney failure has gained 11 pounds since her last hemodialysis treatment 3 days ago. She admits to overeating and drinking over the weekend (Two answers)

B. Hemodynamics: factors affecting circulation and blood pressure. Check your understanding of circulation of blood. a. The typical human body contains about liters of blood. At rest, this same amount of blood is pumped out by the heart each minute, as cardiac ____________ (about 5 liters/minute). b. Name the two factors that determine how rapidly and where this blood is distributed, for example, rapid delivery to brain and muscles, or slow delivery to intestine and skin. 1. 2.

Complete this activity on blood pressure (BP) and mean arterial blood pressure (MABP). a. In the aorta and brachial artery, blood pressure (BP) is normally about 110 mm Hg immediately following ventricular contraction. This is called (systolic? diastolic?) BP. As ventricles relax (or go into _______________ ), blood is no longer ejected into these arteries. However, the normally (elastic? rigid?) walls of these vessels recoil against blood, pressing it onward with a diastolic BP of ______mm Hg. b. In a blood pressure (BP) of 120/80, the average of the two pressures (systolic and diastolic) is 100. However the MABP (average or mean blood pressure in arteries) for a BP of 120/80 is actually slightly less than 100; it is about _________ . Reason: during the typical cardiac cycle (0.8 sec), the ventricles are in (systole? diastole?) for about two-thirds of the cycle and in systole for only about one-third of the cycle. As a result, the MABP is always slightly closer to the value of the (systolic? diastolic?) BP. c. Try calculating MABP for a person with an arterial BP of 120/78. First write the diastolic BP,__________ mm Hg. Then find the difference between systolic BP and diastolic BP a value known as pulse pressure: 120 mm Hg - 78 mm Hg =__________ mm Hg. Finally, add one-third of pulse pressure to diastolic BP to arrive at MABP: BP diastolic+ ( 1/3 x pulse pressure)= MABP or _______ mm Hg + ( 1/3 x ______mm Hg) = _________mm Hg

Earlier you named two factors that determine distribution (or circulation) of cardiac output to the body. a. One factor is __________________________ (such as blood pressure or MABP). Define blood pressure: the pressure exerted by_________________________________________________. If cardiac output (CO) increases, BP or MABP are likely to (increase? decrease?), Finish the arrow to show the correct relationship:  CO  MABP. On the other hand, if CO decreases (as in hemorrhage or shock), then MABP is likely to (increase? decrease?). b. Now visualize the effects of the second factor (resistance) on distribution of blood. Blood moves at high velocity through the aorta or other large arteries. BP is high there (MABP of 92) as blood flows along freely. As blood enters a small artery or arteriole, a RBC encounters (more? less?) resistance to flow as the RBC repeatedly bounces up against walls of this narrow-diameter vessel. In other words, BP in any given blood vessel is (directly? inversely?) related to resistance to flow, while (directly? inversely?) related to cardiac output. In fact, as the diameter of a vessel is halved, resistance to flow through that vessel (increases? decreases?) to (2? 4? 8? 16?)-fold. c. Because CO stays the same within the body at any given time, we can conclude that if resistance to flow is high through a vessel (such as an arteriole or capillary), that BP in that vessel will be (high? low?). Referring to the figure below, write the normal ranges of BP values for the following types of vessels: arterioles ____________ mm Hg; capillaries ____________ mm Hg; venules and veins ____________ mm Hg; venae cavae ____________ mm Hg.

d. On the figure the steepest decline in the pressure curve occurs as blood passes through the (aorta? arterioles? capillaries?). This indicates that the greatest resistance to flow is present in the (aorta? arterioles? capillaries?) . Do this exercise on two very important and different relationships between resistance (R) and blood pressure (BP). a. An increase in resistance (R) within a given blood vessel causes (increase? decrease?) in BP in that vessel. Therefore, BP (within a vessel) and R (in that same vessel) are inversely related. Show this by completing the arrow.

