Arteries, Veins, and Microcirculation

Question 1

WHat vessels have the highest wall thickness to lumen diameter?

Answer 1

precapillary spincters

arterioles are close

Question 2

elastic modulus

Answer 2

force per unit area that is required to stretch a material to 2x its original length or the slope of the stress/strain relationship to the right

Question 3

What happens to arterial compliance with age?

Answer 3

decreases with age

less elastin and mroe collagen

Question 4

Windkessel effect

Answer 4

the walls of the aorta act as a secondary pump by stretching out during systole and then continuing to pump blood during diastole

this effect wears off with age

Question 5

Laplace’s law

Answer 5

the pressure inside a cylindrical or spherical vessel exerts a distending force on the wall proportional to the magnitude of the pressure and the radius

T = (P_i - P_t)/h

P_i = intravascular pressure

P_t = tissue pressure

Question 6

pulse pressure

Answer 6

systolic pressure - diastolic pressure

Question 7

physical factors that affect arterial blood pressure

Answer 7

arterial blood volume and compliance

Question 8

factors affecting diastolic presssure

Answer 8

resistance - run off rate

compliance of the aorta

systolic pressure

heart rate

Question 9

mean arterial pressure equation

Answer 9

MAP = CO x TPR

Question 10

runoff

Answer 10

blood flowing away from the heart to the peripheral arteries and tissues

the greater the runoff, the lower the pressure

Question 11

What is the relationshi between wave frequency of blood flow and dampening?

Answer 11

low frequency waves move more slowly but undergo less dampening

high frequency waves move faster but undergo more dampening

Question 12

What does decreasing distensibility do to rate of flow and dampening?

Answer 12

it increases rate of flow and causes more dampening

Question 13

metarterioles

Answer 13

discontinuous single layer of vascular smooth muscle cells generally not innervated

Question 14

characteristics of blood flow through capillaries

Answer 14

low velocity

intermittent due to vasomotion

changes direction due to pressure gradients

not uniform

Roleaux formation

Question 15

Roleaux formation

Answer 15

“stack of coints” arrangement of RBCs

Question 16

vasomotion

Answer 16

spontaneous contraction and relaxation of precapillary sphincters

increased metabolic activity increases the time that precapillary sphincters are open

decreased oxygen delivery has the same effect

Question 17

capillary hydrostatic pressure (Pc)

Answer 17

major determinant of fluid movement

determined by arterial pressure, venous pressure, and the ratio of venular to arteriolar resistance

Pc = [(Rv/Ra)*Pa + Pv]/[1 + (Rv/Ra)]

Question 18

How does increasing pre/post pressure affect capillary hydrostatic pressure?

Answer 18

decrease

Question 19

How does decreasing pre/post pressure affect capillary hydrostatic pressure?

Answer 19

increased

Question 20

interstitial hydrostatic pressure

Answer 20

changes only slightly except in cases of lymphatic blockage or increased capillary permeability

normally around -1 mmHg

Question 21

osmotic pressure

Answer 21

favors absorption

about 25 mmHg for water to enter the capillary due to the higher concentration of plasma proteins

pi = sRT (C_I - C_O)

Question 22

What protein contributes the most of the plasma oncotic pressure

Answer 22

albumin - 51%

disproportionately large based on concentration

Question 23

Starling’s Law for capillary fluid movement

Answer 23

fluid movement = k[(Pc + pi_i) - (Pi + pi_p)]

normally the first half fluid leaves (20L) and the second half is reabsorption of water (18L)

the remainder draings through the lymphatics

Question 24

lymph

Answer 24

fluid and other plasma proteins that accumulate in the extravascular space

composition similar to plasma

flow depends on interstitial hydrostatic pressure

Question 25

factors that predispose one to edema

Answer 25

increased capillary pressure

increased capillary permeability

decreased plasma protein concentration

excessive protein excretion, excess salt and fluid retention

lymphatic blockage