ICSE Class 10 Biology: Excretory System — Important Questions with Answers 2026

Short Answer Questions (2-3 Marks)

• Q: Draw a neat labelled diagram of the human excretory system.
  Ans: The human excretory system consists of: Two kidneys (bean-shaped, in the abdominal cavity), two ureters (tubes from kidneys to bladder), urinary bladder (stores urine), urethra (tube for urine discharge). Right kidney is slightly lower than left. Each kidney has about 1 million nephrons.
• Q: Describe the structure of a nephron.
  Ans: A nephron is the structural and functional unit of the kidney. Parts: (1) Bowman's capsule — cup-shaped, contains glomerulus. (2) Glomerulus — tuft of capillaries (branch of renal artery). (3) Proximal Convoluted Tubule (PCT) — highly coiled, for reabsorption. (4) Loop of Henle — U-shaped, descending and ascending limbs. (5) Distal Convoluted Tubule (DCT) — for secretion. (6) Collecting duct — collects from many nephrons.
• Q: Describe the process of urine formation.
  Ans: Three steps: (1) Ultrafiltration (in glomerulus): Blood is filtered under pressure. Small molecules (water, glucose, amino acids, urea, salts) pass into Bowman's capsule as glomerular filtrate. Large molecules (proteins, blood cells) retained. (2) Selective reabsorption (in PCT): Useful substances (glucose, amino acids, water, some salts) reabsorbed into blood. (3) Tubular secretion (in DCT): Additional waste (H⁺, K⁺, creatinine) secreted from blood into tubule. Final product: urine.

Long Answer / Application Questions (4-6 Marks)

• Q: What is dialysis? When is it needed?
  Ans: Dialysis (haemodialysis) is the artificial process of removing waste products and excess water from the blood when kidneys fail. The patient's blood is passed through a dialyser (artificial kidney) containing a semi-permeable membrane. Waste products diffuse out into the dialysis fluid. Clean blood is returned to the body. Needed when kidneys are damaged (kidney failure) and cannot filter blood properly.

Exam Tips for This Chapter

• Revise all definitions and laws from Excretory System — they are commonly asked as 1-2 mark questions
• Practice diagrams related to Excretory System — neat labelled diagrams carry 2-3 marks
• For numericals, always show formula → substitution → answer with correct units
• Previous year analysis shows Excretory System carries 8-12 marks in the board exam