vasculature Flashcards
layers of blood vessel walls (from inner to outer)
tunica intima, tunica media, tunica adventitia, vasa vasorum (in larger vessels)
tunica intima
has layer of endothelial cells in intimate contact with blood. In larger arteries it has a layer of elastic and loose collagen tissues containing intimal cells
tunica media
may be made of multiple layers of elastic laminae, smooth muscle cells, or collagen
tunica adventitia
made of collagen
vasa vasorum
contained within adventitia in larger vessels, supplies O2 and nutrients to adventitia and outer part of media, which cannot get diffusion from th inside of blood vessels
arteries
thick-walled (= to lumen), largest arteries have thick media with elastic fibers w/ layers decreasing from the heart to the arterioles. Smooth muscle in media from aorta to arterioles
elastic arteries
aorta and large arteries, intima has thin layer of collagen/elastin-rich fibers and contains fibroblasts and myointimal cells (similar structual feature to smooth muscle cells). Media is very elastic, adventitia has vasa vasorum
muscular arteries
multiple elastic layers in elastic arteries become two well-defined elastic layers in muscular arteries, inner elastic lamina between intima and media, outer elastic lamina that defines the boundary between the media and adventitia, media is primarily made of smooth muscle cells. adventitia is think and contains collagen and elastin
arterioles
inner lining of endothelial cells on thin basement membrane, immediately surrounded by 1-2 layers of smooth muscle, outer collagenous tissue (blends with other CT), can greatly restrict flow to capillary beds. Metarterioles and arteriole-venule shunts can connect larger arterioles and venules and constriction bypasses cap beds
capillaries
smallest vessels, 1-2 endothelial cells surrounding lumen, have pericytes (give rise to smooth muscle during vessel growth and would healing) surround by collagenous fibrils, exchage occurs through diffusion. 2 main types: continuous and fenestrated.
continuous capillaries
endothelial cells form an uninterrupted lining, transfer can occur via pinocytotic vesicles
fenestrated capillaries
has pores in endothelial cells, some with a thin diaphram covering. Found in glomerulus of kidney, permit bulk flow of plasma, sinusoidal caps the endothelial cells are split by wide pores large enough to permit red clood cells and plasma to pass as in the spleen and liver
post-capillary venules
caps drain into these, similar in structure to caps but larger diameter, urrounded by pericytes, slow flow and leukocytes diapedese though vessel walls, endothelium responsive to vasoregulatory substances (serotonin and histamine), regions are sensitive to controlled permeability, larger venules get 1-2 layers of smooth muscle in media, tin connective adventitia
veins
thin-walled, wall thickness increases with diameter, small veins have intimal layers of endothelial with no elastic, media is primarily smooth muscle of 2-4 layers. Adventitia is collagenous and blends with CT surrounding, Medium-sized veins have increased thickness in advenitia (thickest layer), large have thin intima and a media of interlayered smooth muscles and collagen fibers with small elastin fibers and adventitia is thick and ha vasa vasorum.
blood flow in veins
hydrostatic pressure, contraction of smooth muscle and skeletal muscles, important in legs overcoming gravity. Have one-way flap valves to prevent backflow, loss of function of flaps can cause vein expansion (varicose veins)
