How do humans produce gametes, and how is the menstrual cycle controlled?
Sexual reproduction in humans: gametogenesis (spermatogenesis and oogenesis); the structure of the gametes; fertilisation; and the hormonal control of the menstrual cycle.
A focused answer to the Eduqas Component 2 statement on human reproduction. Covers spermatogenesis and oogenesis, the structure of the sperm and egg, fertilisation and the acrosome reaction, and the hormonal control of the menstrual cycle.
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What this dot point is asking
Eduqas wants you to describe spermatogenesis and oogenesis, describe the structure of the gametes and how they suit their functions, explain fertilisation, and explain the hormonal control of the menstrual cycle. This is the human-reproduction part of Component 2.
Gametogenesis
Gametes form by meiosis, halving the chromosome number to haploid so fertilisation restores the diploid number.
- Spermatogenesis (in the seminiferous tubules of the testes) produces four small, motile sperm per meiosis, continuously from puberty.
- Oogenesis (in the ovaries) produces effectively one large egg per meiosis (the unequal cytoplasm divisions form polar bodies), with most development paused until ovulation.
The structure of the gametes
Fertilisation
At fertilisation, a sperm reaches the egg and the acrosome reaction releases enzymes that digest a path through the egg's layers. The sperm and egg membranes fuse, the sperm nucleus enters, and the cortical reaction changes the egg membrane to prevent more sperm entering (ensuring only one fertilises, preventing polyspermy). The two haploid nuclei fuse to form a diploid zygote.
Hormonal control of the menstrual cycle
The cycle is controlled by hormones from the pituitary gland (FSH and LH) and the ovary (oestrogen and progesterone):
- FSH stimulates a follicle to develop and to secrete oestrogen.
- Oestrogen repairs and thickens the uterus lining, and as it rises it inhibits FSH and triggers a surge of LH (positive feedback).
- The LH surge triggers ovulation (release of the egg) and turns the empty follicle into the corpus luteum.
- The corpus luteum secretes progesterone, which maintains the lining and inhibits FSH and LH. If no pregnancy occurs, the corpus luteum breaks down, progesterone falls, and the lining is shed (menstruation), allowing FSH to rise again.
Examples in context
Example 1. The contraceptive pill. The combined pill contains oestrogen and progesterone, which inhibit FSH and LH, so no follicle matures and ovulation does not occur, a direct application of the negative feedback in the cycle.
Example 2. Fertility treatment with FSH. Women undergoing IVF are given FSH to stimulate several follicles to mature at once, so multiple eggs can be collected, applying the role of FSH in follicle development.
Try this
Q1. State two structural adaptations of a sperm cell and their functions. [2 marks]
- Cue. Any two: acrosome with enzymes (to digest the egg's layers); midpiece with mitochondria (ATP for movement); flagellum (propulsion); haploid nucleus (carries DNA).
Q2. Name the hormone that triggers ovulation. [1 mark]
- Cue. LH (luteinising hormone).
Q3. Explain the role of progesterone in the menstrual cycle. [2 marks]
- Cue. Secreted by the corpus luteum; maintains the thickened uterus lining and inhibits FSH and LH.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20195 marksExplain how the structure of a sperm cell is adapted to its functions.Show worked answer →
The acrosome at the head contains hydrolytic (digestive) enzymes that break down the layers around the egg, allowing the sperm to penetrate it.
The haploid nucleus carries the father's genetic material to combine with the egg's nucleus at fertilisation.
The midpiece is packed with mitochondria, which release ATP by aerobic respiration to power movement of the tail.
The flagellum (tail) beats to propel the sperm through the female tract towards the egg.
Markers reward the acrosome and its enzymes, the haploid nucleus, mitochondria in the midpiece providing ATP, and the tail for movement.
Eduqas 20215 marksExplain the roles of FSH, oestrogen, LH and progesterone in controlling the menstrual cycle.Show worked answer →
FSH (from the pituitary gland) stimulates a follicle in the ovary to develop and to secrete oestrogen.
Oestrogen stimulates the repair and thickening of the uterus lining and, as it rises, inhibits FSH and triggers a surge of LH (positive feedback near mid-cycle).
The LH surge stimulates ovulation (release of the egg) and the conversion of the empty follicle into the corpus luteum.
The corpus luteum secretes progesterone, which maintains the thickened uterus lining and inhibits FSH and LH; if no pregnancy occurs, the corpus luteum breaks down, progesterone falls and the lining is shed (menstruation).
Markers reward FSH stimulating follicle development and oestrogen secretion, oestrogen thickening the lining and triggering the LH surge, LH causing ovulation, and progesterone maintaining the lining.
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Sources & how we know this
- Eduqas A Level Biology Specification (A400) — Eduqas (2015)