The Menstrual Cycle

Ms. Julie

Understanding the Female Reproductive System

Biology Presentation
Presented by Ms. Julie

What is the Menstrual Cycle?

The menstrual cycle is a natural, recurring process in the female reproductive system that prepares the body for potential pregnancy each month.

Duration

Lasts 28 days on average, though 21–35 days is considered normal and healthy.

Phases

Four main phases controlled by complex hormonal interactions.

Purpose

Prepares the uterus for potential pregnancy each month.

Did you know? The menstrual cycle is controlled by a delicate balance of hormones including estrogen, progesterone, FSH, and LH.
Phase 1

Menstruation

Days 1–5 — The beginning of a new cycle

Uterus Menstrual Flow
  • Uterine lining (endometrium) sheds, causing bleeding
  • Estrogen and progesterone levels are at their lowest
  • May cause cramps, fatigue, headaches, or mood changes
  • Average blood loss: 30-40 milliliters
Key: The first day of bleeding marks Day 1 of a new menstrual cycle.
Phase 2

Follicular Phase

Days 6–14 — Preparation for ovulation

FSH Uterus Ovary
  • FSH (Follicle Stimulating Hormone) rises from the pituitary gland
  • Follicles in the ovaries begin to develop and mature
  • Estrogen levels increase steadily
  • Uterine lining begins to thicken and rebuild
  • Energy levels typically increase during this phase

Follicles

Fluid-filled sacs in the ovaries that contain immature eggs. Each cycle, multiple follicles begin developing, but typically only one reaches maturity.

Energy

Rising estrogen often boosts mood and energy levels during this phase, making it a great time for physical activities and social engagement.

Phase 3

Ovulation

Day ~14 — The peak fertility window

LH Surge Egg Uterus
  • LH (Luteinizing Hormone) surge triggers egg release
  • Mature egg is released from the dominant follicle
  • Egg travels through the fallopian tube toward the uterus
  • Peak fertility window: 12-24 hours after ovulation
  • Sperm can survive up to 5 days, creating a wider fertility window
Key: This is the most fertile phase of the cycle. If sperm is present, fertilization can occur.
24 Hours egg survives
5 Days sperm survives
Phase 4

Luteal Phase

Days 15–28 — After ovulation preparation

Corpus Luteum Uterus Progesterone
  • The ruptured follicle transforms into the corpus luteum
  • Corpus luteum produces progesterone and some estrogen
  • Uterine lining continues to thicken and becomes more vascular
  • PMS symptoms may occur (bloating, mood changes, breast tenderness)
  • If no pregnancy occurs → corpus luteum breaks down → cycle restarts

Corpus Luteum

Temporary gland that produces progesterone to support potential pregnancy. If fertilization occurs, it continues producing hormones until the placenta takes over.

Hormone Drop

If no fertilization occurs, progesterone levels drop dramatically, causing the uterine lining to shed and menstruation to begin.

Key Hormones

The menstrual cycle is regulated by four primary hormones working in harmony.

Day 1 Day 7 Day 14 Day 21 Day 28 Estrogen Progesterone FSH LH

Estrogen

Builds uterine lining, regulates FSH/LH, boosts mood. Estrogen peaks just before ovulation and then declines.

Progesterone

Thickens lining, prepares for pregnancy, regulates cycle. Progesterone rises after ovulation to support potential pregnancy.

FSH

Stimulates follicle development in ovaries. FSH rises at the beginning of the cycle to recruit follicles for development.

LH

Triggers ovulation and corpus luteum formation. The LH surge is the hormonal signal that causes the mature egg to be released.

Cycle Summary

A complete overview of the menstrual cycle phases.

Phase Days Key Event Primary Hormone
● Menstruation 1–5 Uterine lining sheds Low
● Follicular 6–14 Follicles develop Estrogen ↑
● Ovulation ~14 Egg released LH surge
● Luteal 15–28 Lining thickens Progesterone ↑
Important: Every person's cycle is unique. Variations in length and symptoms are normal.

Thank You

The menstrual cycle is a vital biological process that reflects overall reproductive health.

Prepares for Pregnancy

Each cycle prepares the body for potential pregnancy by building and maintaining the uterine lining.

Health Indicator

Regular cycles often indicate good reproductive health and hormonal balance.

Natural Variation

Cycles vary naturally in length and symptoms per person. What is normal for one person may differ for another.

Remember: Always consult healthcare providers for personalized information and concerns about your menstrual health.

— Questions? —

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