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A common pathological disorder concerning the tunica externa is scurvy, also known as vitamin C deficiency. Scurvy occurs because vitamin C is essential for the synthesis of collagen, and without it, the faulty collagen cannot maintain the vein walls and rupture, leading to a multitude of problems.
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]
The tunica intima of muscular arteries features a thin subendothelial layer and a prominent internal elastic lamina, while the media may contain up to 40 layers of large smooth muscle cells interspersed with a variable number of elastic lamellae, depending on the vessel size. Only the larger muscular arteries possess an external elastic lamina.
A thin membrane of elastic fibers in the tunica intima run parallel to the vessel. The middle layer of tunica media is the thickest layer in arteries. 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 ...
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]
The tunica intima (Neo-Latin "inner coat"), or intima for short, is the innermost tunica (layer) of an artery or vein.It is made up of one layer of endothelial cells (and macrophages in areas of disturbed blood flow), [1] [2] and is supported by an internal elastic lamina.
The tunica media is made up of smooth muscle cells, elastic tissue and collagen.It lies between the tunica intima on the inside and the tunica externa on the outside.. The middle coat (tunica media) is distinguished from the inner (tunica intima) by its color and by the transverse arrangement of its fibers.
Thick elastic fibers from the visceral pleura (outer lining) of the human lung. Elastic fibers are found in the skin, lungs, arteries, veins, connective tissue proper, elastic cartilage, periodontal ligament, fetal tissue and other tissues which must undergo mechanical stretching. [1] In the lung there are thick and thin elastic fibers. [3]