Human Reproduction: Organs, Gametes and the Menstrual Cycle
Human reproduction, in the Cambridge IGCSE Biology syllabus (0610/0970), covers organs, gametes and the menstrual cycle: the basic structure of the male and female reproductive organs, the structural adaptations that distinguish a sperm cell from an egg cell, and a description of the menstrual cycle in terms of the physical changes to the uterus lining across its four named phases (menstrual, proliferative/follicular, ovulation, secretory/luteal), rather than the hormone-by-hormone mechanism covered separately elsewhere in the specification. It establishes the basic organ names, gamete comparison and cycle-stage sequence that the deeper mechanisms of fertilisation and hormonal control build on.
Before you start
No specific prerequisites - this is a good place to start.
Method
- Name the male reproductive organs in order along the reproductive tract and give a one-line function for each: testis (produces sperm and testosterone), scrotum (holds the testes at a suitable temperature), sperm duct (carries sperm towards the urethra), prostate gland (adds fluid to form semen), urethra and penis (deliver semen out of the body).
- Name the female reproductive organs in order and give a one-line function for each: ovary (produces egg cells and hormones), oviduct (carries the egg towards the uterus and is the usual site of fertilisation), uterus (where an embryo implants and develops), cervix (the neck of the uterus), vagina (receives the penis and is the birth canal).
- Compare the sperm cell and the egg cell directly, structure by structure: size (sperm is tiny with almost no cytoplasm; the egg is one of the largest human cells, full of cytoplasm), mobility (sperm has a tail/flagellum for swimming; the egg cannot move itself), number produced (millions of sperm per ejaculation; normally one egg per cycle), and each cell's role (the sperm delivers only a haploid nucleus; the egg provides the haploid nucleus plus the nutrients/cytoplasm to support early development).
- Give the menstrual cycle as four named phases in order, described by what is physically happening to the uterus lining and ovary, without needing the hormone names: the menstrual phase (the thickened uterus lining breaks down and is lost as bleeding, over the first few days of the cycle); the proliferative/follicular phase (the uterus lining regrows/thickens, while an egg matures in a follicle in the ovary); ovulation (the mature egg is released from the ovary, roughly midway through the cycle); the secretory/luteal phase (the thickened uterus lining is maintained, ready to receive a fertilised egg, until either implantation occurs or the lining breaks down again to restart the cycle).
- When a question asks only to 'describe' the cycle (a Cambridge-style command word), give the sequence of physical changes to the lining and ovary in the order above; save naming FSH, LH, oestrogen and progesterone for an 'explain' question that specifically asks for the hormonal control (Topic B5), since a 'describe' question is marked on the sequence of physical events, not the hormone mechanism.
- For a labelled diagram question, be ready to identify any of the organs above from a side-view (sagittal) diagram of the reproductive system, not only from a list, and to state its function from memory rather than only recognising its shape.
Worked example
Describe the sequence of changes to the uterus lining and the ovary during one menstrual cycle, from the start of menstruation to the point just before the next menstruation begins.
- Start at day 1: during the menstrual phase, the thickened uterus lining from the previous cycle breaks down and is lost as bleeding, over the first few days.
- Move to the next phase: during the proliferative phase, the uterus lining regrows and thickens, while, in the ovary, an egg matures inside a follicle.
- Describe the midpoint event: ovulation occurs roughly midway through the cycle, when the mature egg is released from the ovary.
- Describe the final phase: during the secretory phase, the thickened uterus lining is maintained (ready to receive a fertilised egg if fertilisation has occurred).
- Close the sequence: if fertilisation does not occur, the lining is not maintained further and breaks down again, restarting the cycle with the next menstrual phase.
- Final answer: the cycle follows the order menstrual phase (lining lost) then proliferative phase (lining regrows, egg matures) then ovulation (egg released) then secretory phase (lining maintained), before the sequence repeats.
Practice questions
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Q1Name the female organ in which an egg cell matures.Show answer
Answer: The ovary.
Q2Name the male organ that produces testosterone.Show answer
Answer: The testis.
Q3State one structural difference between a sperm cell and an egg cell.Show answer
Answer: Any one of: the sperm has a tail (flagellum) and the egg does not; the egg is much larger and contains far more cytoplasm than the sperm; the sperm is motile (can swim) and the egg cannot move itself.
Q4Name the phase of the menstrual cycle during which the uterus lining breaks down and is lost.Show answer
Answer: The menstrual phase.
Q5State what happens to the uterus lining during the secretory (luteal) phase of the cycle.Show answer
Answer: It is maintained (kept thickened), ready to receive a fertilised egg if implantation is going to occur.
Q6Describe, in order, the four named phases of the menstrual cycle.Show answer
Answer: Menstrual phase (lining breaks down and is lost), proliferative phase (lining regrows/thickens, egg matures), ovulation (mature egg released), secretory phase (lining maintained).
Exam-style questions
Written in the style of a IGCSE Science exam paper, with a full mark scheme.
State the name of the male organ that carries sperm towards the urethra, and the name of the female organ that is the usual site of fertilisation.
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A textbook diagram shows the uterus lining thickness measured across a 28-day cycle: 2 mm on day 1, rising to 10 mm by day 14, staying at approximately 10-11 mm from day 15 to day 26, then falling back to 2 mm by day 28. Identify which named phase of the cycle corresponds to days 1-5, and which corresponds to days 15-26, using the data given, and explain what is happening to the lining in each.
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Describe the basic structure of the human male and female reproductive systems, name the main organs involved, and describe how the sperm cell and egg cell differ in structure and in the number produced.
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Free printable worksheet
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This topic is chapter 10 of IGCSE Science Workbook, the whole course as one free printable PDF.
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