BiologyICSE Class 10 · Excretory System

The Human Urinary System and the Structure of the Kidney (ICSE Class 10 Biology)

Updated 16 October 2026 · Fact-checked

The human urinary system has two bean-shaped kidneys that filter blood and form urine, two ureters that carry it by peristalsis, a urinary bladder that stores it, and a urethra through which it leaves. The renal artery brings blood in and the renal vein takes it out. A kidney section shows cortex, medulla with pyramids, and pelvis.

Understand Human Urinary System and Structure of the Kidney

Excretion first. Excretion is the removal of metabolic wastes, especially nitrogenous wastes such as urea, from the body. It differs from egestion (defecation), which removes undigested food that never entered body cells, and from secretion, which releases useful substances such as enzymes. Urea is formed in the liver from excess amino acids and carried by blood to the kidneys.

Excretory organs (a brief idea).

Organ	Excretes
Kidneys	urea, excess water and salts, as urine
Lungs	carbon dioxide and water vapour
Skin	water, salts, a little urea, as sweat
Liver	bile pigments (from broken-down haemoglobin) via the intestine; forms urea

Parts of the urinary system and their functions.

Part	Description	Function
Kidneys (2)	dark red, bean-shaped, on the back wall of the abdomen on either side of the backbone; right slightly lower than left	filter blood, form urine, regulate water and salt balance
Renal artery	branch of the dorsal aorta	brings oxygenated blood containing wastes into the kidney
Renal vein	joins the inferior vena cava	takes filtered blood away
Ureters (2)	narrow muscular tubes from the hilum	carry urine to the bladder by peristalsis
Urinary bladder	muscular, elastic bag in the pelvic region	stores urine
Urethra	tube from the bladder to the outside, with sphincter muscles	passes urine out

Hilum. The notch on the inner, concave side of each kidney where the renal artery enters and the renal vein and ureter leave.

Internal structure of the kidney (longitudinal section).

Capsule: thin, tough outer covering.
Cortex: outer, darker, granular region with the Malpighian capsules and convoluted tubules.
Medulla: inner, paler region with cone-shaped renal pyramids (loops of Henle and collecting ducts); their tips (papillae) point into the pelvis.
Pelvis: funnel-shaped space collecting urine and leading into the ureter.

Micturition. The passing out of urine from the urinary bladder through the urethra. As the bladder fills, stretch receptors signal the need; the muscular bladder wall contracts and the sphincter muscles around the urethra relax. In adults this is under voluntary control; in infants it is a reflex.

Flow chart: path of urine. Nephrons (cortex and medulla) → collecting ducts → pyramids → pelvis → ureter → urinary bladder → urethra → outside.

Draw-and-label checklist: urinary system (emphasis on correct labels). Two kidneys at the same level near the backbone (the right slightly lower); dorsal aorta on one side and inferior vena cava on the other, both vertical; renal artery from the aorta and renal vein to the vena cava, kept separate; ureters running down to the bladder; urethra below. Labels: kidney, renal artery, renal vein, dorsal aorta, inferior vena cava, ureter, urinary bladder, sphincter, urethra.

Draw-and-label checklist: L.S. of kidney. Bean outline with capsule; darker cortex band; pyramids in the medulla pointing inwards; pelvis leading into the ureter; renal artery and vein at the hilum.

Human Urinary System and Structure of the Kidney: key facts

Parts and functions: Kidney forms urine
Ureter carries urine by peristalsis
Bladder stores urine
Urethra passes urine out
Sphincter controls opening; One function per part.
Kidney section: Capsule covering
Cortex Malpighian capsules
Medulla pyramids
Pelvis collects urine, leads to ureter; Outer to inner.
Excretory organs: Kidneys urea, water, salts
Lungs CO₂, water vapour
Skin sweat
Liver bile pigments, forms urea; Urea is a substance; urine is the liquid.

Kidney	forms urine
Ureter	carries urine by peristalsis
Bladder	stores urine
Urethra	passes urine out
Sphincter	controls opening

Capsule	covering
Cortex	Malpighian capsules
Medulla	pyramids
Pelvis	collects urine, leads to ureter

Kidneys	urea, water, salts
Lungs	CO₂, water vapour
Skin	sweat
Liver	bile pigments, forms urea

How to answer Human Urinary System and Structure of the Kidney questions

ICSE asks you to define excretion or micturition, draw and label the urinary system or kidney section, give functions of its parts, and name the vessels of the kidney.

1For excretion, say 'removal of nitrogenous (metabolic) wastes such as urea'.
2For micturition, name the bladder, urethra and sphincter muscles.
3In diagrams, keep the renal artery joined to the aorta and the renal vein to the vena cava.
4Label the kidney section from outside in: capsule, cortex, medulla (pyramids), pelvis.
5Write urea, not urine, when a nitrogenous waste is asked.

