Translations:Blutgefäße/3/en

1. The tunica interna (intima) is the innermost wall and consists of a continuous single row of endotheliumcells lying in the longitudinal direction of the vascular flow. It serves as a barrier to the tissue. The endothelium is separated from the wall by a basement membrane. It is a very smooth layer that ensures unimpeded blood flow. The second layer (Membrana elastica interna) is a thin layer of connective tissue (subendothelium). Here, Arteries has more elastic fibers. The tunica media (media) consists mainly of smooth muscles, in the veins thinner than in the large arteries, between which elastic material and collagenous fibrils lie. The collagen fibrils reduce the elasticity of the venous tube # The tunica externa (adventitia) has important functions in the supply and innervation of the blood and lymph vessel system. In addition, it forms a displacement bearing and a demarcation from neighbouring structures. Depending on the type of vessel, collagene and elastic fibres occur to varying degrees. It does not necessarily set itself off cleanly from its surroundings because its collagen fibres radiate into the surrounding tissue.