what are the smallest and thinnest blood vessel?
what is the lumen diameter of capillaries?
the diameter of lumen of capillaries is big enough for what?
1 blood cell
what is the wall of capillaries made of
only tunica intima
capillaries have tunica media
what is the function of capillaries?
site of fluid and nutrients exchange
how are capillaries classified as
base on how porous they are
what are the three capillary classifications?
continuous, fenestrated, sinusoidal
what are continuous capillaries ?
endothelial cells joined by incomplete tight junctions
the incomplete junctions in continuous capillaries are called
what is the function of intercellular cleft
allow limited passage of fluid and small solutes; some solutes are moves by pinocytosis
what are pericytes
modified smooth muscles
what are the function of pericytes
help stabilize wall and filter solutes
where are continuous capillaries most common?
abundant in skin and muscles
what are fenestrated capillaries?
endothelial cells have pores in addition to he intercellular clefts
what are the pores in fenestrated capillaries called?
what are sinusoidal capillaries
endothelial cells which have larger fenestration and larger intercellular clefts
where are fenestrated capillaries found?
small intestine, kidneys, most endocrine glands
what are the most permeable capillaries
where are sinusoidal capillaries found?
liver, bone marrow, spleen, adrenal medulla
sinusoidal capillaries are important for immune function
where are immune cells located near?
what type of cells are near intercellular clefts?
phagocytic cells that eat bacteria in blood
capillary beds are networks of capillaries
flow of blood through the capillary beds from terminal arteriole to postcapillary venule
pathway blood takes when capillary bed is closed
metarteriole ---> thoroughfare channels
capillary beds consist of two types of vessels, what are they?
vascular shunts and true capillaries
connects arterioles to bed of 10 to 100 true capillaries
what is structurally in between arterioles and capillaries?
connects metarteriole to venule
what is structurally in between capillaries and venules ?
what are the smooth muscle fibers at the base of each true capillary
what is the function of precapillary sphincters
control blood flow into bed