Midterm 1 - Blood Volume Microcirculation and Fluid Exchange Flashcards
what percentage of blood do capillaries contain
about 5%
what are capillaries the site of
water-nutrients-wastes-gases exchange with interstitial fluid and tissues
how large are capillaries in diameter
7-8 um
how long are capillaries
0.5 mm
what are red blood cells in diameter
approx. 7.5 um
what are capillaries made of
a single layer of endothelial cells
what are capillaries formed in
dense netowkrs
how close is each cell of a tissue to a capillary
within 100 um
where do capillaries receive blood from
smallest arterioles and metarterioles
metarterioles
connection between arteriole and capillaries network
what does the density of capillaries vary depending on
the metabolic activity of the tissue
what do met arterioles possess
rings of smooth muscle tissue that can open and close on demand
what are met arterioles doing during exercise
all open
what is the consequence of the small diameter
a very slow flow
what is resistance reduced by in capillaries
the extent of the parallel ramifications
what does trans capillary diffusion depend on
capillary type and substance properties
what does transcapillary diffusion follow
gradient between blood and interstitial fluid
what do most capillaries have that allow transfer of water and lipid-insoluble molecules
pores or clefts
what do the size and number of pores in a capillary depend on
the tissue
what type of substances exchange freely across cell membrane
lipid soluble (O2 and CO2)
what capillaries are fenestrated
intestine
liver
kidney
what does it mean for capillaries to be fenestrated
vesicles fuse to form large gaps across endothelial cell membrane