ScienceCBSE Class 10 · How do Organisms Reproduce?

Human Reproductive System

Updated 14 October 2026 · Fact-checked

Humans reproduce sexually. In males, the testes make sperms and testosterone; the vas deferens and urethra carry the sperms. In females, an ovary releases one egg a month into the oviduct, where fertilisation may occur. The embryo implants in the uterus and is fed through the placenta; an unfertilised egg leads to menstruation.

Understand Human Reproductive System

Puberty. Body growth continues from childhood, but in the early teenage years a different set of changes begins, as reproductive tissues mature once general growth starts to slow. This period of adolescence is puberty. Some changes are common to boys and girls: thick hair in the armpits and genital area, thinner hair on arms, legs and face, oily skin and pimples. Others differ: in girls, breast size increases, the skin of the nipples darkens and menstruation begins; in boys, thick facial hair appears and the voice begins to crack. These changes happen slowly, over months and years, at different ages in different people. Many of them signal that sexual maturation is taking place.

Male reproductive system. It has parts that make germ cells and parts that deliver them.

Testes produce sperms. They lie outside the abdominal cavity in the scrotum, because sperm formation needs a temperature lower than normal body temperature. The testes also secrete testosterone, which regulates sperm formation and brings about the changes of puberty in boys.
Sperms travel through the vas deferens, which joins a tube from the urinary bladder. The urethra is thus a common passage for sperms and urine.
Along the way, the prostate gland and seminal vesicles add secretions. The fluid makes transport of sperms easier and also provides nutrition.
A sperm is a tiny cell made mainly of genetic material, with a long tail to move towards the female germ cell.

Female reproductive system.

The ovaries make eggs (female germ cells) and some hormones. At birth they already contain thousands of immature eggs; from puberty some mature, and one egg is released each month by one of the ovaries.
The egg is carried through a thin oviduct (fallopian tube). The two oviducts join the uterus, an elastic, bag-like organ, which opens into the vagina through the cervix.

Fertilisation and development. Sperms entering the vagina during intercourse travel up and may meet the egg in the oviduct, where fertilisation occurs. The zygote divides to form a ball of cells, the embryo, which is implanted in the lining of the uterus and continues to grow, developing organs to become a foetus. Each month the uterus prepares for this: its lining thickens and gets a rich blood supply.

The placenta. The embryo gets nutrition from the mother's blood through the placenta, a disc embedded in the uterine wall. It has villi on the embryo's side and blood spaces on the mother's side surrounding the villi. This gives a large surface area for glucose and oxygen to pass from mother to embryo, and wastes from the embryo pass into the mother's blood. Development takes about nine months, and the baby is born by rhythmic contractions of the uterine muscles.

Menstruation. If the egg is not fertilised, it lives for about one day. The thick, spongy uterine lining prepared to nourish an embryo is not needed, so it slowly breaks down and leaves through the vagina as blood and mucus. This happens roughly every month and usually lasts about two to eight days.

Human Reproductive System: formulas and key facts

Path of sperms: $testes \to vas deferens \to urethra$; Prostate and seminal vesicles add fluid on the way.
Path of the egg: $ovary \to oviduct (fertilisation) \to uterus (implantation)$; Uterus opens into the vagina through the cervix.
Placenta exchange: $mother \to embryo: glucose, O_{2}; embryo \to mother: wastes$; Villi give a large surface area.
Monthly cycle: $1 egg per month; egg lives \approx 1 day; menstruation 2 to 8 days$; Uterine lining shed if no fertilisation.

How to solve Human Reproductive System questions

Questions on this topic ask for functions, pathways and reasons. Use this approach.

1For functions, pair each organ with its job: testes (sperms, testosterone), vas deferens (carries sperms), prostate and seminal vesicles (fluid for transport and nutrition), ovaries (eggs, hormones), oviduct (site of fertilisation), uterus (implantation, development).
2For pathways, list organs in order with arrows.
3For 'why' questions, give the reason in one line: scrotum for lower temperature; placenta villi for large surface area; menstruation because the prepared lining is not needed.
4For diagrams, label the organs from the NCERT figures and show the pathway with arrows.
5Keep answers factual and use correct biological terms.

Human Reproductive System in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Placenta as an exchange surface

Suppose your aunt is expecting a baby and your younger cousin asks how the baby 'eats and breathes' inside the mother when it cannot take food by mouth or breathe air.

Explain how the developing baby receives food and oxygen and gets rid of wastes, naming the structure involved and the feature that makes it efficient.

Try it first, then show the solutionSolution

The embryo is implanted in the thick, blood-rich lining of the uterus.
It is connected to the mother through the placenta, a disc embedded in the uterine wall.
On the embryo's side the placenta has villi; on the mother's side are blood spaces surrounding the villi, giving a large surface area.
Glucose and oxygen pass from the mother's blood to the embryo across this surface, and wastes from the embryo pass into the mother's blood to be removed.

Answer: Through the placenta: villi on the embryo's side and blood spaces on the mother's side give a large surface for glucose and oxygen to reach the baby and for wastes to pass to the mother's blood.

