Anatomical location and arterial blood supply of sinoatrial node in Caspian miniature horse


Department of Basic Sciences, Faculty of Veterinary Medicine, Karaj branch, Islamic Azad University, Karaj, Iran


BACKGROUND: Caspian miniature horse is an Iranian breed of the horse. Some anatomical studies such as topography of the heart have been conducted in recent years. Objectives: Regarding the importance of SA node in regulating the rhythmic contraction of heart, the present study was performed to demonstrate the position of the SA node and its arterial supply. Methods: 4 excised hearts of Caspian miniature horse were used for this study.  The coronary arteries in two horses were injected with a mixture of gelatin and choromopaque and the other two with colored rodopas. The gelatin injected specimens were used for contrast radiography and the rodopas injected specimens were macerated in HCl and the cast  studied for arterial branches. Terminal sulcus and location of SA node was macroscopically detected and separated for histological investigation. Results: Our study showed that the SA node is a small mass of transformed cardiac muscle. It is situated under the epicardium of the right ventricle between the cranial vena cava and the right auricle. The blood is supplied by a few branches separated from the right auricular branch of the proximal branch of left atrial artery. The latter itself is a branch of the left circumflex artery of the left coronary artery.


Bleeker, W.K., Mackaay, A.J.C., Masson-Pevet, M., Bou, I.N., Becker, A.E. (1980) Functional and morphological Organization of the rabbit sinus node. Circ Res. 46: 11-12.
Bishop, S.P., Cole, C.R. (1967) Morphology of the specialized conducting tissue in the atria of the equine heart. Anat Rec. 158: 401-416.
Dursun, N. (1975) Arteries of the heart in the horse and Calf. Ann Med Vet. 119: 391-410.
Frink, R.J., Merrick, B. (1974) The sheep heart: Coronary and conduction system anatomy with special reference to the presence of an os cordis. Anat Rec. 179: 189-199.
Gavaliatsis, I.P. (2000) “Right posterior” sinus node artery. Int J Cardio. 75: 301-303.
Ghazi, S.R., Tadjalli, M. (1996) Anatomy of the sinus node of camels (Camelus dromedarius). Anat Histol Embryol. 25: 37-41.
Ghazi, S.R., Tadjalli, M., Baniabbas, A. (1998) Anatomy of the sinus node of domestic cats (Felis catus). J Appl Anim Res. 14: 57-64.
Ho, Y.S., Anderson, R.H., Sanchez-Quintana, D. (2001) Atrial structure and fibers: morphologic bases of atrial conduction. Cardiovas Res. 54: 325-336.
James, T.N. (1961) Anatomy of human sinus node. Anat Rec. 141: 109-116.
James, T.N. (1962) Anatomy of sinus node of the dog. Anat Rec. 143: 251-256.
James, T.N. (1965) Anatomy of the sinus node, A-V node and os cordis of the beef heart. Anat Rec. 153: 361-364.
James, T.N. (1967) Anatomy of the cardiac conduction system in the rabbit. Circ Rec. 20: 638-648.
Nabipour, A. (2012) Comparative histological structure of the sinus node in mammals (Review Article). Turk J Vet Anim Sci. 36: 463-469.
Nabipour, A., Khonzadi, S., Moradi, G.H. (2000) Anatomy of the sinu-atrial node in the heart of Goat (Capra hircus). J Fac Vet Med Tehran Uni. 55: 93-96.
Nickel, R., Schummer, A., Seiferle, E. (1981) The circulatory system, the skin, and the cutaneous organs of the Domestic Mammals.  (2nd ed.) Verlag paul Parey, Berlin, Germany.
Ozgel, O., Haligur, A.C., Dursun, N., Karakurum, E. (2004) The macroanatomy of coronary arteries in donkeys (Equus asinus L.). Anat Histol Embryol. 33: 278-83.
Rodrigues, C.,  Borelli, V. (1988) Contribution to the study of the arterial vascularization of the sinuatrial node in sheep (Ovis aries Linnaeus, 1758). Revista da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo. 25: 207-217.
Pinto e Silva, P., Borelli, V. (1969) Arterial blood supply to the sino-atrial node in Friesian cattle. Arqs Inst Biol S Paulo. 36: 67-84.
Severino, R.S., Carneiro e Silva, F.O., Drummond, S.S., Alves, F.P., Beletti, M.E. (2000) Topographical and histological study of the Sinoatrial node in pigs. Braz J Morph Sci. 17: 55-58.
Sharma, D.N., Prasad, J. (1976) Anatomy of the cardiac conducting system of Indian buffalo (Bubalus bubalis). Har Vet. 15: 88-94.
Getty, R. (1975) Sisson and Grossman’s Anatomy of the Domestic Animls. (5th ed.) W.B. Saunders co. Philadelphia, USA.
Wang, K., Ho, S.Y., Gibson, R.H. (1995) Architecture of the atrial musculature in humans. Br Heart J. 73: 559-565.