This investigation was supported in part by grants HE 19,835–03 and GM-1052 from the National Institutes of Health and a grant from the Central Ohio Heart Association.
Morphology of the specialized conducting tissue in the atria of the equine heart†
Article first published online: 27 JAN 2005
Copyright © 1967 Wiley-Liss, Inc.
The Anatomical Record
Volume 158, Issue 4, pages 401–415, August 1967
How to Cite
Bishop, S. P. and Cole, C. R. (1967), Morphology of the specialized conducting tissue in the atria of the equine heart. Anat. Rec., 158: 401–415. doi: 10.1002/ar.1091580405
- Issue published online: 27 JAN 2005
- Article first published online: 27 JAN 2005
The gross and microscopic anatomy of the sinus node (SN), atrioventricular node (AVN) and specialized fibers in the atrium were studied in 19 horses and eight mules. The SN is supplied with blood by a branch from the left circumflex artery which subdivides within the node. The SN has a body and long tapering cranial and caudal crura which encircle the lateral margin of the precaval orifice. The AVN, which has no large artery consistently present within its structure, is located within the fibrous septum above the septal leaflet of the tricuspid valve and anterior to the coronary sinus.
Histologically most of the fibers in the SN and AVN are similar to those in other species. They are smaller, paler staining and much more interwoven than ordinary myocardial fibers. In the caudal crus of the SN, the fibers are clumped together with loss of individual characteristics.
Large, glycogen-rich cells morphologically similar to ventricular Purkinje fibers are found in the right atrial subendocardium. The distribution of these fibers suggest that they may be concerned with intraatrial spread of excitation. Muscular pathways between the SN and AVN are composed of ordinary myocardial fibers. The large atrial myocardial fibers do not connect directly with SN or AVN fibers.