Circulation Overview and Hemodynamics

Question 1

function of the pulmonary circulation

Answer 1

oxygenation of de-oxygenated blood

Question 2

What side of the heart pumps oxygenated blood? Deoxygenated?

Answer 2

Left = oxygenated 
Right = deoxygenated

Question 3

Breakdown of the blood volume in the systemic circulation:

Answer 3

75% veins
20% arteries
5% capillaries

Question 4

benefit of parallel vascular beds during strenuous exercise

Answer 4

organ systems can act independently and can regulate blood flow according to their needs

Question 5

Three examples of series-coupled vascular circuits:

Answer 5

GI tract –> liver: ensures rapid and indicated delivery of absorbed nutrients to the liver for processing

Kidney (glomerular –> peritubular): maintains balance between fluid/nutrient filtration and reabsorption

Hyothalamus –> anterior pituitary: ensures rapid transport of hormones (ex: TRH –> TSH –> thyroxine)

Question 6

structure of arteries

Answer 6

lots of elastin

Question 7

structure of arterioles

Answer 7

lots of smooth muscle

Question 8

structure of capillaries

Answer 8

only endothelial lining

Question 9

structure of venules

Answer 9

endothelium and a little collagen (fibrous tissue)

Question 10

structure of veins

Answer 10

little elastin, smooth muscle, and collagen

Question 11

diameter of the aorta

Answer 11

2-3 cm

Question 12

passageway from the heart to the organs; serves as a pressure reservoir

Answer 12

arteries

Question 13

primary resistance vessels; determines distribution of CO

Answer 13

arterioles

Question 14

site of exchange; determine distribution of extracellular fluid between plasma and interstitial fluid

Answer 14

capillaries

Question 15

passageway to the heart from the organs; serve as a blood reservoir

Answer 15

veins

Question 16

Why are arteries considered a pressure reservoir?

Answer 16

• a fraction of SV is stored in arteries during systole due to stretching
• during diastole, the stretched vessel recoils and displaced blood volume ensures continuous capillary flow

Question 17

major site of blood flow regulation (contract and relax to regulate flow)

Answer 17

arterioles

Question 18

In capillaries, what is exchanged at intercellular junctions (clefts)?

Answer 18

1. ) diffusion of H2O, glucose

2. ) retention of plasma proteins

Question 19

Why are veins considered to be blood reservoirs?

Answer 19

veins are distensible and can accommodate large volumes of blood without elastic recoil

Question 20

most of the resting blood volume resides here

Answer 20

veins and venules

Question 21

branch of physiology that deals with the flow of blood in the circulation

Answer 21

hemodynamics

Question 22

Hemodynamics is based on the physics of two things:

Answer 22

homogenous fluid flow through rigid tubes (this is not true of vessels!! blood vessels are compliant and contain a heterogenous fluid)

Question 23

percentage of blood that in RBC

Answer 23

hematocrit

Question 24

depressed hematocrit

Answer 24

anemia

Question 25

elevated hematocrit

Answer 25

polycythemia

Question 26

How does hematocrit determine our blood viscosity?

Answer 26

Polycythemia = increased Hct

Question 27

formula for velocity of blood flow through vessels

Answer 27

volume / cross sectional area *velocity is inversely related to cross-sectional area

Question 28

Describe laminar flow.

Answer 28

- the fluid particles move in lamina (sheets) - fluid in different lamina move in parallel (slide along each other) - velocity of fluid increases toward the center due to sliding

Question 29

maximum velocity in the center of laminar flow

Answer 29

parabolic velocity profile

Question 30

laminar vs turbulent flow

Answer 30

Laminar flow: - normal pattern of flow in vasculature - highly efficient - follows the Poiseuille law Turbulent flow: - occurs in regions where flow velocity is high - inefficient, chaotic movement - cannot apply the Poiseuille law

Question 31

Reynold's number

Answer 31

Re low = laminar flow | Re high = turbulent flow

Question 32

turbulent flow causes these audible vibrations

Answer 32

eddy currents

Question 33

How does blood velocity and viscosity affect Reynold's number?

Answer 33

Increased blood velocity = heart chambers, valves, and adjacent vessels have a narrowed lumen (atherosclerotic plaques) Decreased blood viscosity = decreased Hct (anemia)

Question 34

When can you hear a murmur when listening to the carotid artery?

Answer 34

turbulence caused by an atherosclerotic plaque

Question 35

another word for a murmur in a vessel

Answer 35

bruit

Question 36

relationship between pressure, flow, and resistance

Answer 36

flow = pressure gradient / resistance

Question 37

Poiseuille's law: determinants of flow

Answer 37

F α r^4 doubling the radius increases flow 16-fold F α 1/l increasing the length will decrease blood flow proportionately F α 1/n increasing the viscosity will decreases blood flow proportionately

Question 38

In the cardiovascular system (according to Poiseuille's law), resistance to flow is determined primarily by _______.

Answer 38

vessel radius

Question 39

major site of resistance to blood flow

Answer 39

arterioles

Question 40

highest resistance

Answer 40

capillary

Question 41

As radius increases, resistance ________. As radius decreases, resistance ________.

Answer 41

decreases / increases

Question 42

Why are the arterioles the major resistance vessels rather than the capillaries?

Answer 42

the number of vessels in parallel (capillaries >>> arterioles)

Question 43

Resistances in series vs in parallel

Answer 43

In series: - R total = R1 + R2 + R3 - R total is greater than the highest individual resistance In parallel: - 1/R total = 1/R1 + 1/R2 + 1/R3 - R total is less than the resistance of any of the individual tubes - adding additional tubes (regardless of their resistance) decreases R total

Question 44

Law of Laplace

Answer 44

T = PR - at any internal pressure (P), wall tension (T) is directly proportional to the radius R - increase in radius results in higher tension - small radius of capillaries allows them to withstand very high pressures without rupturing

Question 45

What is an aneurysm?

Answer 45

weakening of the arterial wall (destruction of the elastin/collagen layer) --> will lead to the rupturing of the vessel if left untreated

Question 46

vicious cycle of an aneurysm

Answer 46

artery wall develops a weak spot --> wall expands --> wall is subject to more tension -->

Question 47

causes of aneurysms:

Answer 47

hypertension local vessel injury congenital abnormality aging