Anatomy_Key Terms_Ch20 Flashcards
lumen
central blood-filled space of a blood vessel
tunica intima
innermost tunic of a blood vessel
endothelium
simple sqamous epithelium that lines the lumen of all vessels
subendothelial layer
a thin layer of loose connective tissue just external to the endothelium in vessels larger than about 1mm in diameter
tunica media
middle tunic, consists primarily of circularly arranged sheets of smooth muscle fibers, between which lie circular sheets of elastic and collagen fibers
tunica externa
or tunica adventitia, layer of connective tissue that contains many collagen and elastic fibers, cells and fibers run longitudinally; protects the vessel, further strengthens its wall, and anchors the vessel to surrounding structures
vasa vasorum
”"”vessels of the vessels””, tiny arteries, capillaries, and veins in the tunica externa of the larger arteries and veins”
arteries
vessels that carry blood away from the heart; oxygen-rich blood for the systemic circuit, oxygen-poor blood in the pulmonary circuit
elastic arteries
largest arteries near the heart (aorta and its major branches) with diameters ranging from 2.5 cm to 1 cm, sometimes called conducting arteries
muscular (distributing) arteries
lie distal to the elastic arteries and supply groups of organs, individual organs, and parts of organs, range in diameter from about 1 cm to 0.3 mm
internal elastic membrane
forms the outer layer of the tunica intima (of muscular arteries)
external elastic membrane
forms the outer layer of the tunica media (of muscular arteries)
arterioles
smallest artiers, diameters ranging from about 0.3mm to 10um, tunica media contains only one or two layers of smooth muscle cells
capillaries
smallest blood vessels, diameter of 8-10 um, just large enough to enable erythrocytes to pass through in single file
intercellular clefts
gaps of unjoined membrane that allow small molecules to pass into and out of the capillary<br></br>most small molecules are exchanged through the intercellular clefts. in sinusoids, larger molecules and cells are exchanged through the wide intercellular clefts.
pericytes
spider-shaped contractile stem cells whose thin processes form a widely spaced network around the capillary, strengthen and stabilize capillary and help control permeability
continuous capillaries
most common type of capillary, tight junctions and occasional desmosomes hold the capillary endothelial cells together
fenestrated capillaries
“joined by tight junctions and contain intercellular clefts, have poors (fenestrations, or ““windows””) spanning the endothelial cells, occur only where there are exceptionally high rates of exchange of small molecules between the blood and the surrounding tissue fluid (e.g. small intestine, kidneys, endocrine glands, synovial membranes of joints)”
sinusoid capillaries/sinusoids
wide, leaky capillaries, occur wherever there is an extensive exchange of large materials e.g. proteins or cells between the blood and surrounding tissue (e.g. bone marrow, spleen)
diferect diffusion through the endothelial cell membranes
carbon dioxide and oxygen seem to be the only important molecules that diffuse directly through endothelial cells, because these unchanged molecules easily diffuse through the lipid-containing membranes of cells
fenestrations
in fenestrated capillaries, the pores in the endothelial cells allow passage of many small molecules
pinocytotic vesicles
pinocytotic vesicles invaginate from the plasma membrane and migrate across the endothelial cells, transporting dissolved gases, nutrients, and waste products into the capillary
microvascular unit
an arteriole, the capillary bed it feeds, and the venule that drains the capillary bed, together
metarteriole
with the thoroughfare channel comprise a vascular shunt that allows blood to bypass the true capillaries
most small molecules are exchanged through the intercellular clefts. in sinusoids, larger molecules and cells are exchanged through the wide intercellular clefts.