Excretory System — Class 10 ICSE: 36 MCQs with answers

Carbon dioxide

Carbon dioxide is a respiratory waste product, not a nitrogenous one. Urea, ammonia, and uric acid all contain nitrogen.

Liver

Urea is formed in the liver by deamination of excess amino acids. The kidney only removes it.

Nephron

The nephron is the functional unit of the kidney; each kidney contains about a million of them.

Ureter

Ureters are two narrow tubes that carry urine from each kidney to the bladder by peristalsis.

True

Urea is formed in the liver by deamination of excess amino acids — not in the kidney.

Urea

Urea is the main nitrogenous waste product removed by the kidneys, formed from the deamination of excess amino acids in the liver.

Lungs

The lungs are responsible for excreting carbon dioxide, a respiratory waste product.

Nephron

The nephron is the functional unit of the kidney, responsible for urine formation.

Glucose

Glucose is not typically found in healthy urine because it is reabsorbed back into the blood during urine formation.

Ultrafiltration

Ultrafiltration occurs in the glomerulus, where blood is filtered under high pressure to form glomerular filtrate.

Controlling water and salt balance

The primary role of the kidneys in osmoregulation is to control the water and salt balance of the body.

Ureter

The ureter is the tube that carries urine from the kidney to the urinary bladder.

Increases water reabsorption

ADH increases water reabsorption in the collecting duct, leading to more concentrated urine.

Liver

The liver produces bile pigments, which are then excreted via the intestines.

To remove waste products

The main purpose of the excretory system is to remove waste products from the body to prevent toxicity.

Urea

Urea is the primary nitrogenous waste product removed by the kidneys, formed from the deamination of excess amino acids in the liver.

Lungs

The lungs are responsible for excreting carbon dioxide, which is a respiratory waste product.

Nephron

The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine.

Liver

Urea is formed in the liver through the process of deamination of excess amino acids.

To remove waste

The primary function of the excretory system is to remove harmful waste products from the body.

Ureter

The ureter is the structure that carries urine from the kidney to the urinary bladder.

Excretes water and salts

The skin, through sweat glands, excretes water, salts, and tiny amounts of urea.

Ultrafiltration

Ultrafiltration is the process that occurs in the glomerulus of the nephron where blood is filtered.

Urea

Urea is a nitrogenous waste product formed from the breakdown of proteins in the liver.

To control water reabsorption

ADH (antidiuretic hormone) controls the reabsorption of water in the collecting duct of the nephron.

The kidney filters everything small, then reabsorbs useful substances

Ultrafiltration removes all small molecules; selective reabsorption then returns glucose, amino acids, most water, and some salts to the blood.

Both A and R are true, and R correctly explains A

More protein means more excess amino acids, which the liver deaminates to produce more urea — so R directly explains A.

More water is reabsorbed, producing concentrated urine

ADH makes the collecting duct reabsorb more water, so a smaller amount of concentrated urine is produced.

Kidney → ureter → bladder → urethra

Urine flows from the kidney through the ureter into the urinary bladder, then out through the urethra.

Lungs

The lungs excrete respiratory waste (CO₂ and water vapour), while the others excrete nitrogenous waste, salts, water, or bile pigments.

Blood cells and large proteins

Large proteins and blood cells are too big to pass through the glomerulus, so they stay in the blood.

Uremia

Uremia is the accumulation of urea in the blood due to kidney failure.

The dialysing fluid has no urea but has normal glucose concentration

The dialysing fluid has the same glucose and salt concentration as blood but no urea, so only urea diffuses out down its concentration gradient.

Large volume of dilute urine

Excess water lowers ADH, so less water is reabsorbed and a large amount of dilute urine is produced.

Production of bile pigments

Bile pigments are produced by the liver from broken-down haemoglobin, not by the kidney.

I, II and III are all correct

All three statements correctly describe the three steps of urine formation: ultrafiltration, selective reabsorption, and tubular secretion.