Human Urinary System and Structure of the Kidney in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Holding urine on a long bus ride

Suppose on a four-hour bus journey with no stops a student feels a strong urge to pass urine but manages to wait until the bus halts.

Which structures allow this, and what happens when he finally passes urine?

Try it first, then show the solutionSolution

Urine trickles constantly from the kidneys down the ureters into the bladder.
The elastic bladder stretches to store it; stretch signals create the urge.
The sphincter muscles around the urethra stay contracted under voluntary control, holding urine in.
At the halt, the bladder wall contracts and the sphincters relax: micturition.

Answer: The elastic bladder stores urine and voluntary sphincters keep the urethra closed until micturition.

Memory hook: Bladder stores, sphincter guards.

Kidney stone pain

Suppose a man feels sharp pain in his side spreading towards the groin, and a scan shows a small stone stuck in a narrow tube leaving the kidney.

Name the tube and explain the pain.

Try it first, then show the solutionSolution

The tube leaving the kidney's pelvis is the ureter.
Its muscular wall pushes urine down by peristalsis.
A stone blocks the narrow ureter, so the muscles contract hard against it.
Urine backs up into the kidney, causing pain along the ureter's path.

Answer: The ureter; strong peristaltic contractions against the blockage cause pain.

Memory hook: Ureter = U-tube to the bladder.

Tricks to remember Human Urinary System and Structure of the Kidney

Short memory aids. Say each one aloud once, then use it on a question the same day.

K-U-B-U
Kidney, Ureter, Bladder, Urethra: the path from top to bottom.
Use it when: Order of urinary organs.
UreTER before UreTHRA
Ureter has the E before; urethra exits last.
Use it when: Not confusing ureter and urethra.
Excretion vs egestion
Excretion = made inside cells; Egestion = Eaten but never absorbed.
Use it when: Defining excretion correctly.

Human Urinary System and Structure of the Kidney: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Storage organ · 1 mark · MCQBoard level

The organ that stores urine until it is passed out is the:
(a) ureter (b) kidney (c) urinary bladder (d) urethra

Try it first, then show the solutionSolution

The muscular, elastic urinary bladder stores urine.

Answer: (c) urinary bladder.

Example 2: What is micturition? · 1 mark · Very short answerBoard level

A student writes, 'Micturition is the removal of wastes from the body.' Correct this definition. (Micturition was asked in 2025.)

Try it first, then show the solutionSolution

Name the organ, the passage and the muscles involved.

Answer: Micturition is the expulsion of urine from the urinary bladder through the urethra, by contraction of the bladder wall and relaxation of the sphincter muscles.

Example 3: Excretion, egestion, secretion · 2 marks · Short answerHarder board level

Classify each as excretion, egestion or secretion, giving a reason: (a) bile pigments leaving the body with faeces; (b) undigested cellulose in faeces; (c) saliva poured into the mouth; (d) carbon dioxide breathed out.

Try it first, then show the solutionSolution

(a) Excretion: bile pigments are metabolic wastes made in the body from broken-down haemoglobin; (b) egestion: cellulose was never digested or absorbed into cells (1 mark).
(c) Secretion: saliva is a useful substance released by glands; (d) excretion: CO₂ is a metabolic waste of cell respiration (1 mark).

Answer: (a) Excretion (b) Egestion (c) Secretion (d) Excretion.

Example 4: Tracing a drop of urine · 3 marks · Short answerHarder board level

A drop of urine forms in a nephron whose Malpighian capsule lies near the outer edge of the kidney. Trace its path out of the kidney, naming in order the kidney regions it passes through, and state what each region contains.

Try it first, then show the solutionSolution

It forms in the cortex, the outer granular region containing Malpighian capsules and convoluted tubules (1 mark).
It passes through the medulla, in a renal pyramid containing loops of Henle and collecting ducts, and drips from the tip of the pyramid (1 mark).
It collects in the pelvis, the funnel-shaped space that leads into the ureter (1 mark).

Answer: Cortex (Malpighian capsules, convoluted tubules) → medulla, renal pyramid (loops of Henle, collecting ducts) → pelvis → ureter.

Example 5: Bladder timing · 3 marks · Case-basedHOTS / competency

Suppose urine reaches the bladder at about 50 mL per hour and the urge to pass urine is strong when it holds about 400 mL. (a) After how many hours would the urge become strong? (b) Name the tubes that carry urine to the bladder and how they move it. (c) Why does urine not flow back up these tubes when the bladder contracts?

Try it first, then show the solutionSolution

(a) 400 ÷ 50 = 8 hours (1 mark).
(b) Ureters, by peristalsis of their muscular walls (1 mark).
(c) The ureters enter the bladder at a slant, so bladder pressure squeezes their openings shut (and peristalsis keeps pushing downwards) (1 mark).

Answer: (a) 8 hours. (b) Ureters, by peristalsis. (c) The slanting entry closes under bladder pressure.

