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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 endothelial cells are in direct contact with the blood flow.
Tunica muscularis refers to muscular layers in the walls of hollow organs such as the gut, where they are required for peristalsis, and sometimes for sphincters. [7] Tunica serosa is the serous membrane [7] Tunica vaginalis is the serous covering of the testis within the scrotum. [6] Tunica vasculosa could refer
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.
The three layers of the vein wall are the outer tunica externa, the middle tunica media and the inner tunica intima. There are also numerous valves present in many of the veins. The outer tunica externa, also known as the tunica adventitia is a sheath of thick connective tissue. This layer is absent in the post-capillary venules.
Endothelium lines the inner wall of vessels, shown here. Microscopic view showing endothelium (at top) inside the heart. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. This forms a barrier between vessels and tissues and control the flow of substances and fluid into and out of ...
The externa, alternatively known as the tunica adventitia, is composed of collagen fibers and elastic tissue—with the largest arteries containing vasa vasorum, small blood vessels that supply the walls of large blood vessels. [3] Most of the layers have a clear boundary between them, however the tunica externa has a boundary that is ill-defined.
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. In smaller vessels it penetrates only the outer layer. In the smallest vessels, the vessels' own circulation nourishes the walls directly and they have no vasa vasorum at all.
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.