The basic functional unit of the kidney is the

1. Analyze the question The question asks for the basic functional unit of the kidney. This means the smallest structure that can carry out all the kidney's functions (filtration, reabsorption and secretion) on its own.

2. Explain the concept The kidney is made up of about one million tiny tubular structures called nephrons. Each nephron is a complete working unit. It has these parts:

• Bowman's capsule: a cup-shaped structure that surrounds the glomerulus.
• Glomerulus: a knot of capillaries where ultrafiltration of blood takes place.
• Proximal convoluted tubule: reabsorbs glucose, amino acids, and most of the water and salts.
• Loop of Henle: creates a concentration gradient so water can be conserved.
• Distal convoluted tubule: fine-tunes salt and water balance.
• Collecting duct: carries urine to the pelvis of the kidney.

3. Work through the options

• A. Nephron: the whole functional unit, containing all the parts below. ✔
• B. Bowman's capsule: only one part of the nephron, which collects the filtrate.
• C. Glomerulus: only the capillary network where filtration happens.
• D. Loop of Henle: only the section that helps concentrate urine.

Options B, C and D are all parts of the nephron. Only the nephron as a whole performs the full job of making urine.

4. Answer The basic functional unit of the kidney is the nephron, which is option A.

5. Exam tip Remember the pattern: Neuron is the unit of the nervous system, and Nephron is the unit of the kidney. If an option is just a "part" of a structure and another option is the "whole" unit, the whole unit is usually the right answer when the question asks about the "basic unit".