Chapter 28 Study Notes

Chapter 28 Overview

  • Slide 55: Discusses today's lab related to the dissection of pig reproductive organs.
  • Lab Details:
      - Location: Room 208
      - Time: 10:00 AM
      - Activities include: Lecture, watching videos on dissections of pig testicles and ovaries, followed by actual dissection in the lab.

Meiosis and Oogenesis

  • Oogenesis: The growth and formation of the egg.
  • Ovarian Cycle: Comprised of two cycles:
      - Menstrual Cycle
      - Ovarian Cycle (the focus of the lecture)
  • Childhood Phase:
      - Inactive ovaries
      - Presence of primordial eggs at birth (approximately 1.5 to 2 million).
      - Primordial eggs die off through atresia, leading to about 400,000 by puberty, with only 500 used during a female's reproductive lifetime.

Folliculogenesis

  • Folliculogenesis: The formation and maturation of follicles surrounding the eggs, beginning at puberty.
  • Key Hormones:
      - Gonadotropin-releasing hormone
      - Follicle-stimulating hormone (FSH)
      - Luteinizing hormone (LH)

Phases of the Ovarian Cycle

  • 1. Follicular Phase: (Days 1-13)
      - 15 to 20 primordial follicles mature into primary follicles.
      - The specific reason for stimulation of certain follicles is unknown.
      - Fastest-growing follicle releases inhibin, inhibiting FSH production to suppress growth of other follicles.
  • 2. Ovulation:
      - Occurs on Day 14 of a 28-day cycle, characterized by the release of the secondary oocyte from the follicle.
      - Factors affecting cycle variations include environmental pollutants and health.

  - Understanding ovulation timing: Ovulation occurs approximately 14 days before menstruation.

  • 3. Luteal Phase:
      - Follicular cells transform into the corpus luteum, an endocrine gland producing progesterone and estrogen.
      - Regulates endometrial preparation for possible implantation.
      - If fertilization does not occur, the corpus luteum regresses into corpus albicans after 10-13 days, leading to menstruation.

Menstrual Cycle Phases

  • Menstrual Phase: (Days 1-5)
      - Shedding of the endometrial lining due to decreased hormone levels (progesterone and estrogen).
  • Proliferative Phase: (Days 6-14)
      - Building up of the endometrial lining due to increased estrogen levels.
  • Secretory Phase: (Days 15-28)
      - Continued hormone production from the corpus luteum, further preparing the endometrium for a potential embryo.

Menopause and Reproductive Health

  • Menopause: Characterized by the absence of menstruation for one year.
      - Normal onset is between ages 45 to 55.
      - Increased pollutants and hormonal influences can cause irregular cycles and variations in onset age.

Symptoms and Implications of Menopause

  • Loss of estrogen leads to:
      - Skin changes (dryness, wrinkles)
      - Vaginal atrophy causing dyspareunia (pain during intercourse)
      - Increased risk of osteoporosis due to calcium loss

Ovarian Cancer

  • Common primary malignancy affecting women.
  • Symptoms: Nonspecific at first (e.g., constipation, nausea, abdominal swelling).
  • Detection often requires biopsy.
  • Treatment varies based on cancer stage (surgery or chemotherapy).

Anatomy of the Female Reproductive System

  • Ovaries:
      - Female gonads producing eggs and hormones.
  • Uterine/Fallopian Tubes: Conduct eggs from ovaries to the uterus.
      - Infundibulum: Funnel-shaped section with fimbriae that guide the egg.
  • Uterus: Organ where implantation occurs.
      - Composed of three layers:
        - Perimetrium (outer layer)
        - Myometrium (smooth muscle layer)
        - Endometrium (inner layer, thickening during menstrual cycle)
  • Cervix: Debated as either part of the uterus or entry from the vagina, it helps seal the uterus and allows passage of menstrual fluid and childbirth.

Ectopic Pregnancy

  • Occurs when a fertilized egg implants outside the uterus, commonly in the fallopian tube due to obstruction or scarring, leading to serious health risks without timely surgical intervention.

External Genitalia

  • Mons Pubis: Fatty tissue over the pubic symphysis.
  • Labia Majora and Minora: Skin folds protecting the vaginal opening.
  • Clitoris: Erectile tissue homologous to the male penis, enriched with sensitive nerve endings.
  • Mammary Glands: Accessory glands producing breast milk.
      - Contain lactiferous ducts leading to the nipple, and produce colostrum (first milk rich in antibodies).

Lactation and Nursing

  • Hormones involved:
      - Prolactin (milk production)
      - Oxytocin (milk ejection during nursing)
      - Colostrum: First milk high in immunological benefits for newborns.

Contraception Methods

  • Abstinence: Only guaranteed method to prevent pregnancy.
  • Other methods:
      - Rhythm Method
      - Barrier Methods (e.g., condoms, IUDs)
      - Hormonal Contraceptives

Conclusion

  • Review and analyze the visual aids discussed during the lecture for clarity on all concepts. Prepare for practical dissection in lab today.