Microscopical and ultrastructural studies of the renal artery in domestic swine.

Both renal arteries from six, 8-month old, Camborow hybrid pigs were examined in histological, semithin and ultrathin sections. It was established that the membrana elastica interna showed an expressed degree of wrinkliness. In certain sections, sometimes occupying 20% of the diameter of across-section, its curves were considerably higher and wider than those in the remaining part. The inner elastic membrane in these sections was cleaved in two layers. Estates of lengthwise-situated smooth muscle cells of an elliptical form were located in the middle shell (tunica media). Furthermore, a great quantity of mast cells were found in the middle shell. The electron-microscopic observations showed that their granules had various sizes and shapes. The outer shell (tunica adventitia) had an irregular thickness. In some parts, a few elastic fibres entered the middle shell. They had a tuft-like shape with a wedge-like or elongated configuration, and were situated among the layers of smooth-muscle cells.