A notch present towards the centre of the inner concave surface of the kidney through which ureter, blood vessels and nerves enter is known as:

Hilum.

The correct answer is Option (3)-Hilum.

In humans, the excretory system consists of a pair of kidneys, one pair of ureters, a urinary bladder and a urethra . Kidneys are reddish brown, bean shaped structures situated between the levels of last thoracic and third lumbar vertebra close to the dorsal inner wall of the abdominal cavity. Each kidney of an adult human measures 10-12 cm in length, 5-7 cm in width, 2-3 cm in thickness with an average weight of 120- 170 g. Towards the centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter. Inner to the hilum is a broad funnel shaped space called the renal pelvis with projections called calyces. The outer layer of kidney is a tough capsule. Inside the kidney, there are two zones, an outer cortex and an inner medulla.