Sinu-Atrial Node of Mature Dromedary Camel Heart (Camelus dromedarius) with Special Emphasis on the Atrial Purkinje Like Cardiomyocytes

Abstract

The sinu-atrial node (SAN) is one of the impulse conducting system of the camel heart. Anatomically, it lies beneath the epicardium, at the cranial end of the terminal sulcus, near the junction between the superior vena cava to the lateral wall of the right atrium and the right auricle. Histologically, SAN is located in the subepicardial layer of the terminal crest and can be identified as a mass of specialized and modified cardiac myocytes. Moreover, it appeared elongated in shape and bent oblong. SAN appears strongly similar to the general structure of the glands where, it is formed of two parts; the stroma and the parenchyma. The stroma is consisted of a fibrous connective tissue capsule that is completely investing the SAN from all sides. From the capsule, thin connective tissue septa or trabeculae are extending to inside the node, dividing the later into lobes. These lobes form the SAN head or the SAN body. From this body, the SAN arms processes take their way out. These arms are considered the internodal and interatrial pathways to the different sites in the right and left atria. So, the SAN head with arms giving the octopus like-appearance for the node. The parenchyma is consisted of three different types of specialized and modified cardiac myocytes; the perinuclear clear zone cells (“P” cells), the transitional cells (“T” cells) and the atrial Purkinje like cells or Purkinje like conducting cells.