Illustration of the male perineal cavity. The bladder (yellow), prostate (blue), pelvic floor (pink on the left), the rectum behind the bladder and spine are all visible. The aorta descends in front of the lumbar vertebra (L4) and divides into the two iliac arteries. Each primitive iliac artery leads to an external iliac artery which vascularises the lower member, and an internal artery which vascularises organs in the perineum. The iliac vein follows the same path as the iliac artery. The external iliac lymph nodes, the ilio-obturator lymph nodes and the lymph nodes of the promontory are also visible.