BiologyICSE Class 10 · Reproductive System

Ovary, Ovulation and the Menstrual Cycle: Follicle, Corpus Luteum and Hormones (ICSE Class 10)

Updated 16 October 2026 · Fact-checked

Each month a follicle in the ovary matures into a Graafian follicle, which bursts at about day 14 of a 28-day cycle to release an ovum (ovulation). The empty follicle becomes the corpus luteum, which secretes progesterone to keep the uterine lining ready. If the ovum is not fertilised, progesterone falls and the lining is shed: menstruation.

Understand Ovary, Ovulation and the Menstrual Cycle

The ovary. The two ovaries lie in the lower abdomen. They have two jobs: they produce ova (eggs) and they secrete the female sex hormones, oestrogen and progesterone. A girl is born with thousands of immature eggs, each inside a small primary follicle. From puberty, usually one follicle matures each month.

Events in the ovary.
1. Follicle grows: a primary follicle enlarges, filled with fluid, and its cells secrete oestrogen.
2. Graafian follicle: the fully mature follicle, containing a mature ovum, bulges from the surface of the ovary.
3. Ovulation: the Graafian follicle bursts and releases the ovum, at about day 14 of a 28-day cycle. (A surge of the pituitary hormone LH triggers it.) The ovum is caught by the fimbriae of the oviduct.
4. Corpus luteum: the empty, ruptured follicle turns into a yellowish body, the corpus luteum, which secretes progesterone (and some oestrogen).
5. If the ovum is not fertilised, the corpus luteum degenerates after about two weeks.

The menstrual cycle. The menstrual cycle is the series of changes in the ovary and the uterus that repeats about every 28 days, from the first menstruation at puberty (menarche) until it stops at around 50 years (menopause).

Phase	Days (28-day cycle)	Ovary	Uterus
Menstrual	1–5 (lasts 3–5 days)	corpus luteum of the last cycle has degenerated	lining breaks down and is shed with blood: menstruation
Follicular (proliferative)	6–13	follicle grows; oestrogen rises	lining is repaired and thickens
Ovulation	about 14	Graafian follicle releases the ovum	lining thick
Luteal (secretory)	15–28	corpus luteum secretes progesterone	lining becomes thick, spongy, glandular and rich in blood vessels, ready for implantation

Why menstruation happens. The lining is prepared every month to receive an embryo. If fertilisation does not occur, the corpus luteum degenerates, progesterone falls, and the lining can no longer be maintained, so it breaks down. If fertilisation does occur, the corpus luteum (and later the placenta) keeps progesterone high, so the lining is kept and the cycles stop during pregnancy.

Roles of the hormones.

Oestrogen (growing follicles): repair and growth of the uterine lining; development of female secondary sexual characters (breasts, broader hips).
Progesterone (corpus luteum): makes the lining thick and glandular and maintains it for implantation and pregnancy.

Cycles of different lengths. Cycle length varies from person to person. The time from ovulation to the next menstruation (the luteal phase) is fairly constant at about 14 days, so in a longer cycle ovulation comes later and the follicular phase is longer.

Missed periods. Lack of menstruation may indicate pregnancy, but it can also be caused by stress or poor health.

Ovary, Ovulation and the Menstrual Cycle: key facts

Events in the ovary: Primary follicle grows
Graafian follicle bursts (ovulation, about day 14)
Corpus luteum forms
Corpus luteum degenerates if no fertilisation; The ovum leaves at ovulation; the corpus luteum stays in the ovary.
Phases (28 days): Menstrual days 1–5
Follicular days 6–13
Ovulation about day 14
Luteal days 15–28; Luteal phase about 14 days in most cycles.
Hormones: Oestrogen from the growing follicle, rebuilds the lining
Progesterone from the corpus luteum, thickens and maintains the lining
Fall in progesterone menstruation; Progesterone stays high in pregnancy.

