Histological Study on the Sinu-Atrial Node of Turkey

Histology of the SAN was studied in 5 female turkeys by using routine histological techniques. The SAN was lied in the region between the orifices of the right cranial vena cava and of the caudal vena cava and beneath the atrial epicardium. Its shape was conical to a limited degree. Its cranial end was near the right auricle and it was narrower than the caudal end. The caudal end was near the lateral wall of the atrial wall of the right atrium. At the caudal end of the SAN there were cellular chains which leaved the node to enter surrounding atrial myocardium. These cells were narrower and lighter than the myocardial fibers. The SAN of turkey had no central artery. Histologically, it was contained a very little collagen and the nodal cells were mainly located as cellular strands which were narrower than the ordinary myocardial fibers. Since, the nodal cells contained less myofibril than ordinary myocardium; therefore, they were distinctively paler. At the junction between the nodal cells intercalated discs were not seen.