The blood supply of the mammalian adrenal medulla: a comparative study.

Adrenal medullary arteries have been followed from their origins in the capsular or subcapsular plexus to the medullary plexus in the mouse, rat, hamster, cat, guinea-pig, rabbit and bovine. Adrenal medullary arteries have a zonal distribution to the medullary capillary plexus and the number of arteries present in species variable and proportional to the size of the medulla. Cortical veins drain through distinct venous channels between groups of chromaffin cells, and may run adjacent to either adrenaline-storing (A) or noradrenaline-storing (NA) cells. In the normal unstimulated gland both A and NA cells lie adjacent to capillaries of the medullary plexus which derive their blood supply from adrenal medullary arteries. In the normal unstimulated gland no evidence of selective supply of arterial or venous blood to either A or NA cells has been obtained.