Memory hook: The placenta is the baby's lungs, stomach and kidneys rolled into one exchange disc.

Tricks to remember Human Reproductive System

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

T-V-U with a Pit stop
Testes → Vas deferens → Urethra, with a Pit stop where the Prostate and seminal vesicles add fluid.
Use it when: Ordering the male pathway.
O-O-U-C-V
Ovary, Oviduct, Uterus, Cervix, Vagina.
Use it when: Ordering the female organs.
Cool sperms
Scrotum outside the body = cooler, as sperm formation needs a lower temperature.
Use it when: Why testes are outside the abdomen.

Human Reproductive System: solved examples

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

Example 1: Functions of the testes · 2 marks · Very short answerBoard level

What are the functions of the testes in human beings? Why are they located in the scrotum?

Try it first, then show the solutionSolution

Testes produce sperms and secrete testosterone, which regulates sperm formation and brings about puberty changes in boys (1 mark).
They lie outside the abdominal cavity in the scrotum because sperm formation requires a temperature lower than normal body temperature (1 mark).

Answer: Sperm and testosterone production; scrotum keeps them at a lower temperature.

Example 2: Prostate and seminal vesicles · 2 marks · Very short answerBoard level

What is the role of the seminal vesicles and the prostate gland? Why is the urethra described as a common passage?

Try it first, then show the solutionSolution

They add secretions to the sperms so that the sperms are in a fluid that makes their transport easier and provides nutrition (1 mark).
The vas deferens joins a tube from the urinary bladder, so the urethra carries both sperms and urine (1 mark).

Answer: Fluid for transport and nutrition; urethra carries both urine and sperms.

Example 3: Nourishing the embryo · 3 marks · Short answerHarder board level

How does the embryo get nourishment inside the mother's body? Describe the structure of the placenta and explain how its design suits its function.

Try it first, then show the solutionSolution

The embryo implants in the uterine lining, which is thickened and richly supplied with blood (1 mark).
The placenta is a disc embedded in the uterine wall, with villi on the embryo's side and blood spaces on the mother's side surrounding the villi (1 mark).
This gives a large surface area for glucose and oxygen to pass from mother to embryo, and for the embryo's wastes to pass into the mother's blood (1 mark).

Answer: Via the placenta: villi and blood spaces give a large exchange surface for food, oxygen and wastes.

Example 4: Menstruation · 3 marks · Short answerHarder board level

Why does menstruation occur? How long does it usually last and how often does it occur?

Try it first, then show the solutionSolution

Each month an ovary releases one egg, and the uterus prepares to receive a fertilised egg: its lining becomes thick and spongy with a rich blood supply (1 mark).
If the egg is not fertilised (it lives about one day), this lining is not needed and slowly breaks down, leaving through the vagina as blood and mucus (1 mark).
This occurs roughly every month and usually lasts about two to eight days (1 mark).

Answer: Unneeded uterine lining is shed when the egg is not fertilised; roughly monthly, lasting about 2 to 8 days.

Example 5: From egg to foetus · 5 marks · Long answerHOTS / competency

Trace the events from the release of an egg to the formation of a foetus, naming the organ where each event happens. Explain why a blocked oviduct would prevent pregnancy.

Try it first, then show the solutionSolution

One ovary releases an egg; it enters the oviduct (fallopian tube) (1 mark).
Sperms travel up from the vagina through the uterus to the oviduct, where one may fuse with the egg: fertilisation, forming a zygote (1 mark).
The zygote divides to form a ball of cells, the embryo, which moves to the uterus and is implanted in its lining (1 mark).
The embryo is nourished through the placenta and develops organs, becoming a foetus over about nine months (1 mark).
If the oviduct is blocked, the egg cannot meet the sperms and cannot reach the uterus, so fertilisation and implantation cannot take place (1 mark).

Answer: Ovary → oviduct (fertilisation) → uterus (implantation, placenta) → foetus. A blocked oviduct stops egg and sperm meeting.

Where students lose marks in Human Reproductive System

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

Mistake: Wrong site of fertilisation
Students assume it happens in the uterus.
Wrong working
Fertilisation takes place in the uterus.
Right working
Fertilisation takes place in the oviduct (fallopian tube); the embryo implants in the uterus.
Do this: Oviduct = meeting place; uterus = growing place.
Usually costs: 1 mark.
Mistake: Vague placenta answer
Students write only 'the baby gets food from the mother'.
Wrong working
The baby gets food through the mother's blood.
Right working
Through the placenta: villi on the embryo's side and blood spaces on the mother's side give a large surface for glucose and oxygen to pass.
Do this: Name the placenta, villi and blood spaces.
Usually costs: 1-2 marks.
Mistake: Wrong reason for the scrotum
Students guess protection.
Wrong working
Testes are outside the body for protection.
Right working
Sperm formation needs a lower temperature than normal body temperature.
Do this: Learn the NCERT reason exactly.
Usually costs: 1 mark.
Mistake: Incorrect menstruation explanation
Students describe it without linking to fertilisation.
Wrong working
Menstruation removes impure blood from the body.
Right working
The uterine lining prepared for an embryo is shed when the egg is not fertilised.
Do this: Always link menstruation to the unfertilised egg and the unneeded lining.
Usually costs: 1-2 marks.

