Module 9

Question 1

Describe the path of blood from entering the heart to re-entering the heart

Answer 1

superior/inferior vena cava -> right atrium -> right AV valve -> right ventricle -> pulmonary semilunar valve -> pulmonary artery -> pulmonary capillaries (lungs) -> pulmonary vein -> left atrium -> left AV valve -> left ventricle -> aortic semilunar valve -> aorta -> arteries -> arterioles -> capillaries -> venules -> veins -> superior/inferior vena cava

Question 2

Name the two distinct circulation loops

Answer 2

pulmonary circulation and systemic circulation

Question 3

Name two smaller loops within systemic circulation

Answer 3

hepatic portal loop (digestive system) and hypothalamic-hypophyseal portal system (in brain)

Question 4

List blood volume distribution throughout the circulatory system

Answer 4

70% veins; 10% arteries; 15% heart and lungs; 5% capillaries

Question 5

Name the vessel type with the highest and lowest blood velocity

Answer 5

highest: arteries; lowest: capillaries

Question 6

Name the vessel type with the highest and lowest blood pressure

Answer 6

highest: arteries; lowest: veins/venules

Question 7

Name the vessel type with the highest and lowest cross-sectional area

Answer 7

highest: capillaries; lowest: arteries

Question 8

Name the area with largest decrease in blood pressure and velocity and why

Answer 8

arteries to arterioles, because of large increase in cross sectional area

Question 9

Explain the relationship between pressure, flow and resistance

Answer 9

flow is calculated by change in pressure divided by resistance (Flow = P1-P2/R); or simplified, Flow = P1-P2 x r^4

Question 10

Explain laminar flow

Answer 10

streamlined flow has less resistance/turbulence, so larger or dilated vessels have less resistance than smaller or constricted vessels, where blood faces more resistance closer to vessel walls

Question 11

Name three factors in resistance to blood flow

Answer 11

thickness/viscosity of blood; length of blood vessel; diameter or radius of blood vessel

Question 12

Explain the equation for resistance and why it can be simplified

Answer 12

R=Ln/r^4, where L is length of blood vessel and n is viscosity, but since both remain constant over short periods of time, R=1/r^4

Question 13

Name two ways to alter blood flow (remember equation)

Answer 13

change pressure gradient; change resistance (aka change radius of blood vessel)

Question 14

Explain Korotkoff’s sounds and how they are used to take blood pressure

Answer 14

tapping sounds produced when flow becomes turbulent as it squeezes through blood vessels pinched off by pressure cuff as pressure releases; systolic pressure is when sounds start and diastolic pressure is when sounds end

Question 15

Explain the structure of an artery

Answer 15

tunica externa (fibrous tissue), media (smooth muscle and elastic tissue), and interna (endothelial cells); lots of elastic tissue to withstand large pressure changes from the heart

Question 16

Explain the structure of an arteriole

Answer 16

mostly smooth muscle to constrict and dilate as needed, and endothelial tissue

Question 17

Explain the structure of a capillary

Answer 17

single layer of endothelial cells to allow diffusion; also has clefts and fenestrations, holes allowing movement of water

Question 18

Explain the structure of a venule

Answer 18

no smooth muscle or elastic tissue, just fibrous tissue and endothelial layer

Question 19

Explain the structure of a vein

Answer 19

tunica externa (fibrous tissue), media (smooth muscle and elastic tissue), and interna (endothelial cells); thinner than arteries, very little elastic tissue, more flexible

Question 20

Name the four Starling Forces and which contribute to filtration and reabsorption

Answer 20

two hydrostatic pressures: capillary (Pc, filtration) and interstitial-fluid (Pif, reabsorption); two osmotic forces: due to plasma protein concentration (πp, reabsorption) and due to interstitial-fluid protein concentration (πif, filtration)

Question 21

Explain the capillary hydrostatic pressure

Answer 21

Pc is pressure from fluid forcing outward on the walls of capillaries; contributes to filtration; is different at arterial and venous end of capillary

Question 22

Explain the interstitial-fluid hydrostatic pressure

Answer 22

Pif is pressure from fluid pushing back on capillary; contributes to reabsorption (unless negative, then to filtration); generally zero unless otherwise specified; varies from organ to organ

Question 23

Explain the osmotic force of plasma

Answer 23

πp draws fluid into capillary, contributing to reabsorption; since plasma has lots of proteins, force is generally high

Question 24

Explain the osmotic force of proteins in the interstitial space

Answer 24

πif pulls fluid out of capillary, causing filtration; since interstitial fluid has little proteins, force is low

Question 25

Describe the equation for net filtration pressure and overall net filtration

Answer 25

NFP = (Pc-Pif) - (πp-πif); calculated at arterial and venous end where Pc will differ, positive means filtration and negative means reabsorption; overall net filtration is adding them together

Question 26

Describe how the lymphatic system works

Answer 26

small blind-ended capillaries absorb excess fluid; transport to larger collecting vessels that filter through lymph nodes then send fluid back to venous circulation

Question 27

List factors contributing to edema

Answer 27

increase in Pc caused by increased blood pressure; decreased πp due to malnutrition; blockage or disruption of lymphatic system

Question 28

Define autoregulation

Answer 28

the process by which individual capillary beds maintain relatively constant blood flow when moderate changes occur in blood pressure

Question 29

Explain the myogenic theory

Answer 29

sudden increase in blood pressure to vital organ will cause vessels to dilate, so a reflex to contract smooth muscle in walls of arteriole supplying the organ will cause vasoconstriction to decrease blood pressure/flow and prevent damage to capillary network; opposite can happen

Question 30

Explain the metabolic theory

Answer 30

changing metabolic activity will change blood flow to that organ; cardiovascular system will respond to increase in heat, CO2, lactic acid, and adenosine in muscles, causing vasodilation and increased blood flow to active tissue until metabolites are washed out

Question 31

Explain humoral regulation

Answer 31

regulation of blood flow by chemical substances circulating in the blood other than local metabolites, like hormones; fall into two categories of vasodilators and vasoconstrictors

Question 32

List agents responsible for vasoconstriction

Answer 32

epinephrine (weak effect on intestinal blood vessels); angiotensin ii (ang ii) (most powerful, associated with renal system); vasopressin (aka ADH) (also associated with renal system)

Question 33

List agents responsible for vasodilation

Answer 33

epinephrine (in skeletal muscle and cardiac muscle); kinins (hormones formed in plasma and tissue); histamine (released from damaged cells); atrial natriuretic factor (ANF) (produced by atrial muscle cells)

Question 34

Explain the equation for blood pressure, or mean arterial pressure

Answer 34

MAP = cardiac output (CO) x total peripheral resistance (TPR); increasing either will increase blood pressure; TPR is sum of all resistance in all blood vessels in the body

Question 35

Briefly explain the baroreceptor reflex

Answer 35

negative feedback mechanism; special stretch receptors in walls of aortic arch and carotid sinuses detect increased blood pressure/stretching, send signals to cardioregulatory and vasomotor centers in medulla oblongata, send signals back through PSYN to decrease heart rate, send signals through SYN to dilate vessels and decrease blood pressure