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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.
The structure of the vasa vasorum varies with the size, function and location of the vessels. Cells need to be within a few cell-widths of a capillary to stay alive. In the largest vessels, the vasa vasorum penetrates the outer (tunica adventitia) layer and middle (tunica media) layer almost to the inner (tunica intima) layer.
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.
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.
Some theorize that the lamina lucida is an artifact created when preparing the tissue, and that the lamina lucida is therefore equal to the lamina densa in vivo. [7] The term "basal lamina" is usually used with electron microscopy, while the term "basement membrane" is usually used with light microscopy. Examples of basement membranes include:
Diagram showing Bowman's capsule as part of the renal corpuscle. The process of filtration of the blood in the Bowman's capsule is ultrafiltration, and the normal rate of filtration is 125 ml/min, equivalent to 80 times the daily blood volume. [citation needed] It is a major site for blood filtration (including glomerulus)
The lamina propria is a loose connective tissue, hence it is not as fibrous as the underlying connective tissue of the submucosa. [4] [self-published source?] The connective tissue and architecture of the lamina propria is very compressible and elastic, this can be seen in organs that require expansion such as the bladder. [5]