The Reproductive System

ICSE Class 10 · Biology · Chapter 13

What this chapter covers

Reproduction and the human reproductive system
Male reproductive organs and accessory glands
Female reproductive organs
Secondary sexual characters
Structure and functions of the sperm and the egg
Fertilisation, implantation, gestation and parturition
The placenta
Foetal membranes and amniotic fluid
The menstrual cycle
Role of sex hormones in reproduction
Identical and fraternal twins

Key definitions

Reproduction is the biological process by which living organisms produce new individuals of their own kind.

Sexual reproduction is the type of reproduction in which a male gamete and a female gamete fuse to form a zygote, which then develops into a new individual.

Gametes are the haploid reproductive cells, sperms in the male and eggs (ova) in the female, that fuse during fertilisation.

Gonads are the primary reproductive organs that produce gametes and sex hormones.

Testes are the pair of oval male gonads that produce sperms and the male sex hormone testosterone.

Scrotum is the pouch of skin that holds the testes outside the abdomen and keeps them at a temperature about 2 to 3 °C lower than normal body temperature.

Seminiferous tubules are the highly coiled tubules inside the testis in which sperms are produced.

Epididymis is the long, coiled tube lying along the back of each testis, in which sperms are stored for a while and become mature and able to swim.

Vas deferens is the thick muscular tube that carries sperms from the epididymis up into the abdominal cavity towards the urethra.

Urethra is the tube that runs through the penis and carries urine from the urinary bladder and semen from the ejaculatory ducts to the outside.

Penis is the male copulatory organ that carries the urethra and transfers sperms into the female's vagina.

Semen is the milky fluid made up of sperms suspended in the secretions of the seminal vesicles, prostate gland and Cowper's glands.

Key points

Humans reproduce sexually; haploid gametes (23 chromosomes each) fuse to form a diploid zygote (46 chromosomes).
Testes in the scrotum make sperms in seminiferous tubules and testosterone in interstitial cells; the scrotum keeps them 2–3 °C cooler.
Sperms pass through the epididymis, vas deferens, ejaculatory duct and urethra; seminal vesicles, prostate and Cowper's glands add fluids to form semen.
Ovaries make eggs and secrete oestrogen and progesterone; fallopian tubes carry the egg; the uterus houses the foetus; the vagina is the birth canal.
Secondary sexual characters appear at puberty under testosterone in boys and oestrogen in girls.
A sperm has a head with nucleus and acrosome, a neck, a middle piece with mitochondria, and a tail; the ovum is large, round and non-motile with a zona pellucida and corona radiata.
Fertilisation occurs in the fallopian tube; implantation in the endometrium about seven days later; gestation lasts about 280 days; parturition is driven by oxytocin.
The placenta handles the foetus's nutrition, respiration and excretion without the two bloods mixing, and secretes hCG, progesterone and oestrogen.
The amnion, chorion, allantois and yolk sac are the foetal membranes; amniotic fluid cushions and protects the foetus.
The 28-day menstrual cycle runs through menstruation, the follicular phase, ovulation on about day 14 and the luteal phase.
Testosterone, oestrogen and progesterone control sperm production, the female organs and cycle, and the maintenance of pregnancy.
Identical twins come from one zygote and share all genes; fraternal twins come from two eggs and two sperms.

Questions answered

Define gonads and name the gonads in the male and in the female.

Gonads are the primary reproductive organs that produce gametes and sex hormones. The male gonads are the testes and the female gonads are the ovaries.

Why are the testes located in the scrotum outside the abdominal cavity?

The scrotum keeps the testes about 2–3 °C below normal body temperature, and sperms are produced properly only at this lower temperature.

Name the part of the testis that produces (a) sperms and (b) testosterone.

(a) The seminiferous tubules. (b) The interstitial (Leydig) cells.

Give one function each of the seminal vesicles, the prostate gland and Cowper's glands.

Seminal vesicles add a fructose-rich fluid that gives sperms energy; the prostate adds an alkaline fluid that activates sperms; Cowper's glands lubricate and neutralise the urethra.

Name the part of the female reproductive system where (a) fertilisation and (b) implantation take place.

(a) The ampulla of the fallopian tube. (b) The endometrium of the uterus.

What is the function of the acrosome and of the middle piece of a sperm?

The acrosome contains enzymes that dissolve the coverings of the egg so the sperm can enter; the middle piece contains mitochondria that supply energy for the tail to swim.

Explain the terms gestation and parturition.

Gestation is the period of development of the embryo and foetus inside the uterus, about 280 days counted from the last menstrual period. Parturition is childbirth, in which the foetus is pushed out of the uterus by strong uterine contractions brought about by oxytocin.

