-

Anatomy of the sinu - atrial node was studied in 5 female goats In the goat’s heart, the sinu - atrial node lied 0.18 mm - 0.25 mm beneath the epicardium, at terminal sulcus, near the junction between the cranial vena cava to, lateral wall of the right atrium and the right auricle, its shape was elongated and relatively cone shaped. Its cranial end was near the myocardium of the right auricle and caudal end was near the myocardiurn of atrial wall. The caudal end was narrower than the cranial end. Average of dimensions of the sinu - atral node were 12.75 mm x 1.5 mm x 1.7 mm. Histologically, the sinu - atrial node of goats contained normally a dense collagen frame and the cells with perinuclear clear zone (P) and transitional cells fE) were the principal cells of paranchyma. since these cells contained less myofilbrils than working myocardium , therefore , they were distinctively paler. The “p” cells were bigger than “T” cells and smaller than the ordinary myocardial cells. At the junction between “T” cells and “P” cells intercalated discs were not seen. The sinu - atrial node of goats lacked the central artery, but near the central section and toward the cranial margin there is a distinct arteriole that supplies the node.