The renal hilum expands into a cavity within the kidneys called ______.

Correct option is B

Sol. The renal sinus is a cavity within the kidney that extends from the renal hilum. It contains the renal pelvis, calyces, blood vessels, nerves, and fat. It acts as a conduit for the passage of urine from the collecting ducts to the ureter. The renal sinus is essential in maintaining kidney structure and function, ensuring proper filtration and urine transport.
Explanation of each option:
· (a) Renal medulla – Incorrect. The renal medulla is the innermost part of the kidney, composed of renal pyramids, which contain nephron structures like loops of Henle and collecting ducts. It plays a crucial role in urine concentration by facilitating water reabsorption. Any dysfunction in the medulla can lead to issues like impaired urine concentration and electrolyte imbalance.
· (b) Renal sinus – Correct answer. It is the cavity within the kidney that extends from the hilum, housing important structures such as the renal pelvis and blood vessels. It serves as the main passage for filtrates and urine transport before exiting via the ureter. Damage to the renal sinus can lead to urinary obstruction and kidney dysfunction.
· (c) Renal cortex – Incorrect. The renal cortex is the outermost layer of the kidney, containing glomeruli, proximal tubules, and distal tubules, which are responsible for filtration and initial urine formation. It provides a crucial environment for nephrons to perform filtration and reabsorption processes. Damage to the renal cortex can lead to kidney diseases like acute glomerulonephritis and nephrotic syndrome.
· (d) Renal arteries – Incorrect. The renal arteries are responsible for supplying oxygenated blood to the kidneys, ensuring proper filtration of waste and electrolyte balance. They branch directly from the abdominal aorta and enter the kidneys through the renal hilum. Any blockage in the renal arteries can result in renal hypertension and reduced kidney function due to decreased blood supply.