Microcirculation

Question 1

The exchange of gases across the capillary wall occurs via

Answer 1

diffusion

Question 2

Lipid soluble gases

Answer 2

O2, CO2. diffuse THROUGH endothelial cells

Question 3

Water, glucose, amino acids

Answer 3

are not lipid soluble gases; cannot pass through endothelial cells via diffusion

must pass through aqueous clefts between endothelial cells, so limited by surface area

Question 4

hydrostatic and osmotic pressure

Answer 4

sterling forces

Question 5

Simple diffusion is driven by

Answer 5

partial pressure gradients of the individual gases.

Question 6

Rate of simple diffusion is determined by

Answer 6

partial pressure of gases and the surface area available for diffusion

Question 7

in capillaries the driving force across the endothelia include

Answer 7

hydrostatic and osmotic forces

Question 8

Sterline equation =

Answer 8

Fluid =
(Cap Hyd presh - Interstish hydrostatic presh) - (capillary oncotic presh - interstitial oncotic presh)

tells you what direction the movement of fluid will go

it’s always (C-I)-(C-I)

Question 9

fluid OUT of the capillary is called

Answer 9

filtration

Question 10

fluid INTO the capitally is called

Answer 10

absorption

Question 11

Sterling equation constant is what?

Answer 11

K, the magnitude of fluid movement. it is a hydrolytic conductance (Water permeability)

Question 12

a + sterling value indicates ___ and a - sterling value indicates

Answer 12

filtration and absorption

Question 13

hydraulic conductance is not influenced by things such as

Answer 13

hypoxia, metabolites, arteriolar resistance

Question 14

hydraulic conductance IS influenced by

Answer 14

capillary injury

Question 15

Capillary hydrostatic pressure

Answer 15

determined by venous and arterial pressures
closer to arterial pressure
influenced by changes in venous pressure more than arterial pressure

Question 16

what happens to interstitial fluid that leaves the capillaries?

Answer 16

it has to be returned to the capillaries or removed by the lymphatic system

Question 17

what can alter capillary hydrostatic pressure?

Answer 17

enema
elevated by venous pressure during heart failure
influenced by a decrease in albumin (starvation and liver failure)

Question 18

what can alter interstitial hydrostatic pressure?

Answer 18

edema
can be restricted by lymphatic flow or increased driving out of capillary

can be restricted by lymph flow or inflammation

Question 19

Interstitial capillary pressure is usually

Answer 19

0 or a little bit negative

Question 20

What two big things generally favor filtration?

Answer 20

decreased capillary oncotic pressure and increased venous pressure

Question 21

edema: definition

Answer 21

forms when volume of interstitial fluid, due to filtration out of the capillaries) exceeds the ability of lymphatics to return it to circulation

Question 22

Autoregulation: which organs exhibit autoregulation and what is it

Answer 22

maintenance of a constant blood flow. certain organs have intrinsic mechanisms that attempt to maintain the blood flow to meet their metabolic needs under changing conditions

kidneys
brain
heart
skeletal muscle

Question 23

blood flow to an organ or tissue is proportional to its _____
and this is described by

Answer 23

metabolic requirements

active hyperemia—> the flow of blood to tissues based on their needs

Question 24

reactive hyperemia

Answer 24

increase in blood flow in response to or reacting to a prior period of decreased blood flow.

so let’s say there was a period of arterial occlusion, reactive hyperemia would be the response afterwards

Question 25

Myogenic hypothesis

Answer 25

can be invoked to explained autoregulation but doesnt explain hypermia (either forms)

this hypothesis states that when smooth muscle is stretched, it causes contraction

Question 26

Law of laplace for a cylinder

Answer 26

T = P x r

T = wall tension 
P = pressure 
r = radius 

this formula explains the myogenic hypothesis. tension decreases when R or P decrease etc.

Question 27

metabolic hypothesis

Answer 27

can be invoked to explain each of the phenomena of local control of blood flow

basic premise of this theory is that O2 delivery = O2 consumption by tissue by altering alterial resistance, which in turns alters blood flow

Question 28

metabolic hypothesis: what is the ultimate result?

Answer 28

the theory is that metabolic activity causes the production of “vasodilator metabolites” like CO2, H, K, lactate, and adenosine

these cause vasodilation which allows increased blood flow, allowing delivery of O2

Question 29

vasodilator metabolites

Answer 29

produced by metabolically active tissues: include CO2, lactate, adenosine, H, K, which cause vasodilation, allowing more blood to come and supply more O2

Question 30

which theory is best described by the metabolic hypothesis?

Answer 30

active hyperemia

Question 31

describe how the metabolic hypothesis best describes active hyperemia

Answer 31

strenuous exercise: as skeletal muscle undergoes rapid cross cycling, the tissues required to meet the energy requirements are producing metabolites like lactate: these cause increased vasodilation, allowing delivery of more blood and thus O2 for electron capture

Question 32

Extrinsic control of regional blood flow is by

Answer 32

neural control, specifically sympathetic (I think)

Question 33

histamine and its relation to hydrostatic pressure

Answer 33

vasoactive substance

released in response to trauma, causes arterial vasodilation and venous vasoconstriction

net effect: LARGE increase in capillary hydrostatic pressure

increases Kf

Question 34

bradykinin

Answer 34

like histamine, causes arterial vasodilation and venous vasoconstriction
localized edema

‘arteriolar vasodilation’

increases Kf

Question 35

serotonin

Answer 35

released in response to blood vessel damage and causes local vasoconstriction (in an attempt to reduce blood flow and blood loss)

Question 36

Shear force in capillary beds

Answer 36

if vascular bed dilates in response to metabolic need, increased blood flow through arteries causes shearing–or friction–against vessel walls, compelling them to release NO to induce relaxation which would allow them to augment the downstream metabolic effect

Question 37

Prostaglandins

Answer 37

prostacyclins - relaxation

thromboxane - constriction

Question 38

Angiotensin II and vasopressin

Answer 38

vasoconstrictors that increase TPR

Question 39

what is the parasympathetic control of vasculature entail?

Answer 39

there are no parasympathetics

Question 40

Coronary circulation: main types of control

Answer 40

almost entirely metabolic, sympathetics are limited

Question 41

Two most important metabolic factors for coronary flow include

Answer 41

hypoxia and adenosine

Question 42

Cerebral circulation control factors

Answer 42

controlled almost entirely by local metabolites
exhibits autoregulation and active and reactive hyperemia

most important regulator is CO2 (or H, same thing)

an increase in PCO2 causes an increase in H, therefore a decrease in pH and a