Exam tips

Practise labelled diagrams of the male and female reproductive systems from the NCERT figures.
Use correct terms: oviduct or fallopian tube, uterus, cervix, implantation, placenta.
When asked about functions, give each organ's role in one clear line.
For the placenta, mention both directions of exchange: food and oxygen in, wastes out.
Reproductive health and contraception are a separate topic; keep this answer to structure and function unless asked.

Practice questions on Human Reproductive System

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
Pick the odd one out, the organ that does not belong to the human female reproductive system:
(a) fallopian tube (b) vas deferens (c) uterus (d) ovary
Hint
One of these carries sperms.
Answer
(b) vas deferens, which carries sperms in males.
Q2 · 1 mark · Assertion-reasonHarder board level
Assertion (A): The testes are located outside the abdominal cavity.
Reason (R): Sperm formation requires a lower temperature than normal body temperature.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Where is the scrotum?
Answer
(a).
Q3 · 2 marks · Very short answerBoard level
Suppose two 13-year-old classmates compare notes: one has oily skin, pimples and new hair in the armpits, while the other has noticed no such changes yet and is worried. (a) Should the second student worry? Explain. (b) Name the hormone that brings on these changes in boys and in girls, with the gland that makes each.
Hint
Puberty changes come slowly and do not start at the same age in everyone.
Answer
(a) No. Puberty changes such as oily skin, pimples and thick hair in the armpits and genital area happen slowly, over months and years, and they begin at different ages in different people (1 mark). (b) Testosterone from the testes in boys; oestrogen from the ovaries in girls (1 mark).
Q4 · 4 marks · Case-basedHOTS / competency
Read the passage and answer.
Suppose a health teacher explains to a Class 10 group that a girl is born with thousands of immature eggs in her ovaries, but only after puberty does one egg mature and get released each month. The lining of the uterus also changes every month.
(a) Where are eggs made and where is an egg carried after release? (1 mark)
(b) What happens to the uterine lining each month in preparation for pregnancy? (1 mark)
(c) Explain what happens to the egg and the lining if fertilisation does not occur, and why this happens roughly monthly. (2 marks)
Hint
Link the monthly egg release to the monthly lining preparation.
Answer
(a) In the ovaries; it is carried through the oviduct (fallopian tube) towards the uterus. (b) It becomes thick and spongy with a rich blood supply to nourish an embryo. (c) The egg lives about one day and is lost; the lining, no longer needed, breaks down and leaves as blood and mucus (menstruation, about 2 to 8 days). Because an ovary releases one egg each month and the uterus prepares each time, the cycle repeats roughly monthly.
Q5 · 3 marks · Short answerHOTS / competency
Compare the placenta with the villi of the small intestine: what common design feature do they share and why?
Hint
Both are surfaces for taking in materials into blood.
Answer
Both have finger-like villi richly supplied with blood, giving a large surface area. In the small intestine, villi absorb digested food into the blood; in the placenta, villi on the embryo's side take up glucose and oxygen from the mother's blood spaces (and give out wastes). A large surface makes exchange efficient in both.
Q6 · 3 marks · Short answerHarder board level
List the parts of the male reproductive system in the order sperms pass through them, and give the function of each part you name.
Hint
Start where sperms are made.
Answer
Testes (in scrotum): produce sperms and testosterone. Vas deferens: carries sperms. Seminal vesicles and prostate (along the path): add fluid for easier transport and nutrition. Urethra: common passage for sperms and urine, leading out through the penis.

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.Where are sperms formed?Show answer
In the testes.
2.Which glands add fluid to sperms?Show answer
Prostate gland and seminal vesicles.
3.Where does fertilisation occur in humans?Show answer
In the oviduct (fallopian tube).
4.What is the placenta?Show answer
A disc embedded in the uterine wall through which the embryo gets nourishment from the mother's blood.
5.How long does an unfertilised egg live?Show answer
About one day.
6.How long does development inside the mother take?Show answer
About nine months.

Human Reproductive System: frequently asked questions

What are the parts of the male reproductive system?

Testes (in the scrotum), vas deferens, seminal vesicles, prostate gland, urethra and penis.

What are the parts of the female reproductive system?

Ovaries, oviducts (fallopian tubes), uterus, cervix and vagina.

What is the function of the placenta?

It lets glucose and oxygen pass from the mother's blood to the embryo and lets the embryo's wastes pass into the mother's blood, through a large surface of villi and blood spaces.

Why does menstruation happen?

Each month the uterine lining thickens to receive an embryo. If the egg is not fertilised, the lining is not needed and is shed as blood and mucus.

What is puberty?

The period in adolescence when reproductive tissues mature, shown by changes such as new hair growth, voice changes in boys and the start of menstruation in girls.