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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]
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 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.
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 ...
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 ...
Many adjacent epithelial tissues (which are avascular) get their nutrients from the interstitial fluid of areolar tissue; the lamina propria is areolar in many body locations. Its fibers run in random directions and are mostly collagenous, but elastic and reticular fibers are also present. Areolar tissue is highly variable in appearance.
Verhoeff's stain, also known as Verhoeff's elastic stain (VEG) or Verhoeff–Van Gieson stain (VVG), [1] is a staining protocol used in histology, developed by American ophthalmic surgeon and pathologist Frederick Herman Verhoeff (1874–1968) in 1908. [2] The formulation is used to demonstrate normal or pathologic elastic fibers.