Explain the hormonal control of ovulation during the human menstrual cycle.

IB DP Biology Higher Level (2023 syllabus) — D3.1 Reproduction · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Rising oestrogen from the developing follicle exerts a positive feedback effect on the hypothalamus and anterior pituitary, causing a surge in luteinising hormone (LH). The LH surge stimulates the mature Graafian follicle to rupture, releasing the secondary oocyte – ovulation. After ovulation, LH promotes the ruptured follicle to become the corpus luteum, which secretes progesterone (and oestrogen) to maintain and prepare the uterine lining for implantation.

Examiner tips

Use the sequence: oestrogen rise → positive feedback → LH surge → follicle rupture → corpus luteum formation and progesterone secretion.
Mention the role of the corpus luteum in preparing the endometrium for implantation.

Common mistakes

Confusing the roles of FSH and LH; FSH is involved in follicle growth, not the ovulation trigger.
Omitting the positive feedback mechanism or the corpus luteum’s hormone secretion.

Mark scheme (4 marks)

Rising oestrogen (from the developing follicle) triggers a positive feedback effect on the anterior pituitary / hypothalamus.
This positive feedback causes a surge in luteinising hormone (LH) released from the anterior pituitary.
The LH surge stimulates the mature (Graafian) follicle to rupture, releasing the secondary oocyte — this is ovulation.
After ovulation, LH stimulates the ruptured follicle to develop into the corpus luteum, which secretes progesterone (and oestrogen) to maintain the uterine lining / prepare the endometrium for implantation.

Key terms in this question

ovulation