378 DK. C. F. SONNTAG ON THE ANATOMY, 



As the pulmonaiy artery is mucli wider than that in Man, the 

 velocity and pressure of the blood in it must be relatively less 

 than in him, as can be shown by applying the laws of velocity 

 and pressure. 



The descending thoracic aorta extends from the sixth to 

 eleventh dorsal vertebrfe after which it passes into the abdomen. 

 It gives off the intercostal arteries to the lower ten intercostal 

 spaces, a small bronchial artery to the left lang, a large bronchial 

 artery to the right lung, and several branches to the thoracic 

 oesophagus, which anastomose with oesophageal branches of the 

 coeliac axis. The lower intercostal arteries supply the diaphragm. 



The abdominal aorta extends from the twelfth dorsal vertebra 

 to the lower border of the fourth lumbar vertebra, where it 

 divides into the two common iliac arteries. It is relatively 

 smaller, and its branches are fewer than in Man. The following 

 is the order of the branches from above downwards : — 



1. Phrenic artery. 



2. Coeliac axis. 



3. Superior mesenteric artery. 



4. Renal arteries. 



5. Right ovarian artery. 



6. Inferior mesenteric artery. 



7. Four lumbar arteries arising at different levels from the 

 back of the aorta. 



It does not give off any suprarenal arteries, nor is it continued 

 as a middle sacral artery. 



The phrenic artery is a large vessel arising from the left side 

 of the beginning of the abdominal aorta. It gives a small branch 

 to the left cms and left half of the diaphragm, and it is continued 

 over the right crus as a large vessel which sends branches to the 

 central tendon, the muscle fibres, the right crus, the process 

 arising from the second lumbar transverse process and the right 

 suprarenal capsule. 



Blood Supply to the Suprarenal Capsules : — Each capsule 

 i-eceives a vessel from the phrenic artery and the corresponding 

 renal artery, but none from the aorta. 



The Cceliac Axis (text-fig. 40, C.Ax) arises immediately above 

 the upper border of the pancreas, and it quickly divides into 

 hepatic, coronary, splenic, and inferior pyloro-duodenal arteries. 

 Of these the hepatic is by far the largest. 



The Hepatic Artery (H.A) first runs to the right and then 

 turns upwards to the liver. Between the layers of the gastro- 

 hcpatic omentum it divides into two branches ; and it lies in 

 front of the portal vein, and to the left side of the common bile- 

 duct. One of the two terminal branches (a) runs straight to 

 the liver and divides into two arteries which enter the portal 

 fissure. The other branch (b) runs in a convoluted course to the 

 right, gives off the cystic artery (c.a) to the gall-bladder and 

 divides into two arteries which sink into the right and left lobes 

 of the liver. 



