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.

Scanning Electron Microscopic Studies on the Auricular and Atrio-ventricular Valvular Architecture of Pre-natal Non-descript Sheep

“…The subendothelial layer was present just below the endothelium and comprised of connective tissue fibers and conducting fibers (Fig 6). The present observations were in accordance with the findings of Ghonimi et al (2015) in camel and Sizer et al (2020) in Saanen goat. The fibers were interwoven with each other forming a network (Fig.…”

Histology of Sinoatrial Node in the Dromedary Camel Foetus

“…According to the available literature the present study reports for the first time that the SAN is present at the opening of cranial vena cava during the second and third trimesters of the dromedary camel foetus. It appears that the location of the SAN did not change during development in camels since its position in the foetus (this study) and adult hearts (Ghazi and Tadjalli, 1996;Ghonimi et al, 2015). It also remained the same in human (Titus, 1973), that is to say in the subepicardial region at the opening of the cranial vena cava in the right atrium.…”

“…SAN has been studied in many animals by different histological techniques which revealed a general agreement about its location, shape and cellular structure (Ghazi and Tadjalli, 1996;Nabipour, 2012;Ghonimi et al, 2015).…”

“…Similarly, Ghazi et al (1998) found that the sinus node of cats contained normally dense collagen framework. However, Ghonimi, et al (2015) claimed that the SAN of camel consisted of stroma and parenchyma. James (1970) stated that the sinus node was originated in the sinus venosus but subsequently a dense collagen framework developed.…”