Example 6: Diagram error spotter · 3 marks · Short answerHOTS / competency

Suppose in a student's diagram of the urinary system the renal vein is drawn joining the dorsal aorta and the renal artery joining the inferior vena cava. Explain the errors and state the correct connections, including the type of blood each vessel carries.

Try it first, then show the solutionSolution

The renal artery is a branch of the dorsal aorta, not the vena cava (1 mark).
The renal vein opens into the inferior vena cava, not the aorta (1 mark).
Renal artery: oxygenated blood rich in urea; renal vein: deoxygenated, filtered blood with little urea (1 mark).

Answer: Swap them: artery from aorta (oxygenated, urea-rich), vein to vena cava (deoxygenated, filtered).

Where students lose marks in Human Urinary System and Structure of the Kidney

The slips examiners see most often, and what to write instead.

Mistake: Micturition as 'removal of wastes'
CISCE examiners' comments (2025): candidates wrote only 'passing urine' without the role of the urinary bladder and sphincter muscles, or 'removal of wastes from the body'.
Do this: Bladder contracts, sphincters relax, urine leaves through the urethra.
Usually costs: 1 mark.
Mistake: Excretion confused with egestion
CISCE examiners' comments (2025): candidates confused excretion with egestion and defecation and did not specify nitrogenous waste.
Do this: Excretion = removal of nitrogenous (metabolic) waste such as urea.
Usually costs: 1 mark.
Mistake: Urine for urea
CISCE examiners' comments (2024): asked for a nitrogenous waste, candidates wrote urine instead of urea.
Do this: Urea is the waste; urine carries it.
Usually costs: 1 mark.

Exam tips

Kidney → ureter → bladder → urethra.
Renal artery from aorta; renal vein to inferior vena cava.
Kidney section: capsule, cortex, medulla with pyramids, pelvis.
Micturition: bladder, urethra, sphincters.

Practice questions on Human Urinary System and Structure of the Kidney

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Urine is carried from the kidneys to the bladder by the:
(a) urethra (b) ureters (c) renal veins (d) collecting ducts
Hint
Two tubes.
Answer
(b) ureters.
Q2 · 1 mark · Very short answerBoard level
Name the main nitrogenous waste excreted by the kidneys.
Hint
Substance, not liquid.
Answer
Urea.
Q3 · 1 mark · Very short answerHarder board level
Name the organ that forms urea in the body.
Hint
From excess amino acids.
Answer
Liver.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): The lungs are excretory organs.
Reason (R): The lungs remove carbon dioxide produced by respiration in cells.
(a) (A) is true and (R) is false.
(b) (A) is false and (R) is true.
(c) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(d) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
Hint
Metabolic waste.
Answer
(c).
Q5 · 2 marks · Short answerHarder board level
What is the hilum of the kidney? Name the structures passing through it.
Hint
Notch.
Answer
The notch on the concave inner side of the kidney; the renal artery enters and the renal vein and ureter leave there.
Q6 · 1 mark · Very short answerHarder board level
Why can an adult hold urine for some time while an infant cannot?
Hint
Voluntary or reflex?
Answer
In adults the sphincter muscles of the urethra are under voluntary control and can be kept contracted; in infants micturition is a reflex, so the bladder empties when it fills.
Q7 · 2 marks · Short answerHarder board level
List the excretory products removed by (a) skin, (b) liver.
Hint
Sweat; bile.
Answer
(a) Water, salts and a little urea in sweat. (b) Bile pigments from broken-down haemoglobin, passed out through the intestine.
Q8 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a healthy man donates one of his kidneys to his brother, whose kidneys have failed.
(a) Besides the renal vein, which blood vessel and which tube must the surgeon connect to the transplanted kidney? (1)
(b) Why can the donor live normally with one kidney? (1)
(c) Which nitrogenous waste would build up in the brother's blood if the new kidney failed? (1)
Hint
One vessel in, one tube out.
Answer
(a) The renal artery and the ureter. (b) One kidney has enough nephrons to filter all the blood and regulate water and salts. (c) Urea.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What moves urine down the ureters?Show answer
Peristalsis.
2.Which region of the kidney contains the pyramids?Show answer
Medulla.
3.What is excretion?Show answer
Removal of metabolic, mainly nitrogenous, wastes from the body.
4.Which kidney lies slightly lower?Show answer
The right kidney.
5.Where does the renal vein drain?Show answer
Into the inferior vena cava.

Human Urinary System and Structure of the Kidney: frequently asked questions

Why is the right kidney lower?

The large liver lies above it on the right side.

Is sweating excretion?

Partly. Sweat removes water, salts and a little urea, though its main role is cooling.

Is micturition voluntary?

In adults the urethral sphincter is under voluntary control; in infants it is a reflex.

Do I need adrenal glands on the kidney diagram?

They sit on top of the kidneys but belong to the endocrine system; label them only if asked.