Final answer:
The renal hilum is the medial depression of a kidney, acting as the entry and exit point for structures like arteries, veins, nerves, lymphatics, and the ureter.
Step-by-step explanation:
The medial depression of a kidney is known as the renal hilum. This is the area on the medial side of each kidney where various structures such as the renal artery, renal vein, nerves, lymphatics, and particularly the ureter, enter and exit the kidney. The renal hilum is essentially the doorway that allows the renal pelvis to channel urine through to the ureter, and it also allows blood vessels and nerves to access the internal structures of the kidney. Ensuring that the kidneys are well-connected to the circulatory and nervous systems is crucial for their function in filtering blood and generating urine.