Comparative anatomy of the cardiac foramen ovale in cats (Felidae) , dogs (Canidae) , bears (Ursidae) and hyaenas (Hyaenidae)
Macdonald, A.A.; Johnstone, M.
Journal of Anatomy 186: 235-243
1995
ISSN/ISBN: 0021-8782 PMID: 7649822 Document Number: 454855
The foramen ovale was examined in newborn or fetal cats (9), dogs (8) and bears (2; species unknown), snow leopards (2; Uncia uncia), ocelot (1; Leopardus pardalis), lions (2; Panthera leo), panther (1; P. pardus), tigers (3; P. tigris), golden jackal (1; Canis aureus), wolf (1; C. lupus), red foxes (3), dhole (1; Cuon alpinus), brown bear (1; Ursus arctos), grizzly bear (1; U. arctos horribilis), polar bear (1; U. maritimus), and striped hyaena (Hyaena hyaena). In each species, the foramen ovale, when viewed from the terminal part of the caudal vena cava, had the appearance of a short tunnel. A thin fold tissue, the developed remains of the embryonic septum primum, extended from the distal end of the caudal vena cava for a variable distance into the lumen of the left atrium and contributed towards the 'tunnel' appearance in all specimens. It constituted a large proportion of the tube, and its distal end was straight-edged. There was fibrous material underlying the endothelium of the flap, the apparent morphology of which suggested that it comprised cardiac muscle. In each species, the pulmonary veins drained from close beside the interatrial septum and this venous drainage seemed to be directed along the length of the flap of tissue on its dorsal surface. Collapse of the 'tunnel' of the septum primum effected closure of the foramen ovale in most of the newborn studied. When closed, the tissue flap appeared to be anchored to the interatrial septum along the surface of the crista dividens which lay in the left atrium. The straight edge at the end of the 'tunnel' remnant was not usually attached and, when gently lifted, formed a small blind-ended pouch ending at the attachment of the flap to the crista dividens.