The Reproductive System of Humans

The male reproductive system

The testes produce sperm cells and the hormone testosterone. Sperm mature and are stored in the epididymis, then travel along the vas deferens during ejaculation.

The seminal vesicle and prostate gland add fluid to the sperm to form semen, which provides nutrients and a suitable medium for the sperm. Semen leaves the body through the urethra inside the penis, which deposits sperm into the female reproductive tract during copulation.

The female reproductive system

Each ovary releases one egg cell roughly every 28 days, a process called ovulation. The oviduct (fallopian tube) is where fertilisation normally takes place, and tiny hair-like cilia lining it sweep the egg towards the uterus.

The uterus has a thick, muscular wall and a lining, the endometrium, that thickens each cycle to receive a fertilised egg. The cervix is the narrow opening at the base of the uterus, and the vagina is the muscular canal that receives the penis during copulation and forms the birth canal.

Structure matched to function

• Testis, many coiled seminiferous tubules provide a large surface area for producing millions of sperm.
• Epididymis, a long, coiled tube that stores and matures sperm before ejaculation.
• Oviduct, cilia and muscular contractions move the egg towards the uterus; fertilisation happens here.
• Uterus, a thick muscular wall that can stretch enormously to hold a growing fetus.
• Placenta (formed after implantation), exchanges nutrients, gases and waste between mother and fetus.

How it is examined

SPM questions usually give a labelled diagram of the male or female system and ask you to name a structure and state its function, or to trace the pathway of sperm or an egg from where it is produced to where fertilisation or fertilisation-and-birth occurs.

Hormonal control of the reproductive systems

Both systems are controlled by hormones rather than by structure alone. In males, testosterone, produced by the testes, maintains sperm production and the male secondary sexual characteristics that develop at puberty, such as facial hair and a deeper voice.

In females, oestrogen and progesterone, produced mainly by the ovaries, regulate the menstrual cycle: oestrogen causes the uterine lining (endometrium) to thicken after menstruation and triggers ovulation, while progesterone maintains the thickened lining so that it is ready to receive a fertilised egg. If fertilisation does not occur, the levels of both hormones fall, the lining breaks down, and menstruation begins the next cycle.

Worked exam-style question

Question. Diagram Y shows the female reproductive system, with structures labelled P (ovary), Q (oviduct) and R (uterus). (a) State the process that occurs at P approximately every 28 days.

(b) Name the structure labelled Q, and state what normally happens there. (c) Explain how the wall of structure R is adapted to its function during pregnancy.

(d) After a sperm cell fertilises an egg cell at Q, describe what happens to the resulting cell before it reaches R.

Model answer. (a) Ovulation, the release of a mature egg cell (ovum) from the ovary. (b) Q is the oviduct (fallopian tube); fertilisation normally takes place here, where a sperm cell fuses with an egg cell to form a zygote.

(c) The wall of R (the uterus) is thick and muscular, allowing it to stretch considerably as the fetus grows, and it later contracts strongly to push the baby out during birth; its lining, the endometrium, is rich in blood vessels to nourish an implanted embryo. (d) The fertilised egg (zygote) undergoes repeated mitosis to form a ball of cells while being moved along the oviduct by ciliary action and muscular contractions towards the uterus, where it implants into the thickened endometrium.

Practice question

Try this. After a vasectomy (an operation that cuts and seals the vas deferens on both sides), a man can still ejaculate semen, but the semen no longer contains sperm. Explain why.

Exam tip

Key terms

These Chapter 15 terms describe the key events and structures of human reproduction:

• Fertilisation, the fusion of a sperm cell and an egg cell, normally occurring in the oviduct.
• Zygote, the single cell formed immediately after fertilisation, before it divides.
• Placenta, the organ that forms after implantation to exchange nutrients, gases and waste between mother and fetus.
• Menstrual cycle, the roughly 28-day hormonal cycle that prepares the uterus lining to receive a fertilised egg.

Source:SRC-DSKP-EN

Frequently asked questions

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