# Excretory Products and their Elimination Notes | SwaVid Excretory Products and their Elimination, NCERT Class 11 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/biology/chapter/excretory-products-and-their-elimination Source: https://www.swavid.com/cbse/class-11/biology/chapter/excretory-products-and-their-elimination # Excretory Products and their Elimination ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Biology on SwaVid ### Modes of excretion ### Human excretory system and nephron ### Urine formation ### Counter current mechanism ### Regulation of kidney function ### Other excretory organs and disorders ### Next chapter ### Related chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Biology › Excretory Products and their Elimination Notes written by SwaVid from the NCERT textbook. Class 11 Biology, Chapter 16. Key ideas, formulas and common mistakes. CBSE prints 18 marks for Unit V, not for this chapter alone. Short answer. This chapter describes how animals remove nitrogenous wastes like ammonia, urea, and uric acid, focusing on the human excretory system. It explains the structure of the nephron, urine formation, concentration mechanisms, regulation, and disorders of excretion. Source: NCERT Biology (Reprint 2026-27) , Chapter 16, Excretory Products and their Elimination Animals eliminate nitrogenous wastes primarily as ammonia, urea, or uric acid based on water availability. Ammonotelism requires large amounts of water, ureotelism converts ammonia to less toxic urea in the liver, and uricotelism conserves the most water by excreting uric acid as paste or pellets. The human excretory system consists of a pair of kidneys, ureters, a urinary bladder, and a urethra. Each kidney contains around one million nephrons, which are the structural and functional units composed of a glomerulus and a long renal tubule. Urine formation involves glomerular filtration, tubular reabsorption, and tubular secretion. Podocytes form filtration slits over the glomerular capillaries, and nearly 99 percent of the filtrate is reabsorbed by active and passive transport along the renal tubules. Henle's loop and the vasa recta maintain an increasing osmolarity gradient from the cortex (300 mOsmol L⁻¹) to the inner medulla (1200 mOsmol L⁻¹). This counter current system facilitates significant water reabsorption from the collecting duct, producing concentrated urine. Kidney function is regulated by feedback mechanisms involving the hypothalamus, the juxtaglomerular apparatus (JGA), and the heart. Antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system increase water retention and blood pressure, whereas atrial natriuretic factor (ANF) acts as a check by promoting vasodilation. Lungs, liver, and skin assist in the elimination of carbon dioxide, bile pigments, and sweat salts. Malfunctions cause uremia, which can be treated by hemodialysis or renal transplantation, while other disorders include renal calculi and glomerulonephritis. Try each question first. Then tap it to see the answer. Filtrate formed per hour = 125 mL × 60 = 7500 mL Filtrate formed per day = 7500 mL × 24 = 180000 mL Convert to litres = 180000 / 1000 = 180 litres 180 L Reabsorbed volume = 180 L - 1.5 L = 178.5 L Percentage reabsorbed = (178.5 / 180) × 100 Percentage reabsorbed = 99.17% 99.17% Volume filtered = (1 / 5) × Cardiac output Volume filtered = (1 / 5) × 5500 mL Volume filtered = 1100 mL 1100 mL Locomotion and Movement . Body Fluids and Circulation . Chemical Coordination and Integration . Breathing and Exchange of Gases . The 19 chapters of Class 11 Biology . CBSE does not give marks to one chapter. It prints 18 marks for Unit V, Human Physiology, which includes Excretory Products and their Elimination. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Locomotion and Movement. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 16 NCERT book - 18 marks, Unit V - 3 quick checks - Confusing the permeability of the descending and ascending limbs of Henle's loop . Remember that the descending limb allows water to leave and keeps salts in, while the ascending limb is strictly impermeable to water and transports salts out. - Assuming hemodialysis fluid contains urea to maintain osmotic balance . Dialysing fluid has the exact composition of normal plasma except that it completely lacks nitrogenous wastes, allowing urea to diffuse out of blood down its concentration gradient. - Believing antidiuretic hormone decreases blood pressure . ADH prevents diuresis and causes vasoconstriction, which actually increases blood pressure and aids glomerular filtration. - Thinking that all nephrons possess long loops of Henle dipping into the inner medulla . Only juxtamedullary nephrons have long loops running deep into the medulla; the majority are cortical nephrons with very short loops extending only slightly into the medulla. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 19 chapters](https://www.swavid.com/cbse/class-11/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/locomotion-and-movement) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/body-fluids-and-circulation) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/chemical-coordination-and-integration) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/breathing-and-exchange-of-gases) - [Class 11 Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup)