WESLEY D, ANDERSON 
781 
Aortic arch 
Cranial (superior) 
vena cava 
Rt marginal a 
I 
Rt or acute margin 
Brachiocephalic trunk 
Descending aorta 
Ligamentum arteriosum 
Left pulmonary a 
Pulmonary trunk 
Pulmonary vv. 
Left atrium 
Great cardiac v. 
Cranial (anterior) 
interventricular a. 
Obtuse margin 
Caudal (posteri 
ventricular a 
Coronary sinu 
Rt pulmonary aa. 
Cranial (superior) 
' vena cava 
'p- Caudal 
? (inferior) 
vena cava 
Right 
yl atrium 
Rt marginal a. 
Small cardiac v. 
Middle cardiac v and 
caudal (posterior) interventricular br 
of left coronary a. 
Figure 15. — Sternocostal surface of ovine heart showing coronary arteries and great cardiac vein (left) and caudal 
(posterior) surface of ovine heart demonstrating terminations of coronary arteries and coronary sinus (right) . 
renal arteries, the azygos systems become im- 
portant collateral routes for return of venous 
blood from the caudal or lower extremities to 
the right atrium. 
ARTERIAL SUPPLY TO THE SPINAL CORD 
In the thoracic region, aortic aneurysm or 
aortic bypass may seriously compromise blood 
supply to the spinal cord. Infarction of the 
spinal cord in human beings with cardiovascular 
disease has been reviewed by Henson and Par- 
sons,* and in recent years innovations in diag- 
nostic neuroradiology and microsurgery have 
initiated a resurgence of interest in spinal cord 
circulatory dynamics which have resulted in a 
greater appreciation of vascular pathology. As 
a result of the renewed awareness of the anat- 
omy of the arterial supply to the spinal cord, 
Burton ^ has expressed the opinion that the in- 
cidence of spinal cord vascular disease in man 
remains to be determined. 
In quadrupeds, the ventral spinal artery 
arises at the level of the atlanto-occipital artic- 
ulation and courses caudally in the median 
ventral fissure of the spinal cord. The two dor- 
sal spinal arteries, which also arise from the 
vertebral arteries, are smaller than the ventral 
spinal and contribute less blood flow to the cord. 
The ventral spinal (as is the case for the an- 
terior spinal artery in man) is dependent upon 
reinforcing radicular branches from the verte- 
bral and dorsal intercostal arteries for adequate 
perfusion of the spinal cord. Figure 27 is an 
arterial cast of the arterial supply to the cervi- 
cal segments of the spinal cord of the sheep. The 
vertebral arteries give off spinal branches 
which at segmental levels terminate in radicular 
arteries in most mammals. The radicular 
branches anastomose with the small ventral 
spinal artery and thereby reinforce the arterial 
perfusion to the cervical segments of the spinal 
cord. Unfortunately the spinal and radicular 
