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The tunica externa is made from collagen and elastic fibers in a loose connective tissue. [1] [2] This is secreted by fibroblasts. [1]This is normally the thickest tunic in veins and may be thicker than the tunica media in some larger arteries.
Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane (also called the external elastic lamina). This structure is not usually seen in smaller arteries, nor is it seen in veins. [5]
External lamina is a structure similar to basal lamina that surrounds the sarcolemma of muscle cells. It is secreted by myocytes and consists primarily of Collagen type IV, laminin and perlecan (heparan sulfate proteoglycan). Nerve cells, including perineurial cells and Schwann cells also have an external lamina-like protective coating. [1]
It consists of circularly arranged elastic fiber, connective tissue and polysaccharide substances; the second and third layer are separated by another thick elastic band called external elastic lamina. [7] The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel. Veins do not have ...
Small vessels like vasa vasorum and vasa nervorum are particularly susceptible to external mechanical compression, [10] and thus are involved in pathogenesis of peripheral vascular and nerve diseases. A tear in vasa vasorum situated in tunica media layer of aorta may start pathologic cascade of events leading to aortic dissection. [4]
Only the larger muscular arteries possess an external elastic lamina. The adventitia, the outermost layer, contains lymphatic capillaries, vasa vasorum, and nerves, which may extend into the outer parts of the media. [2] Under the microscope, muscular arteries can be identified by their clearly defined internal elastic lamina. In constricted ...
Lose Your Senses. Our bedrooms should be dark, quiet and cool for the best night’s sleep, says Dr. Roban. She suggests using ear plugs or white noise to block out external noise; black out ...
Micrograph showing the internal elastic lamina (thin pink wavy line - image edge mid-left to image edge bottom-centre-left). H&E stain. The internal elastic lamina or internal elastic lamella is a layer of elastic tissue that forms the outermost part of the tunica intima of blood vessels. It separates tunica intima from tunica media.