Biology

Class 11

Biology · Class 11 · Chapter 16

Excretory Products and their Elimination

13 lessons 89 min 2 simulations

This chapter is about how animals get rid of the wastes their metabolism piles up, above all the nitrogen-containing ones. It compares ammonia, urea and uric acid and the excretory organs of different animal groups, then works through the human kidney: the nephron, the three steps of urine formation, what each part of the tubule does, the counter current mechanism that concentrates urine, hormonal control by ADH, renin–angiotensin and ANF, micturition, the help given by lungs, liver and skin, and kidney disorders and their treatment.

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What the exam asks

NEET leans on the numbers (nearly one million nephrons per kidney, 1100–1200 mL of blood filtered per minute, GFR 125 mL/min or 180 L/day, about 99 per cent reabsorbed, 300 to 1200 mOsmol L⁻¹, urine about four times concentrated, 1–1.5 L urine and 25–30 g urea a day, pH 6.0), on which animals are ammonotelic, ureotelic or uricotelic, and on the permeability of the two limbs of Henle's loop. Marks are lost by swapping the permeabilities of the descending and ascending limbs, by mixing up what ADH, renin–angiotensin and ANF each do, and by placing the loop of Henle in the cortex.

Lessons

13 lessons · 89 min