R within a vessel  | BPin that same vessel For example, a RBC passing from an artery into an arteriole meets more resistance to flow in this narrow vessel, thereby (increasing? decreasing?) BP within that vessel. So the increased resistance (R) blood meets as it passes through arterioles causes BP there to decrease from about 85 to 35 mm Hg. b. However, several factors contribute to changes in BP in systemic arteries (usually measured in the brachia! artery), for example, increase in BP from a normal ______/_____ mm Hg to a high BP of 162/98 mm Hg. One of these factors altering systemic BP is resistance. But here the resistance refers to inhibition of flow through many, many small systemic vessels, for example, by sympathetic nerve stimulation of arterioles causing them to narrow. So the term SVR (vascular _________ ) is used to describe this resistance. Because less blood is engaged in flow into arterioles, more blood stays in main arteries, thereby increasing systemic BP. Complete arrows to show this:

 R within systemic arterioles, as in skin or abdomen  | BPin systemic arteries or  SVR  | BP systemic arteries

Consider this analogy: if blood (water) cannot pass from an artery (wide river) into many arterioles (tributaries) because entranceways are blocked by vasoconstriction of arterioles (tributaries are dammed with debris), then blood (water) will remain in the main artery (wide river), (increasing? decreasing?) BP in main systemic arteries (wide rivers). c. Systemic BP tends to increase if either cardiac output or systemic vascular resistance (SVR) or both of those factors increase. Show this by completing the equation: BP systemic arterial = __________________ x ____________________ or MABP = cardiac output x systemic vascular resistance d. Describe three factors that may increase SVR leading to increased systemic BP: 1. _____-crease in blood viscosity, for example, due to ____________________________ 2. _____-crease in total length of blood vessels in the body, for example, due to 3. _____-crease in diameter (or radius) of blood vessels, for example, by ____________________ of arterioles e. SVR is also called total resistance (TPR) because the vessels that are targeted to vasoconstrict (decrease radius) and create that resistance are those in regions of the body (such as skin and ____________________________that could be considered more "peripheral," or less crucial, to survival. Joe Sixpack has been depressed since his girlfriend left him two years ago and has gained 50 pounds during that time. a. Which one of the following factors that increase systemic vascular resistance is most likely to be higher in Joe? A. Blood viscosity B. Blood vessel length C. Blood vessel radius This factor (does? does not?) puts Joe at higher risk for hypertension. b. Because Joe's stress level is often high, his (sympathetic? parasympathetic?) nerves are likely to be more active. Which of the three factors (A-C) above is most likely to be affected? (A? B? C?) If his arterioles decrease in diameter by 50%, the resistance to flow increases ______________ times. This factor is likely to (increase? decrease?) his blood pressure. Explain how these two factors increase venous return during exercise. a. Skeletal muscle pump

b. Respiratory pump

Do this exercise about blood flow. This figure shows that velocity of blood flow is greatest in (arteries? capillaries? veins?). Flow is slowest in _____________________. As a result, ample time is available for exchange between capillary blood and tissues. b. As blood moves from capillaries into venules and veins, its velocity (increases? decreases?), enhancing venous return. c. Although each individual capillary has a cross-sectional area which is microscopic, the body contains so many capillaries that their

total cross-sectional area is enormous. All of the capillaries in the body have a total cross-sectional area of about _____________cm2. d. (A direct? An indirect?) relationship exists between cross-sectional area and velocity of blood flow. This is evident in the aorta also. This vessel has a cross section of only about _____________cm2 and has a very (high? low?) velocity. e. Mr. Jack Daniels has an aortic aneurysm. The diameter of his aorta has increased from normal size to about 10 cm. The region of the aorta with the aneurysm therefore has a (larger? smaller?) cross-sectional area. One would expect the velocity of Mr. Daniel's aortic blood flow to (increase? decrease?). This change may put Mr. Daniels at risk for______________________________. f. On the average, (1? 5? 10?) minute(s) is normally required for a blood cell to travel one complete circulatory circuit, for example, heart lung  heart  hand  heart. g. Inadequate blood flow to the brain is one cause of fainting, clinically known as ______________________________. List several causes of this condition.

Fill in blanks and complete arrows to show details of all of the nervous output, hormonal action, and other factors that increase blood pressure.

Complete this exercise about blood pressure disorders.

a. Hypertension means (high? low?) blood pressure. It may be caused by an excess of any of the factors shown in the figure on the previous page. If directions of arrows in the figure are reversed, blood pressure can be (increased? decreased?). b. Circle all the factors listed below that tend to decrease blood pressure. A. Increase in cardiac output, as by increased heart rate or stroke volume B. Increase in (vagal) impulses from cardio-inhibitory center C. Decrease in blood volume, as following hemorrhage D. Increase in blood volume, by excess salt intake and wa...