Objective: To provide information about the anatomy and histology
of the cardiac sinu-atrial node of rat. This information is needed in various fields of veterinary sciences, such as anatomy, histology, physiology, pathology and cardiology.
Design: Compare the anatomy and histology of the rat with the
available data on the sinu-atrial node of human being and other animals.
Animals: Four male rats.
Procedure: A piece consisted of the upper part of the interatrial septum along with the right cranial vena cava and a part of lateral wall of right atrium and right auricle was separated from each heart.
The sinu-atrial node was studied by using routine anatomical and
histological techniques. Results: The sinu-atrial node of the rat was almost triangular in shape. The mean dimensions of the node were 225tm in length,
83iim in width and 216itm in thickness. The cells of the node were
organized into groups and chains of cells. In general, the color differences between the nodal cells and the ordinary myocardial fibers of the right atrium were very weak and there were no intercalated
discs at intercellular connections. Also, the cells near the sinu-atrial node artery were organized around it. Conclusion: The anatomical location of the sinu - atrial node in
the rat is similar to those of human being, dog, cattle, horse, camel,
cat and goat. In the heart of rat there was a central artery. In this respect, it was resemble to those of human being, dog and camel. However, in gaot, sheep, rabbit, cat, cattle and guinea pig there is
no central artery in the node. There was a little amount nerve fibers
within the sinu-atrial node of rat. In this respect, it is similar to that of guinea pig. Whereas, in man, horse, dog, cat and goat the nerve
fibers are aboundant within the node. J. Fac. Vet. Med. Univ. Tehran 59,1:3-7,2004.