The functional unit of the kidney is the:

• A. Renal pelvis
• B. Ureter
• C. Cortex
• D. Nephron

Answer: (D)

Verified step by step guidance

1. Understand that the kidney is composed of several structures, each with specific functions. The renal pelvis is a funnel-shaped structure that collects urine, the ureter transports urine to the bladder, and the cortex is the outer layer of the kidney.
2. Recognize that the functional unit of the kidney is the smallest structure capable of performing all the kidney's functions, such as filtering blood and forming urine.
3. Identify the nephron as this functional unit, which consists of a renal corpuscle and a renal tubule, responsible for filtering blood, reabsorbing needed substances, and secreting waste into urine.
4. Recall that each kidney contains approximately one million nephrons, making them essential for the kidney's role in maintaining fluid and electrolyte balance.
5. Conclude that among the options given, the nephron is the correct answer because it is the microscopic structure that carries out the kidney's primary functions.