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ANATOMY AND PATHOLOGY 
Dorsal (post.) vagal tk. 
Ventral (ant) vagal tk 
R1 pulmonary v Middle cervical gang i 
Rt. principal bronchus Costocervical tk. 
Common carotid a. Ext. jugular v. 
a a V 
Rt. atrium a rt. vei^^i^Ki • 
covered by visceral l^jei 'ofi 
serous pericardium (ebra 
Thymic br 
Rl ptfrenic n. 
\ 
Pericardiacophrenic a. 
Crania|/Sup.) vena cava 
Costal cartilage 
Mediastinal adipose tissue 
Cut edge of fibrous pericardium a parietal 
layer of serous pericardium 
Figure 12. — Right surface of heart, great vessels and associated thoracic structures, sheep. 
The right coronary artery in mammals arises 
from the ascending aorta within the right aortic 
sinus, emerges deep to the right side of the pul- 
monary trunk and courses around to the back 
of the heart in the coronary sulcus. It gives 
origin to tiny descending myocardial branches, 
a larger right marginal artery on the acute sur- 
face of the heart, and in sheep, calf and dog 
terminates on the caudal surface as small un- 
named branches which descend toward the apex 
of the heart. In man, cat and horse however 
the right coronary artery terminates on the pos- 
terior surface of the heart as the posterior inter- 
ventricular artery (Figure 17). 
The majority of the cardiac veins parallel 
coronary arteries in most quadrupeds like they 
do in man (Figure 18). The largest tributary 
of the coronary sinus in most mammals, the 
great cardiac vein, ascends from the apex of the 
heart in the interventricular sulcus and near the 
origin- of the circumflex branch of the left cor- 
onary artery it turns sharply to the left and 
passes around the heart in the coronary sulcus. 
Also in most animals, as is the case in man, the 
tiny oblique vein of the left atrium marks the 
change in name from the great cardiac vein to 
coronary sinus (Figure 19). Of considerable 
importance to the investigator sampling venous 
blood from the myocardium is that in the sheep 
and calf the coronary sinus is joined by the 
left azygos (formerly called the hemiazygos) 
vein before emptying into the right atrium. 
Therefore one sampling venous blood from the 
terminal portion of the coronary sinus in these 
species is sampling venous return from the 
thoracic wall and abdomen as well as from the 
myocardium. 
The internal anatomy of the heart of sheep, 
i 
