ABDOMINAL CAVITY 541 



common iliacs, the single branches have already been described. 

 The middle sacral artery will be examined when the pelvis 

 is dissected. The paired branches may now be examined. 



Arteriae Phrenicae Inferiores (Inferior Phrenic Arteries). 

 These have already been noticed upon the under sur- 

 face of the diaphragm. They are two in number, and are 

 the first branches which spring from the abdominal aorta. 

 Diverging from each other, the artery of the right side passes 

 behind the inferior vena cava, whilst the artery of the left 

 side goes behind the oesophagus. Near the posterior border 

 of the central tendon of the diaphragm each divides into 

 a lateral and a medial branch. The lateral branch pro- 

 ceeds laterally to anastomose with the intercostal arteries, 

 whilst the medial branch curves forwards in front of the 

 central tendon, and ends by anastomosing with its fellow, 

 and with the terminal branches of the internal mammary 

 artery. Each phrenic artery, in addition to the branches 

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

 superior suprarenal artery r , to the suprarenal gland. On the left 

 side it also sends a few minute branches to the oesophagus. 



The phrenic veins open into the inferior vena cava. 



Arteriae Suprarenales Mediae (O.T. Middle Capsular 

 Arteries). The middle suprarenal arteries are two small 

 vessels which arise, one from each side of the aorta, at 

 the same level as the superior mesenteric. They run 

 laterally and upwards, in front of the crura of the diaphragm, 

 to the suprarenal glands, into the substance of which they 

 sink. On the right side the middle suprarenal artery 

 passes behind the inferior vena cava. They anastomose 

 freely with the superior and inferior capsular arteries. 



The right suprarenal vein opens into the inferior vena cava, 

 whilst the left vein ends in the renal or phrenic vein. 



Arteriae Renales (Renal Arteries). When compared with 

 the organs which they supply, the renal arteries are dispro- 

 portionately 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. Each artery proceeds laterally 

 at right angles to the aorta, and, approaching the kidney, 



