Morphological examinations conducted on adult gilts indicate that the dorsal nasal, frontal and facial veins belong to the myoelastic type with a well-developed internal elastic lamina and a thick tunica media with elastic fibers. Smooth muscle cells in the tunica media are mainly arranged circularly. A characteristic feature of individual veins, and even their parts, was the difference in the distribution and number of elastic fibers and amount of collagen, both in the internal elastic lamina and tunica media. Slight thickening of the vessel walls and a decrease in the number of elastic fibers were observed in the distal part of the dorsal nasal vein and in the proximal parts of the frontal and facial veins. No valves were found in the frontal vein. The bundles of smooth muscle cells in the tunica media and elastic fibers surrounding them were rounded, not laminar like in the other veins. Characteristic, sandwich-like arranged smooth muscle bundles, elastic fibers and large amounts of collagen were observed in the tunica media of the distal part of the facial vein. A distinctive feature of the middle auricular and radial veins was the presence of a well-visible external elastic lamina in the adventitia. An evaluation of the luminous vein surface in a SEM shows that endothelial cells are elongated and arranged consistently with the direction of blood flow in almost all of the veins analyzed. Endothelial cells were less elongated in the distal part of the facial vein, and microvilli were present on them.
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