Menstrual	days 1–5
Follicular	days 6–13
Ovulation	about day 14
Luteal	days 15–28

Oestrogen	from the growing follicle, rebuilds the lining
Progesterone	from the corpus luteum, thickens and maintains the lining
Fall in progesterone	menstruation

How to answer Ovary, Ovulation and the Menstrual Cycle questions

Questions on this topic test the order of events and the link between each event and its hormone.

1Fix the order in the ovary: follicle grows, Graafian follicle, ovulation, corpus luteum, degeneration.
2Match each phase to the hormone in charge: follicular with oestrogen, luteal with progesterone.
3Use full terms: 'Graafian follicle', 'corpus luteum', 'ovulation'.
4For 'why' questions, follow the chain: no fertilisation → corpus luteum degenerates → progesterone falls → lining breaks down.
5For dates, count day 1 as the first day of menstruation; ovulation is about 14 days before the next period.

Ovary, Ovulation and the Menstrual Cycle in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Marking a calendar

Suppose your elder sister notes that her period began on 3 March and that her cycles are regularly 28 days long.

On about which date would she ovulate, and when would her next period be expected?

Try it first, then show the solutionSolution

Day 1 is 3 March, so day 14 is 16 March: ovulation.
The next cycle starts on day 29, which is 31 March.

Answer: Ovulation about 16 March; next period about 31 March.

Memory hook: Day 1 is the first day of bleeding.

A late period before exams

Imagine a student finds her period comes several days late during a stressful exam month, though she is otherwise healthy.

Explain how stress could delay the cycle.

Try it first, then show the solutionSolution

The cycle is controlled by hormones from the pituitary and the ovaries.
Stress can upset this hormone release, so the follicle matures and ovulation happens later.
Since the luteal phase lasts about 14 days after ovulation, menstruation also comes later.

Answer: Stress delays ovulation through hormone changes, so menstruation is delayed.

Memory hook: Late ovulation, late period.

Tricks to remember Ovary, Ovulation and the Menstrual Cycle

Short memory aids. Say each one aloud once, then use it on a question the same day.

Oestrogen builds, progesterone protects
Oestrogen rebuilds the lining in the first half; progesterone protects (maintains) it in the second half.
Use it when: Matching hormones to phases.
Fourteen from the end
Ovulation is about 14 days before the next period, whatever the cycle length.
Use it when: Date questions.
Luteum = yellow
Corpus luteum means 'yellow body': what the burst follicle becomes.
Use it when: Naming the structure after ovulation.

Ovary, Ovulation and the Menstrual Cycle: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Lining rebuilt · 1 mark · MCQBoard level

In which phase of the menstrual cycle is the uterine lining repaired and thickened under the influence of oestrogen?
(a) menstrual phase
(b) follicular (proliferative) phase
(c) luteal phase
(d) menopause

Try it first, then show the solutionSolution

Oestrogen from the growing follicle rebuilds the lining after menstruation: the follicular phase.

Answer: (b) follicular (proliferative) phase

Example 2: Order of ovarian events · 2 marks · Short answerBoard level

Arrange these events in the ovary in the correct order: (A) corpus luteum forms; (B) a primary follicle grows; (C) the corpus luteum degenerates; (D) the Graafian follicle ruptures. Which of these events would not take place in that cycle if the ovum were fertilised?

Try it first, then show the solutionSolution

B → D → A → C. (1)
C: after fertilisation the corpus luteum is kept and goes on secreting progesterone, so it does not degenerate. (1)

Answer: B, D, A, C; C would not happen.

Example 3: Reading a hormone graph · 3 marks · Short answerHarder board level

A graph of a 28-day cycle shows hormone P rising from day 6 to day 13, and hormone Q high from day 15 to about day 26, then falling. (a) Identify P and Q and the structure that secretes each. (b) What happens in the uterus when Q falls?

