SCI10 Q3 MODULE2

Menstrual Cycle Overview

  • Menstruation signifies a girl's capability for reproduction.

  • The menstrual cycle is a series of hormonal changes that prepare the egg for potential fertilization and the uterus for pregnancy.

  • Regulated by a biological feedback system influenced by the hypothalamus, pituitary gland, and gonads (ovaries and testes).

  • Average menstrual cycle length: 28 days (can vary among individuals).

  • The cycle can be divided into two main phases: Follicular Phase and Luteal Phase.

Phases of the Menstrual Cycle

Follicular Phase (Days 1-14)

  • Begins on the first day of menstruation.

  • The anterior pituitary releases Follicle Stimulating Hormone (FSH).

  • FSH stimulates the growth and maturation of ovarian follicles, which produce estrogen.

  • Estrogen promotes the thickening of the endometrium (uterine lining).

  • Peak estrogen levels trigger the release of Luteinizing Hormone (LH), leading to ovulation.

  • Ovulation occurs around day 14, where the mature egg is released and can be fertilized by sperm.

Luteal Phase (Days 14-28)

  • Lasts from the day after ovulation until the day before the next period.

  • LH and FSH levels decrease after ovulation.

  • The empty follicle transforms into the corpus luteum, producing progesterone.

  • If fertilization does not occur, the corpus luteum degrades, leading to a drop in progesterone and estrogen levels.

  • Symptoms of Pre-Menstrual Syndrome (PMS) may occur during this phase: pimples, headaches, fatigue, mood swings, bloating, and breast swelling.

Hormonal Regulation in the Menstrual Cycle

  • Key Hormones and Functions:

    • FSH (Follicle Stimulating Hormone)

      • Stimulates follicle growth and estrogen secretion.

    • LH (Luteinizing Hormone)

      • Surge induces ovulation and the formation of corpus luteum.

    • Estrogen

      • Thickens endometrium; signals the release of LH.

      • Prevents multiple eggs from maturing.

    • Progesterone

      • Maintains thickened endometrium and inhibits further production of FSH and LH.

Feedback Mechanisms in the Menstrual Cycle

  • Negative Feedback: Inhibits hormone production when levels of a hormone are high (e.g., high estrogen inhibits FSH and LH).

  • Positive Feedback: Amplifies responses, such as uterine contractions during childbirth.

Additional Considerations

  • The menstrual cycle can continue for around 40 years, interrupted by pregnancy.

  • Normal menstrual discomfort may occur, but excessive pain should be evaluated by a medical professional.

Understanding Menstrual and Reproductive Health

  • The significance of understanding periods extends to family planning and preventing unwanted pregnancies.

  • Awareness of peak fertility days is crucial for contraceptive practices.

    • Most fertile days are roughly 5 days in the menstrual cycle per month.

  • Engage in open discussions about reproductive health to promote awareness and informed decision-making.