Unit 1: Reproduction

Chapter 1.2: Human Reproduction

Male Reproductive System

• Primary Sex Organ: Testes
• Accessory Ducts: Rete Testis, Vasa Efferentia, Epididymis, Vas Deferens, Ejaculatory Duct, Urethra
• Accessory Glands: Seminal Vesicles, Prostate Gland, Bulbourethral Glands
• External Genitalia: Scrotum, Penis

Female Reproductive System

• Primary Sex Organs: Ovaries
• Accessory Ducts: Oviducts (Fallopian Tubes), Uterus, Vagina
• External Genitalia (Vulva): Mons Pubis, Labia Majora, Labia Minora, Hymen, Clitoris

Testis and Ovary Structure

• Testis:
  • Contains seminiferous tubules for sperm production.
  • Sertoli cells provide nourishment.
  • Leydig cells produce testosterone.
• Ovary:
  • Contains ovarian follicles at various stages.
  • Graafian follicle is the mature follicle.
  • Corpus luteum forms after ovulation.

Gametogenesis: Spermatogenesis

• Formation of sperm in the testes.
• Phases:
  1. Multiplication Phase: Spermatogonia (2n) divide by mitosis.
  2. Growth Phase: Primary spermatocytes (2n) are formed.
  3. Maturation Phase: Meiosis I and II produce four haploid spermatids (n).
• Spermiogenesis: Transformation of spermatids into spermatozoa (sperm).

Gametogenesis: Oogenesis

• Formation of ovum in the ovaries.
• Initiated during fetal development.
• Phases:
  • Multiplication & Growth: Primary oocytes (2n) arrested in Meiosis I.
  • Maturation: At puberty, Meiosis I completes, forming a secondary oocyte (n) and a polar body. Meiosis II completes only after fertilization.
• Produces one functional ovum and polar bodies.

Hormonal Control: Male

• Hypothalamus: GnRH
• Anterior Pituitary:
  • LH: Stimulates Leydig cells to produce testosterone.
  • FSH: Stimulates Sertoli cells.
• Testosterone: Stimulates spermatogenesis and secondary sexual characteristics.

Hormonal Control: Female

• Hypothalamus: GnRH
• Anterior Pituitary: FSH and LH
• FSH: Stimulates follicular growth and estrogen secretion.
• LH: Triggers ovulation and stimulates the corpus luteum.
• Estrogen & Progesterone: Regulate the menstrual cycle and support pregnancy.

Menstrual Cycle

• Cyclical changes in the uterus and ovaries (approx. 28 days).
• Phases:
  1. Menstrual Phase (Day 1-5): Endometrial breakdown.
  2. Follicular Phase (Day 5-14): Follicle growth, endometrium regenerates.
  3. Ovulatory Phase (Day 14): LH surge, ovulation.
  4. Luteal Phase (Day 15-28): Corpus luteum forms, secretes progesterone.

Fertilization

• Fusion of sperm and ovum in the fallopian tube.
• Events:
  • Capacitation: Sperm activation.
  • Acrosomal Reaction: Enzymes penetrate the egg.
  • Cortical Reaction: Blocks polyspermy.
  • Fusion of Pronuclei: Forms a diploid zygote.

Early Embryo Development

• Cleavage: Mitotic divisions of the zygote.
• Morula: 8-16 cell stage.
• Blastocyst: Forms by the time the embryo reaches the uterus.
  • Trophoblast: Outer layer (forms placenta).
  • Inner Cell Mass (ICM): Forms the embryo.

Implantation and Placenta

• Implantation: Blastocyst embeds in the endometrium (around day 7).
• Placenta:
  • Connection between fetus and mother.
  • Functions: Nutrient supply, waste removal, endocrine gland (hCG, hPL, estrogen, progesterone).

Parturition and Lactation

• Parturition (Childbirth):
  • Initiated by fetal ejection reflex.
  • Oxytocin causes uterine contractions.
• Lactation (Milk Production):
  • Prolactin stimulates milk production.
  • Oxytocin stimulates milk ejection.
  • Colostrum: First milk, rich in antibodies.