Excretory Products And Their Elimination

Each kidney contains roughly one million nephrons, the functional units responsible for urine formation. According to NCERT Class 11, Chapter 19 (Excretory Products and their Elimination), the glomerulus, a tuft of capillaries, is enclosed within the cup-shaped Bowman's capsule, and together they constitute the Malpighian body or renal corpuscle, which is the site of ultrafiltration. Blood pressure within the glomerular capillaries forces water and small solutes across three filtration layers into the capsular space, producing the glomerular filtrate. The loop of Henle is concerned mainly with concentrating the filtrate by establishing a medullary osmotic gradient, not with the initial filtration. The collecting duct fine-tunes water reabsorption under hormonal control and conducts urine toward the pelvis, again downstream of filtration. The distal convoluted tubule performs selective secretion and reabsorption to regulate ionic and acid-base balance, but it does not carry out ultrafiltration. Hence the Malpighian body is correct. A process-order plausibility check confirms this: filtration must be the first step of urine formation, and only the glomerulus-Bowman's capsule combination is structured with a high-pressure capillary bed suited to that initial bulk filtration.