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Yasser Orief M.D. Lecturer of Obstetrics & Gynecology, Alexandria University

The Physiology of conception. Yasser Orief M.D. Lecturer of Obstetrics & Gynecology, Alexandria University Fellow, L ϋ beck University, Germany DGOL, Auvergné University, France. Hypothalamo – Pituitary – Gonadal axis. The Reproductive System. Gonads – primary sex organs

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Yasser Orief M.D. Lecturer of Obstetrics & Gynecology, Alexandria University

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  1. The Physiology of conception Yasser Orief M.D. Lecturer of Obstetrics & Gynecology, Alexandria University Fellow, Lϋbeck University, Germany DGOL, Auvergné University, France

  2. Hypothalamo – Pituitary – Gonadal axis

  3. The Reproductive System • Gonads – primary sex organs • Testes in males • Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones • Sperm – male gametes • Ova (eggs) – female gametes

  4. Testes

  5. Male Reproductive System

  6. Processes of Spermatogenesis

  7. Female Reproductive System

  8. Female Reproductive System

  9. Ovaries

  10. Oogenesis

  11. Folliculogenesis • It begins by the recruitment of a cohort of primordial follicles into a pool of growing follicles and ends by either ovulation or atresia. It requires almost one year for a primordial follicle to grow and develop to the ovulatory stage.

  12. Gougeon A: Dynamics of follicular growth in the human: A model from preliminary results. Hum Reprod 1:81, 1986. Reproduced with permission from Oxford University Press.)

  13. Folliculogenesis, starting from pre-antral (late secondary) stage.

  14. The Hormonal Regulation of Ovarian Activity

  15. The 2 cell 2 gonadotropin theory

  16. The Hormonal Regulation of the Female Reproductive Cycle

  17. Hormonal Control of the Ovarian and Uterine Cycles

  18. Physiology of Menstruation

  19. Menstrual (Uterine) Cycle • Cyclic changes of the endometrium • Regulated by cyclic production of estrogens and progesterone • Stages of the menstrual cycle • Menses – functional layer of the endometrium is sloughed • Proliferative stage – regeneration of functional layer • Secretory stage – endometrium increases in size and readies for implantation

  20. The Hormonal Regulation of the Female Reproductive Cycle

  21. Hormonal Control of the Ovarian and Uterine Cycles

  22. Stages of Pregnancy and Development • Fertilization • Embryonic development • Fetal development • Childbirth

  23. Fertilization • The oocyte is viable for 12 to 24 hours after ovulation • Sperm are viable for 12 to 48 hours after ejaculation • Sperm cells must make their way to the uterine tube for fertilization to be possible

  24. Fertilization • Divided into 4 steps: • 1. Contact and recognition (“Casual Introductions”) • Sperm undergo capacitation (further maturation) within the female reproductive tract • Recall that sperm were produced in the testes and matured in the epididymus until ejaculation • Sperm reach the egg in the oviduct where fertilization will occur

  25. 2. Sperm Entry • Only ONE sperm is allowed to enter • Fast block - electrical charge in egg plasma membrane prevents polyspermy • Slow block - depolarization of egg plasma membrane due to Ca++ release

  26. 3. Egg Activation • The release of calcium ions in egg plasma membrane also triggers protein synthesis • 4. Fusion • The sperm nucleus is propelled to the egg nucleus by microtubules

  27. Let the Division Begin!

  28. Cleavage follows fertilization • Cleavage is a series of rapid mitotic divisions (without cell growth) • The two-celled zygote divides repeatedly until a ball of 32 cells is formed • This is the morula - 32 cells

  29. Continued divisions make the hollow blastula • These few cells are pluripotent (have the potential to become ANY of the 220 types of cells in the human body). • These are embryonic stem cells

  30. Development from Ovulation to Implantation

  31. Gastrulation • At the end of the cleavage stage, cells making up the blastula move about and surface proteins help cells recognize each other • The gastrula is formed, which consists of 3 “germ layers” • Endoderm • Mesoderm • Ectoderm

  32. Gastrulation

  33. Extraembryonic Membranes • These membranes develop from the germ layers, but are NOT part of the embryo (they are lost at birth) • They lie outside of the embryo & provide protection and nourishment • Four exist in terrestrial vertebrates: • Chorion, amnion, allantois (stores nitrogenous waste in reptiles), & yolk sac (not found in humans, but yolk aids in formation of RBC

  34. Human Development • The gestation period lasts 266 days from fertilization to birth • Organogenesis (development of the organs and organ systems) begins with the nervous system

  35. THANK YOU FOR YOUR ATTENTION

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