Germinal Epithelium

• Outline of General Embryo Lectures

  • Lect1 – General to Implantation
  • Lect2 – Bilaminar & Trilaminar Germ Disc
  • Lect3 – Gastrulation & Neurulation
  • Lect4 – Germinal Epithelium
  • Lect5 – Placenta

  
• Testes


  • Organ made up of thousands of seminiferous tubules where the sperm is produced
  • Surrounded by a fibrous capsule and partially enclosed by a serous membrane
  • The fibrous capsule divides the testicles into lobules filled with seminiferous tubules
  • They are innervated by a visceral sensory nerves very sensitive to pain
• Seminiferous tubules


  • Consist of a thick stratified epithelium surrounding a lumen
  • The epithelium has spermatogenic cells that mature into sperm
  • At puberty the seminiferous tubules begin to produce about 400 million sperm
  • The spermatogenic cells are protect by a blood-testis barrier that keep the cells from activating the immune system
• Spermatogenesis: sperm formation


  1. Formation of Spermatocytes

  2. Meiosis

  3. Spermiogenesis
• Ovaries


  • Paired organ suspended by mesenteries and ligaments
  • Can be divided into a cortex and medulla
  • The cortex houses the developing ova and the medulla holds vascular tissue
  • The site of oogenesis and female sex hormone production
  • Responds to follicle-stimulating hormone that signals the maturation of an ovum
  • Typically only one egg is released from an ovary every month
  • Hormones that affect the menstrual cycle and female sex organs are also released by the ovaries; estrogen and progesterone
• Oogenesis


  1. During fetal development oocytes undergo meiosis I but do not complete it; at this point they are called primary oocytes

  2. At ovulation the primary oocyte completes meiosis I and begins meiosis II

  3. Meiosis II is completed only if fertilization occurs

  4. At the completion of meiosis II the oocyte is called an ovum

  5. Primary oocytes remain in prophase and do not finish their first meiotic division before puberty is reached
• Uterine cycle


  • Menstrual phase (days 1-5)
  • Proliferative phase (days 6-14)
  • Secretory phase (days 15-28)
• Twins


  • Dizygotic
  • Monozygotic