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Menstrual Cycle: Phases and Hormonal Control

The menstrual cycle is the cyclic change in ovary and uterus of a reproductive-age human female, involving menstruation, follicular development, ovulation and luteal phase under hormonal control.

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Student-friendly explanation

A typical menstrual cycle is about 28 days, though normal variation can occur. Menstruation marks shedding of the endometrial lining when pregnancy has not occurred. During the follicular phase, FSH supports follicular growth and estrogen helps rebuild the endometrium. A mid-cycle LH surge triggers ovulation, usually around day 14 in a 28-day cycle. After ovulation, the ruptured follicle forms the corpus luteum, which secretes progesterone and maintains the endometrium. If fertilisation and implantation do not occur, corpus luteum regresses, hormone levels fall and menstruation begins again. Exam questions often test phase-hormone-effect links.

How to write this in exams

  1. 1

    Start with the exact idea

    The menstrual cycle is the cyclic change in ovary and uterus of a reproductive-age human female, involving menstruation, follicular development, ovulation and luteal phase under hormonal control.

  2. 2

    Then show how to use it

    Day 1 begins with menstruation; FSH promotes follicular growth; estrogen rebuilds endometrium; LH surge causes ovulation near mid-cycle; corpus luteum forms; progesterone maintains endometrium; if no implantation occurs, corpus luteum regresses and bleeding starts again.

  3. 3

    Add one concrete example

    If a graph shows a sharp LH peak around mid-cycle, students should identify it as the event that triggers ovulation, not menstruation.

  4. 4

    Avoid this incomplete answer

    A common wrong answer is putting ovulation during menstruation. Ovulation is a mid-cycle event in a typical cycle, while menstruation begins the cycle.

Definition

The menstrual cycle is the cyclic change in ovary and uterus of a reproductive-age human female, involving menstruation, follicular development, ovulation and luteal phase under hormonal control.

Example

If a graph shows a sharp LH peak around mid-cycle, students should identify it as the event that triggers ovulation, not menstruation.

Rule to remember

Cycle rule: menstrual phase → follicular phase → ovulatory phase → luteal phase; falling ovarian hormones cause menstruation, while LH surge triggers ovulation.

Sequence to remember

Cycle rule: menstrual phase>
follicular phase>
ovulatory phase>
luteal phase; falling ovarian hormones cause menstruation, while LH surge triggers ovulation. Useful diagram labels are days 1-5 menstruation, follicular growth, LH surge, ovulation, corpus luteum, progesterone rise and endometrial thickness. Notice that ovarian and uterine events are parallel. Day 1 begins with menstruation; FSH promotes follicular growth; estrogen rebuilds endometrium; LH surge causes ovulation near mid-cycle; corpus luteum forms; progesterone maintains endometrium; if no implantation occurs, corpus luteum regresses and bleeding starts again

Memory hook

FSH grows follicle, estrogen rebuilds lining, LH releases oocyte, progesterone preserves lining.

Examples and method

Worked example

In an assertion-reason item, if assertion says LH surge causes ovulation and reason says corpus luteum secretes progesterone, both may be true but the reason does not directly explain the LH surge.

Method to apply

Day 1 begins with menstruation; FSH promotes follicular growth; estrogen rebuilds endometrium; LH surge causes ovulation near mid-cycle; corpus luteum forms; progesterone maintains endometrium; if no implantation occurs, corpus luteum regresses and bleeding starts again.

Diagram support

Useful diagram labels are days 1-5 menstruation, follicular growth, LH surge, ovulation, corpus luteum, progesterone rise and endometrial thickness. Notice that ovarian and uterine events are parallel.

How CBSE asks it

Asked through hormone graphs, phase identification, functions of FSH, LH, estrogen and progesterone, and cause of menstruation.

Avoid common mistakes

Common confusion

Students often say estrogen directly causes ovulation. In exam answers, the LH surge is the immediate trigger for ovulation.

Common wrong answer

A common wrong answer is putting ovulation during menstruation. Ovulation is a mid-cycle event in a typical cycle, while menstruation begins the cycle.

Exam tip

When writing phases, connect each phase with one ovarian event, one uterine change and the major hormone involved.

Quick check

What causes menstruation if pregnancy does not occur?

Menstruation occurs when the corpus luteum regresses, progesterone and estrogen levels fall, and the thickened endometrium breaks down and is shed.

Answer writing and exam use

1-mark answer

Define the cycle, list phases in order, mention ovarian event and uterine change in each phase, identify FSH, LH, estrogen and progesterone roles, and explain what happens if fertilisation does not occur.

2-mark answer

Define the cycle, list phases in order, mention ovarian event and uterine change in each phase, identify FSH, LH, estrogen and progesterone roles, and explain what happens if fertilisation does not occur.

3-mark answer

Define the cycle, list phases in order, mention ovarian event and uterine change in each phase, identify FSH, LH, estrogen and progesterone roles, and explain what happens if fertilisation does not occur.
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