Which area of the kidney is known as the outer dark region?

The cortex of the kidney is known as the outer dark region due to its distinct structure and composition. This area contains a high concentration of renal corpuscles and convoluted tubules, which contribute to its darker appearance compared to the medulla. The cortex plays a crucial role in filtering blood and is where the initial stages of urine formation occur.

In contrast, the medulla, which lies beneath the cortex, consists primarily of the renal pyramids and is responsible for concentrating urine. The pelvis is the central collecting region of the kidney and does not have a dark appearance, as it is a funnel-like structure that collects urine before it moves to the ureter. The collecting duct, found within both the cortex and medulla, is important for water reabsorption and urine concentration but does not define the dark outer region of the kidney. Thus, the cortex is correctly identified as the outer dark region of the kidney due to its anatomical and functional characteristics.