Try it first, then show the solutionSolution

(a) P: oestrogen, from the growing (Graafian) follicle. (1)
Q: progesterone, from the corpus luteum. (1)
(b) The lining is no longer maintained; it breaks down and menstruation begins. (1)

Answer: (a) P oestrogen (follicle); Q progesterone (corpus luteum) (b) Menstruation

Example 4: Graafian follicle or corpus luteum? · 2 marks · Short answerHarder board level

Give two differences between a Graafian follicle and a corpus luteum.

Try it first, then show the solutionSolution

Time: the Graafian follicle exists before ovulation; the corpus luteum forms after it from the ruptured follicle. (1)
Contents and hormone: the Graafian follicle contains the mature ovum and secretes oestrogen; the corpus luteum has no ovum and secretes progesterone. (1)

Answer: Before vs after ovulation; contains ovum and secretes oestrogen vs no ovum and secretes progesterone.

Example 5: A longer cycle · 2 marks · Short answerHarder board level

Suppose a woman has regular 32-day cycles and her luteal phase lasts 14 days, as usual. (a) On which day does she ovulate? (b) Taking menstruation as days 1–5, how long is her follicular phase compared with that in a 28-day cycle?

Try it first, then show the solutionSolution

(a) 32 − 14 = 18: ovulation on about day 18. (1)
(b) Days 6–17 = 12 days, against days 6–13 = 8 days in a 28-day cycle; the extra length is in the follicular phase. (1)

Answer: (a) Day 18 (b) 12 days instead of 8

Example 6: Case study: extra progesterone · 3 marks · Case-basedHOTS / competency

Suppose, in a hormone study, a woman whose ovum was not fertilised is given progesterone tablets every day from day 15 to day 35 of her cycle (in a normal 28-day cycle her period would start on day 29).
(a) Predict when her menstruation will start.
(b) Explain your prediction.
(c) Which natural structure normally keeps progesterone high in early pregnancy?

Try it first, then show the solutionSolution

(a) It will be delayed until after the tablets stop (after day 35). (1)
(b) Menstruation is triggered by the fall in progesterone; while progesterone is supplied, the lining is maintained even though the corpus luteum has degenerated. (1)
(c) The corpus luteum (later, the placenta). (1)

Answer: (a) After day 35 (b) Progesterone keeps the lining; its fall triggers shedding (c) Corpus luteum, then placenta

Where students lose marks in Ovary, Ovulation and the Menstrual Cycle

The slips examiners see most often, and what to write instead.

Mistake: Implantation for ovulation; Graafian follicle for corpus luteum
CISCE examiners' comments, 2024 Q6(iv): on a section of the ovary, candidates wrote implantation instead of ovulation and Graafian follicle instead of corpus luteum.
Wrong working
Release of the ovum: implantation. Structure left behind: Graafian follicle.
Right working
Release of the ovum: ovulation. Structure left behind: corpus luteum.
Do this: Ovulation happens in the ovary; implantation in the uterus.
Usually costs: 1 mark each.
Mistake: Incomplete name of the follicle
CISCE examiners' comments, 2025 Q2(i)(a): for the fully developed part of the ovary containing a mature ovum, candidates wrote 'ovum' or 'follicle' instead of Graafian follicle.
Wrong working
Follicle.
Right working
Graafian follicle.
Do this: A mature follicle is always a 'Graafian follicle'.
Usually costs: 1 mark.
Mistake: Hormones swapped between phases
Writing progesterone for the follicular phase or oestrogen for maintaining the lining reverses the whole explanation.
Wrong working
Progesterone repairs the lining after menstruation.
Right working
Oestrogen repairs it; progesterone maintains it.
Do this: First half oestrogen, second half progesterone.
Usually costs: 1 mark.

Exam tips

Use the exact terms: Graafian follicle, ovulation, corpus luteum, endometrium.
Explain menstruation as a chain: no fertilisation → corpus luteum degenerates → progesterone falls → lining shed.
Give the day of ovulation as 'about day 14 of a 28-day cycle'.
When a diagram of the ovary is given, decide first whether it shows before or after ovulation.

