ABDOMINAL CAVITY 391 



the medial branch curves forwards to the front of the central 

 tendon, and ends by anastomosing with its fellow and with 

 the terminal branches of the internal mammary artery. 

 Each inferior phrenic artery, in addition to the branches 

 which it supplies to the diaphragm, gives a twig, called the 

 superior suprarenal artery^ to the suprarenal gland. The left 

 artery sends a few minute branches to the oesophagus also. 



The inferior phrenic veins open into the inferior vena cava. 



The Middle Suprarenal Arteries (O.T. Middle Capsular 

 Arteries) are two small vessels which arise, one from each 

 side of the aorta, at the same level as the superior mesen- 

 teric. Each runs laterally and upwards, in front of a crus 

 of the diaphragm, to the suprarenal gland, into the substance 

 of which it sinks. The right middle suprarenal artery passes 

 behind the inferior vena cava. They anastomose freely with 

 the superior and inferior suprarenal arteries. 



The right suprarenal vein opens into the inferior vena cava, 

 whilst the left suprarenal vein ends in the left renal vein or 

 in the left inferior phrenic vein. 



The Renal Arteries. When compared with the organs 

 which they supply, the renal arteries are disproportionately 

 large. Only a small part of the blood which they carry 

 to the kidneys is used for the nourishment of the gland 

 substance. The kidneys are excretory organs, and it is 

 necessary that the blood should pass to them in large quantity 

 in order that certain materials may be removed from it. 



The renal arteries take origin, about a quarter of an inch 

 below the superior mesenteric, at the level of the second 

 lumbar vertebra. Each artery proceeds laterally, at right 

 angles to the aorta, and, approaching the kidney, breaks up 

 into three branches, which enter the hilum, and pass deeply 

 into the renal sinus. Each artery is overlapped by the ac- 

 companying vein. The right artery is placed at a slightly 

 lower level than the left, and passes behind the inferior vena 

 cava. At the hilum two of the terminal branches, as a 

 rule, lie between the renal vein and the pelvis of the ureter, 

 whilst the third enters the sinus behind the pelvis of the 

 ureter. In the renal sinus the three terminal branches break 

 up into numerous smaller branches, which penetrate the 

 kidney substance in the intervals between the renal papillae 

 (Fig. 1 8 1, p. 383). 



The renal artery gives a small branch the inferior suprarenal 



