Capillaries Flashcards
what are the 4 types of capillaries?
sinusoidal (sinusoid are large sinusoidal)
continuous
fenestrated
what does a capillary wall consist of?
endothelial cells (simple squamous epithelium)
basement membrane
delicate layer of loose CT
scattered pericapillary cells that are fibroblasts, macrophages or undifferentiated smooth muscle cells
how do substances move into and out of the capillary?
diffuion
what type of molecules can move through the plasma membrane of a capillary?
lipid soluble and some small H2O soluble
how do large, H2O soluble molecules pass through the capillary into the blood?
through fenestrae or gaps between the endothelial cells
what type of capillary has no gaps between the endothelial cells, and no fenestrae?
continuous
describe a continuous capillary
no gaps btwn endothelial cells
no fenestrae
less permeable to large molecules than other capillary types
where are you most likely to find continuous capillaries?
muscle or nervous tissue (tissues that can depolarize and excess ion movement into and out of the blood would interfere with electrical properties of the tissue)
what type of capillary has pores through the cells?
fenestrated
describe a fenestra of a capillary’s endothelial cell
an area where cytoplasm is absent and plasma membrane is made of a thin, porous diaphragm
describe the funtion of a fenestrated capillary
highly permeable
describe a fenestrated capillary
have pores through the cell
each cell may have many fenestrae
highly permeable
where are you most likely to find fenestrated capillaries?
intestinal villi, ciliary processes of the eye, choroid plexus, glomeruli of kidney
what is a capillary with a large diameter and large fenestrae?
sinusoidal
describe a sinusoidal capillary
less basement membrane
large diameter
large fenestrae
may have gaps between endothelial cells