Practice questions on Ovary, Ovulation and the Menstrual Cycle

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
In a regular 28-day cycle, ovulation occurs on about:
(a) day 1
(b) day 5
(c) day 14
(d) day 28
Hint
Mid-cycle.
Answer
(c) day 14
Q2 · 2 marks · Very short answerBoard level
Define (a) menarche, (b) menopause.
Hint
Start and stop.
Answer
(a) The first menstruation, at puberty. (b) The permanent stopping of menstrual cycles, at around 50 years of age.
Q3 · 2 marks · Very short answerBoard level
Name two female secondary sexual characters brought about by oestrogen.
Hint
Changes at puberty.
Answer
Development of breasts; broadening of the hips (also onset of menstruation).
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): The corpus luteum degenerates if the ovum is not fertilised.
Reason (R): The level of progesterone falls after the corpus luteum degenerates.
(a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
(c) (A) is true and (R) is false.
(d) (A) is false and (R) is true.
Hint
Is the fall a cause or a result?
Answer
(b) Both are true, but the fall in progesterone is a result of the degeneration, not its cause.
Q5 · 2 marks · Short answerHarder board level
Why does the uterine lining become thick, spongy and richly supplied with blood in the second half of the cycle?
Hint
What might arrive in the uterus?
Answer
Progesterone from the corpus luteum prepares the lining to receive and nourish an embryo, in case the ovum is fertilised and implants.
Q6 · 2 marks · Short answerHarder board level
Where is the ovum released, and what catches it? Why is it important that it is caught quickly?
Hint
The ovum lives for about a day.
Answer
It is released from the surface of the ovary when the Graafian follicle bursts; the fimbriae of the oviduct catch it. An unfertilised ovum lives only about a day, so it must reach the oviduct quickly to meet sperms.
Q7 · 3 marks · Short answerHOTS / competency
Suppose a woman with regular 30-day cycles starts her period on 10 July, and her luteal phase lasts 14 days. On which day of the cycle and on what date does she probably ovulate? When will her next period begin?
Hint
Count back 14 days from the next day 1.
Answer
Ovulation on day 30 − 14 = 16, which is 25 July. Next period on day 31 of the count, which is 9 August.
Q8 · 2 marks · Short answerHOTS / competency
Predict two effects on the menstrual cycle if both ovaries of a young woman had to be removed by surgery. Explain.
Hint
What do ovaries make?
Answer
No ova would be released, so there would be no ovulation; no oestrogen or progesterone would be made, so the uterine lining would not be built up each month and menstrual cycles would stop.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.How long does menstrual flow usually last?Show answer
About 3–5 days.
2.How long does an unfertilised ovum live?Show answer
About one day.
3.Phase in which the corpus luteum is active?Show answer
The luteal (secretory) phase.
4.Hormone whose fall triggers menstruation?Show answer
Progesterone.
5.Average length of the menstrual cycle?Show answer
About 28 days.

Ovary, Ovulation and the Menstrual Cycle: frequently asked questions

What is ovulation?

Ovulation is the release of a mature ovum from the Graafian follicle of the ovary, at about day 14 of a 28-day cycle. The ovum is then caught by the fimbriae of the oviduct.

Which hormone triggers ovulation?

A sudden surge of luteinising hormone (LH) from the pituitary in the middle of the cycle makes the Graafian follicle burst. ICSE asks mainly for the roles of oestrogen and progesterone, so treat LH as background.

Does ovulation always happen on day 14?

Only in a 28-day cycle. Ovulation usually comes about 14 days before the next period, so in a 32-day cycle it is near day 18 and in a 25-day cycle near day 11.

How much of the menstrual cycle does ICSE need?

An outline: the phases, ovulation, the corpus luteum and the roles of oestrogen and progesterone. Detailed pituitary hormone graphs are not required.