Ultrastructure of cardiac myocyte in the Asian elephant (Elephas maximus)

Cardiac myocytes of an Asian elephant (Elephas maximus) were observed by transmission electron microscopy. Typical ultrastructural features of cardiac myocytes are exhibited in the musculature of both the left and right atria, and left ventricle of the heart. Myofibrils, mitochondria, T-system and sarcoplasmic reticulum are well-developed within the cytoplasm. Many mitochondria are characteristically concentrated is some myocytes. Cardiac musculature is also distributed in the root of the caudal vena cava. Many atrial granules are detected not only in atrial myocytes, but also in the myocytes of the caudal vena cava. Atrial natriuretic polypeptide may be secreted from the caval venous wall in the elephant.