ANAT 261 Lecture Notes - Arteriole
15 Mar 2012
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Document Summary
Endothelium: lines the luminal surface of all blood vessels: simple squamous, runs longitudinally (along axis of vessel, in cross section will also appear in cross. Smooth muscle: runs circularly (perpendicular to endothelial cells) internal elastic limiting membrane: looks wavy layers of tissue (from lumen outwards): none in veins, distinguishing factor of muscular arteries, tunica intima, tunica media, tunica adventitia (connective tissue) Media: large layer of alternating smooth muscle layers and elastic membranes. Adventitia: usually 10+ layers of cells, dense irregular connective tissue, contains vasa vasorum (small capillaries that nourish the tissue of the artery) Muscular arteries smaller than elastic arteries, but still bigger than arterioles intima: endothelium, sub-endothelial layer, and very distinct ielm. Arterioles small lumen intima: only endothelium; no visible ielm. Often in proximity to large elastic arteries. Difficult to distinguish from middle-size veins, but often too large for field of microscope intima: endothelium; very little sub-endothelial layer; no ielm. Media: thin; few layers of smooth muscle.
