Tunica adventitia

Three continous layers can be shown in the wall of embryonic human aorta. The innermost layer contains undifferentiated SMC, the intermediate layer consists of differentiated cells. In the outermost layer, possibly destinated to become the tunica adventitia, there are fibroblasts/generic mesenchymal cells [22]. At the same time, SMC become linked to the developing elastic laminae by bundles of microfibrils [23], giving rise to contractile-elastic units , i.e., a continous line of structures that link adjacent elastic laminae. Contacts between differentiating SMC and endo-... 

Wall morphology Complete tunica adventitia, external elastic lamina, tunica media, internal elastic lamina, tunica intima. ... 

A well-developed tunica adventitia and vasa vasorum, although wall layers are gradually thinning) ... 

Well-developed tunica media and external elastic lamina, but tunica adventitia virtually nonexistent) ... 

Wall morphology Essentially the same as comparable major arteries but a much thinner tunica intima, a much thinner tunica media, and a somewhat thicker tunica adventitia contains a vasa vasorum... 

Venous return of blood to the heart starts with its movement through the postcapillary venules, which coalesce to form larger veins. Histologically, the transition from capillary to vein is marked by the measured appearance of smooth muscle cells within the tunica media of the vessel wall and collagen and elastic fibres within the tunica adventitia. 

Complete tunica adventitia, external elastic lamina, tunica media, internal elastic lamina, tunica intima, subendothelium, endothelium, and vasa vasorum vascular supply Main branches 32 5 mm-2.25 cm 3.3-6 cm —2 mm 83.2 ml... 

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