GROSS ANATOMY 25 



Some investigators have considered it as capable of blocking 

 the blood leaving the adrenal. It is more likely, however, that 

 this muscular development acts to help propel the venous 

 blood into the caval system thereby ensuring the circulation 

 of the vital products of the adrenal gland. 



The adrenal vein receives the blood from the medullary 

 venous plexus and from the cortex. It emerges from the 

 hilum of the gland and opens on the right into the inferior vena 

 cava and on the left into the renal vein. 



Under certain conditions, the venous blood from the adrenals 

 reaches the portal vein. According to Cow 131 part of the blood 

 supply to the medulla in the cat goes to the kidney. In the 

 dog this venous anastomosis of adrenal and renal vessels occurs 

 only rarely. 



The efferent blood vessels of the adrenals are divided by 

 Ferguson 194 into four types: the sinusoids, the small central 

 vein, the large central vein, and the suprarenal vein. Each 

 of these types presents distinctive features but in all of them 

 circular muscle is conspicuously deficient or absent. The 

 large central vein is characterized by prominent and charac- 

 teristic muscular ridges. 



Lymphatics. The lymphatics of the adrenals run in the 

 trabeculae of the cortex and are connected with spaces between 

 the trabeculae and the cell columns and by clefts between the 

 cells within the columns. They communicate with efferent- 

 valved lymphatics in the fibrous capsule and in the medulla 

 where they form a close plexus around the central vein. The 

 lymphatics of the adrenals drain into the lateral aortic lymph 

 glands. 



Nerve supply. The adrenals receive their chief innervation 

 from the splanchnics. It is questionable if twigs from the vagi 

 and phrenics also innervate the adrenals, as some writers claim. 

 In the rabbit the right adrenal is supplied by both right and 

 left splanchnics while the left gland receives fibers from the 

 right splanchnic only. The fibers to the adrenals are derived 



