Correct Option
The correct option is
Both A and R are true but R is NOT the correct explanation of A
.Explanation
The kidney is the primary organ of the excretory system in humans, responsible for maintaining homeostasis by filtering blood and producing urine. The fundamental component responsible for these activities is the nephron.
Assertion and Reason Analysis
- Assertion (A): Correct. The nephron is defined as the structural and functional unit of the kidney. Structurally, each kidney is composed of approximately one million nephrons. Functionally, each nephron independently performs the essential tasks of the kidney, such as filtering blood and regulating chemical concentrations.
- Reason (R): Correct. Urine formation is a complex physiological process that involves three main steps:
- Glomerular Filtration: The filtration of blood in the glomerulus.
- Tubular Reabsorption: The absorption of essential substances (glucose, amino acids, water) back into the blood.
- Tubular Secretion: The secretion of waste ions (K+, H+) into the filtrate.
- Relationship: While both statements are factually true, the Reason does not correctly explain the Assertion. The Reason lists the processes involved in urine formation but does not explain why the nephron is considered the structural and functional unit. The nephron is the unit because it is the smallest structure capable of performing these processes, but the mere listing of the processes (R) is not the justification for the definition of the unit (A).
Key Takeaway: The nephron is the basic structural and functional unit of the kidney, where the processes of glomerular filtration, tubular reabsorption, and tubular secretion occur to form urine.