Note 65 - Reproductive Hormones - Reading

Human Reproductive System Overview

  • The human reproductive system consists of separate male and female systems.

  • Male gonads (testes) create sperm, while female gonads (ovaries) produce eggs.

  • Fertilization occurs when a male and female sex cell unite, forming a zygote that develops into an embryo and eventually a fetus.

Male Reproductive System

  • Castration increases body mass and affects aggression and sex drive in animals.

  • Male hormones: Testosterone and androsterone, mostly produced in interstitial cells of the testes.

Functions of Testosterone

  • Stimulates spermatogenesis (maturation of sperm cells).

  • Influences development of male secondary sexual characteristics (facial/body hair, voice deepening).

  • Involved in body oil production and linked to acne.

Hormonal Regulation

  • Hypothalamus and pituitary gland govern sperm and hormone production.

  • FSH (Follicle-Stimulating Hormone) promotes sperm production; LH (Luteinizing Hormone) stimulates testosterone production.

  • GnRH (Gonadotropin-Releasing Hormone) from the hypothalamus initiates the secretion of FSH and LH, which operates on a negative feedback loop to regulate hormone levels.

Female Reproductive System

  • More complex than the male system with a cyclic pattern of hormone fluctuations.

  • Daily egg maturation culminates in ovulation and requires multiple hormonal interactions.

Oogenesis and Ovulation

  • Ovaries contain follicles, which are cellular structures housing oocytes.

  • Each follicle develops primarily one ovum, degenerating others.

  • Females experience up to 400 maturing eggs from puberty to menopause.

Processes of Oogenesis

  • The primary oocyte undergoes meiosis, resulting in a secondary oocyte and polar body.

  • Ovulation occurs when the mature follicle releases the secondary oocyte.

Menstrual Cycle Phases

  1. Flow Phase - shedding of the endometrium (menstruation).

  2. Follicular Phase - follicles in ovaries mature and secrete estrogen.

  3. Ovulatory Phase - ovulation occurs; the egg is released.

  4. Luteal Phase - corpus luteum forms, secreting estrogen and progesterone to prepare the uterus for a possible pregnancy.

Hormonal Control

  • The hypothalamus and pituitary regulate estrogen and progesterone production through FSH and LH contributions.

  • A feedback loop is established where increased hormone levels inhibit further FSH and LH release.

Menopause and Its Effects

  • Menopause marks the end of the female reproductive period, accompanied by a significant drop in hormone levels, especially estrogen.

Birth Control Mechanism

  • Oral contraceptives usually contain progesterone that inhibits ovulation, thus preventing conception.