State the role of the placenta in the nutrition, respiration and excretion of the foetus.

Digested food passes from the mother's blood to the foetus; oxygen passes to the foetus and carbon dioxide to the mother; urea passes from the foetus to the mother for removal by her kidneys.

Past board exam questions

ICSE 2027 sample paper · 5 marks

The ovaries are a pair of small oval-shaped reproductive organs situated in the pelvic cavity of a female. They perform two main functions – production of female gametes and secretion of hormones. These hormones regulate the menstrual cycle and bring about the development of secondary sexual characteristics in females. Select the correct terms to fill in the blanks: [fertilisation, 280, uterus, oviduct, ova, 40, ovulation, ovules, parturition] (a) The gametes produced by ovaries are called __________. (b) The release of a mature ovum from graafian follicle is known as __________. (c) Menstrual flow occurs when __________ of the female gamete fails to occur. (d) Implantation of the embryo is in the __________. (e) The gestation period lasts for __________ weeks.

Show answer

(a) ova (b) ovulation (c) fertilisation (d) uterus (e) 40

ICSE 2027 sample paper · 5 marks

Study the structures listed below and match the structure with its function: Example: Fallopian tube – (f) Structures (labelled around a human foetus inside the uterus): fallopian tube, placenta, uterus, umbilical cord, amniotic fluid, fetus, amnion, cervix Functions: (a) Allows diffusion of glucose from maternal blood into foetal blood (b) A tube-like structure that transports substances to and from the foetus (c) Protective membrane surrounding the foetus (d) Cushions the foetus and absorbs mechanical shocks (e) Dilates to enable the birth of baby (f) Site of fertilisation

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Placenta – (a) Umbilical cord – (b) Amnion – (c) Amniotic fluid – (d) Cervix – (e) (Fallopian tube – (f), given as the example.)

ICSE 2027 sample paper · 2 marks

State one difference between identical twins and fraternal twins.

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Identical twins develop from a single fertilised egg that divides into two, so they are always of the same sex (2 boys or 2 girls); fraternal twins develop from two separate eggs fertilised by two sperms, so they may be of the same or different sex (2 boys, 2 girls, or 1 boy and 1 girl).

ICSE 2026 sample paper · 1 mark

The hormone that maintains the thickening of the endometrium during pregnancy is:

Oestrogen
ACTH
Progesterone
Oxytocin

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Progesterone

ICSE 2026 sample paper · 1 mark

Tanvi tried to match the phases of menstrual cycle with the number of days as given in the table below: | PHASE | DAYS | |---|---| | P – Follicular Phase | Day 5 – 12 | | Q – Luteal Phase | Day 15 – 28 | | R – Menstrual Phase | Day 3 – 5 | | S – Ovulatory Phase | Day 13 or 14 | Identify the correct sequence:

P, Q, R, S
Q, S, R, P
R, P, S, Q
S, R, P, Q

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R, P, S, Q

ICSE 2026 board paper · 1 mark

During which phase of menstrual cycle does the endometrium shed?

Follicular phase
Ovulatory phase
Menstrual phase
Luteal phase

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Menstrual phase

ICSE 2026 board paper · 5 marks

Given below is the diagram of a human sperm. Read the information below the diagram and fill in the blanks: Living organisms reproduce to form new individuals of their own kind. This is essential for the survival and continuation of species. Human sperms are microscopic structures that carry genetic material. The head of the sperm has a cap like organelle called (a) __________ (Lysosome / Acrosome) which produces an enzyme (b) __________ (Hyaluronidase / Amylase) that dissolves the outer layer of the ovum to facilitate fertilisation. The nucleus of the sperm has (c) __________ (23 / 46) chromosomes. The middle piece has (d) __________ (Chloroplast / Mitochondria) to provide energy for the motility of the sperm. (e) __________ (Semen / Hymen) is a mixture of sperms and the fluids produced by the male accessory glands.

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(a) Acrosome (b) Hyaluronidase (c) 23 (d) Mitochondria (e) Semen

ICSE 2026 sample paper · 5 marks

Study the structures of the human testis listed below and match each structure with its function: Example: Scrotum - (f) Structures (labelled in a section of the human testis): Efferent Ducts, Seminiferous tubules, Interstitial cells, Vas deferens, Epididymis, Scrotum Functions: (a) Secrete Testosterone (b) Transports sperms to Epididymis (c) Stores sperms till maturation (d) Transport sperms to urethra (e) Produce sperms (f) Regulates temperature of Testis.

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Interstitial cells – (a) Efferent Ducts – (b) Epididymis – (c) Vas deferens – (d) Seminiferous tubules – (e) (Scrotum – (f), given as the example.)