Capillary Permeability Flashcards
capillary wall is composed of a
single layer of endothelial cells
what are two reasons for the efficient exchange of gases/nutrients in capillaries?
- Blood velocity is very slow: “sluggish” gives adequate time for exchange across the capillary membrane
- Huge surface area: over 10 million capillaries
Capillary permeability:
fastest blood velocity?
slowest blood velocity?
fastest: aorta
slowest: capillaries
Capillary permeability:
velocity is ______ proportional to the ______ ____
velocity is inversely proportional to cumulative area
velocity of blood flow =
V = F/A
V=velocity
F=flow rate
A=cross-sectional area of vessels
*velocity is inversely proportional to the cumulative area
hydrostatic pressure:
the force per unit area exerted on the wall of a blood vessel by the blood moving through it
slower flow promotes _______ & _______
greater gas and nutrient exchange
low pressure protects capillaries from ________
rupture
normal capillary BP is ______
low
*protects capillaries from rupture and promotes exchange
BP ______ as blood flow leaves the capillaries
lowers
hydrostatic pressure ____ as you move from the aorta to arteries then to arterioles, and so on…
decreases
at any time on ____% of circulating blood is in the capillaries
~5%
what percent of blood is considered the most important portion of blood volume and where is it located?
~5% in capillaries
where does O2 enter from capillaries?
interstitial fluid (IF)
where do CO2 and waste products enter from the tissues?
capillaries/bloodstream
virtually all gases, nutrients, metabolites, and water are continuously exchanged via…
capillary exchange
what is exchanged in “capillary exchange”?
gases
nutrients
metabolites
water
what is between the external interstitial fluid and plasma inside the capillary?
endothelial cells
*single layer
*semipermeable
T/F: capillaries have smooth muscle in their walls
FALSE
capillaries do NOT have smooth muscle in their walls
controlled by the large arterioles
*constricting their capillary sphincters
how do capillaries help in temperature regulation?
cool down via heat loss: vasodilation (increases blood flow)
warm-up via prevent heat loss: vasoconstriction (decreases blood flow)
how do capillaries respond to hot weather?
HEAT LOSS
vasodilation (increased blood flow)
cools down body
how do capillaries respond to cold weather?
PREVENT HEAT LOSS
vasoconstriction (decreased blood flow)
warms body up (bluish hands/feet)
if the precapillary sphincter is closed what happens?
precapillary sphincter closed =
blood flows only through the metarteriole and thoroughfare channel (center of the capillary)
not branching out to capillary bed
if the precapillary sphincter is open what happens?
precapillary sphincter open =
blood flows through capillary beds