The menstrual cycle
A cycle of about 28 days has menstrual, follicular, ovulatory and luteal phases. FSH, LH, estrogen and progesterone drive it and prepare the uterus for pregnancy.
Phases of a 28-day menstrual cycle (days marked typical vary from woman to woman)
| Phase | Days (typical) | Ovary | Uterus | Hormones |
|---|---|---|---|---|
| Menstrual | Starts on day 1; flow lasts 3 to 5 days (textbook) | Corpus luteum of the last cycle has degenerated | Endometrium and its blood vessels break down; the liquid flows out through the vagina | Progesterone has fallen |
| Follicular | Typically about 6 to 13 | Primary follicles grow into a mature Graafian follicle | Endometrium regenerates by proliferation | FSH and LH rise gradually; growing follicles secrete estrogens |
| Ovulatory | About day 14 (textbook) | Graafian follicle ruptures and releases the ovum (ovulation) | Endometrium is thick | LH and FSH peak; the LH surge causes ovulation |
| Luteal | Typically about 15 to 28 | Remains of the follicle form the corpus luteum | Endometrium is maintained, ready for implantation | Progesterone is high |
Draw it: the cycle in one loop
- back to Menstruation
If the ovum is fertilised, and if it is not
A missed period may be a sign of pregnancy, but it can also be caused by stress, poor health or other reasons.
How to draw and read the menstrual cycle graph
- Draw a horizontal axis marked days 1 to 28. Mark the menstrual, follicular, ovulatory and luteal phases along it, with ovulation at about day 14.
- Stack four panels on this axis: pituitary hormones (LH, FSH), ovarian events (growing follicle, Graafian follicle, ovulation, corpus luteum), ovarian hormones (estrogen, progesterone) and the uterine lining (endometrium). Label every curve. Title: Events of the menstrual cycle.
- FSH and LH rise slowly in the follicular phase and peak at about day 14. The tall, sharp LH peak is the LH surge.
- Estrogen rises as the follicle grows and peaks just before ovulation.
- Progesterone stays low until ovulation, rises in the luteal phase, and falls just before menstruation.
- The endometrium is shed in the menstrual phase, then thickens through the follicular and luteal phases.
- If progesterone stays high and no menstruation follows, think of pregnancy.
Menstrual hygiene
- Bathe and keep yourself clean regularly. Use sanitary napkins or clean homemade pads, for example of clean cotton cloth.
- Change them every 4 to 5 hours, or as needed.
- Dispose of used napkins wrapped in paper. Never throw them into drains, toilets or open areas.
- Wash hands with soap after handling them.
- Regular cycles between menarche and menopause are a sign of normal reproductive health.
Clean toilets, water and sanitary napkins in schools help girls attend class during their periods. Noting the start date of each period in a calendar or phone helps a girl spot changes early and talk to a doctor.
5 marks: “Describe the events of the menstrual cycle and the role of the pituitary and ovarian hormones in each phase.” Menstrual phase (breakdown of endometrium); follicular phase (FSH, LH rise; follicle grows and secretes estrogen; endometrium regenerates); ovulatory phase (LH surge on about day 14 ruptures Graafian follicle); luteal phase (corpus luteum secretes progesterone, maintains endometrium); no fertilisation → corpus luteum degenerates → menstruation.
2 marks: “What is the LH surge? What happens because of it?” The rapid rise of LH to its peak in the middle of the cycle (about day 14). It makes the Graafian follicle rupture and release the ovum (ovulation).
1 marks: “Name the hormone secreted by the corpus luteum.” Progesterone.
Phases in order: 'My Friend Often Laughs': Menstrual, Follicular, Ovulatory, Luteal.