Feedback Mechanisms in Female Reproductive System | Grade 10 Science DepEd MELC Quarter 3 Module 2

The video introduces the topic of feedback mechanisms in the female reproductive system, building upon previous discussions of male and female reproductive systems and their hormones. Hormones control the timing of egg release, coordinate ovum and uterine development, and regulate the monthly menstrual cycle, which typically starts between ages 10-13 and continues for about 40 years. Only one egg is usually produced during a 28-day cycle, controlled by Follicle Stimulating Hormone (FSH).

If an ovum is not fertilized, the corpus luteum degenerates, progesterone production stops, and the uterine membrane breaks down. This discharge of uterine tissues and the unfertilized egg is called menstruation. Female sex hormones control secondary sex characteristics, ovarian, and uterine cycles. During puberty, the pituitary gland directs the secretion of FSH and Luteinizing Hormone (LH), signaling the start of puberty, secondary sex characteristic development, and menarche (first menstruation).

At puberty, the pituitary gland initiates hormonal changes that enable pregnancy, known as the menstrual cycle, typically lasting 28 days. The cycle begins with the pituitary gland secreting increased FSH, stimulating follicle formation in the ovaries and estrogen secretion. As follicle cells develop and multiply, estrogen levels rise, prompting the pituitary gland to secrete LH, which stimulates ovulation. Ovulation, the release of a mature egg, usually occurs on day 14, and the egg is ready for fertilization for 24 hours.

Under LH influence, ruptured follicle cells develop into the corpus luteum, which produces more estrogen and progesterone. These hormones prepare the uterine wall for possible implantation of a fertilized egg. High levels of estrogen and progesterone exert negative feedback on the pituitary gland, inhibiting further LH and FSH secretion. This deprives the corpus luteum of hormones, causing its degeneration and affecting progesterone levels, leading to changes in the endometrial wall.

With low progesterone, the endometrium disintegrates, blood vessels rupture, and blood and endometrial tissues flow out as menstruation, lasting about 5 days (menstrual phase). After menstruation, estrogen from developing follicles rebuilds the endometrium (proliferative phase, days 6-14). Corpus luteum formation and progesterone secretion trigger the endometrium to double in thickness and mature its glands (secretory phase, day 15 until the next menstrual phase). Menstrual cramps result from strong uterine contractions due to excessive prostaglandin secretion caused by endometrial shedding and inflammation.

A feedback mechanism is a process where one substance's level influences another's. In the menstrual cycle, a negative feedback mechanism affects hormone production: high levels of one hormone inhibit another. FSH stimulates ovaries to release estrogen; high estrogen then prevents more FSH production. Estrogen stimulates LH release, which controls progesterone production. High progesterone then inhibits further LH release. During labor, a positive feedback mechanism occurs: the baby's head pressure on the cervix stimulates oxytocin release, which causes stronger contractions, leading to more oxytocin release until birth.

The menstrual cycle, a hormonal process preparing a woman's body for possible pregnancy, involves the follicle stage (ovarian follicle growth), ovulation stage (egg release), corpus luteum stage (uterine preparation for implantation), and menstrual flow stage (uterine lining breakdown). Key hormones and their functions: Estrogen (from follicle/ovary) develops female characteristics and thickens the endometrium. Progesterone (from corpus luteum/ovary) stimulates the endometrium and inhibits uterine contractions/ovulation. LH (from pituitary gland) develops/maintains the corpus luteum and stimulates ovulation. FSH (from pituitary gland) stimulates follicle formation in ovaries.