Contribution to the study of topography and histology of the sinoatrial node in Landrace swines

Abstract

The topography and the histological aspects of the sinoatrial node in Landrace swines were determined by examining serial fragments, extracted from four animals (2 males and 2 females) belonging to the aforementioned race: these fragments were submitted to different coloration methods. The observations in these preparations were: 1) the sinoatrial node is situated at the junction of the cranial vena cava with the right atrium, more precisely, in all extension of the terminal groove and cavoatrial dihedral angle. 2) The cells of the nodal tissue, rich in glycogen, have oval or round-shaped nuclei, loose chromatin , clear nuclei involved by lucent halo and with acidophilic cytoplasm; they also show myofibrils which are sinuous but less striated when compared to the ones of an ordinary miocardium. These cells are covered by connective tissue where collagenic and elastic fibers are predominant; and the nodal formation is followed by arterial vessels of medium and light caliber, as well as by veins, nerves and even ganglion cells.