Unusual Muscle-related Morphological Features Detected in the Cranial Cava Vein in 10-day-old Broiler Chickens

Abstract

The birds, in contrast to mammals, have two cranial cava veins. The two cranial cava veins and caudal cava vein are the largest veins in chickens. In general, veins have a wall consisting of 3 tunics: intima, media, and adventitia. This study aimed to describe the microscopical structure of the left and right cranial cava veins in 10-day-old chicken broiler. Fragments from the left and right cranial cava veins were collected during the necropsy and were histologically processed by paraffin inclusion and stained with the Verhoeff-trichrome method. The left and right cranial vena cava have relatively thin walls compared to the lumen. The intima is formed by an endothelium, the media is formed by circular smooth muscle cells and the adventitia is formed by dense non-oriented connective tissue. A particular aspect is the fact that smooth muscle cells with a predominantly longitudinal orientation are present in the structure of the adventitia. Both in the left and right cranial veins, the proportion between the amounts of muscle tissue in the media relative to that in the adventitia is not identical on the entire circumference of the vessel. Moreover, in some areas of the venous wall, the quantity of muscle cells present in the tunica adventitia is higher than in tunica media.