MCB 135 E

1. MCB 135 E Discussion 2 September 13-17, 2004

2. Physiology of Human Development • GSI – Jason Lowry • E-Mail – Jlowry@Berkeley.Edu • Office Hours – Thursday 1-2pm in 208 Donner • Discussions: • Thursday 11-12 in 130 Wheeler • Friday 2-3 in 219 Dwinelle • Material covered is similar for each discussion • Reviews • An organized review will be given prior to each mid-term and the final • Times and Locations to be announced

3. Fertilization • Reproductive Techniques (Web-Site) • Terminology • Stages of Fertilization • Roles of Ovum • Roles of Sperm

4. Fertilization – Formation of zygote Capacitation – Changes that occur between sperm and ovum to allow only one sperm to successfully penetrate the ovum (Increase fertilizing capacity) Cleavage – Mitotic division of the zygote into a morula Morula – Ball of cells that will form blastula that will implant in uterus Zygote – Union of female and male sex cells into a combined cell Terminology

5. Stages of Fertilization • Penetration • Random contact between sperm and egg • Sperm propel past corona cells and attach to zona pelucida • One sperm-One Egg • Activation • Completion of Meiosis of ovum – forms female pronucleus • Sperm Changes – Sperm travels toward center of egg, head swells, becomes male pronucleus • Rearrangement in egg – biochemical changes necessary prior to nuclear fusion • Nuclear Fusion • Union of two pronuclei • Loss of nuclear envelope, contribution of chromosomes to first mitotic cleavage

7. Roles of Ovum • Contribute maternal complement of genes to the nucleus of the fertilized egg • Reject all sperms but one • Provide food reserves until the embryo begins to feed upon exogenous material

8. Roles of Sperm • Reach and penetrate egg • Activate the egg to nuclear and cytoplasmic division necessary to embryonic development • Contribute the paternal complement of genes to the nucleus of the fertilized egg

9. Results of Fertilization • Reassociation of male and female sets of chromosomes to full diploid number • Physical basis for inheritance and variation • Determination of sex • Activation of ovum into cleavage

10. Implantation • Terminology • Sequence of Events • Changes necessary for implantation • Time Course

11. Terminology • Implantation – Process of preparation of the uterine zone for blastocyst embedding and the active penetration of this zone by the blastocyst • Nidation – Latin for nest (alternate name for implantation) • Blastocyst – Approximately 60 cells stage where morula has become fluid filled • Of the cells, about 5 clump together to form inner cell mass (ICM) that projects into blastocele

12. Implantation Events • Days 1-8 • Fertilized egg begins to divide by cleavage into smaller blastomeres • Blastomere increase follows a double synchronous sequence initially, but later becomes asynchronous • Later stage cleavage forms a ball of cells or morula • Fluid begins accumulating in morula and a conversion occurs to the blastula (blastocyst) • Blastocyst attaches to uterine stroma • Outer layer of cells begin to proliferate and invade stroma of uterus

13. Implantation Events • Days 8-16 • Blastocyst lodged in uterine stroma • Trophoblast (outer cells) invades uterine stroma and begins to form placenta • Blastocele becomes chorionic cavity • Inner cell mass begins to proliferate and form germ disc and primitive entoderm • Complex sequence of chemical and physical interactions occur between ovum and mother • Only about 50% of fertilized eggs successfully implant

14. Uterine Preparation • Estrogen • Involved in proliferation of uterus (hypertrophy) • 3-5 Days post-ovulation E dominates and is thought to play a role in transport of ovum • Progesterone • Increased Vascularization (hypervascularization) • 5-7 days post-ovulation, P increases and counters the effect of E thus relaxing uterine contractions • hCG • Prevents corpus luteum regression • Similar to LH • Maintains E+P during early embryonic development

16. Embryonic Development • Terminology • Germ Layer Theory • Embryonic Stages • Germ Layers and Their Systems

17. Terminology • Germ Layer Theory • Embryo’s Method of sorting out its parts • Ectoderm – Outer covering of embryo • Entoderm (Endoderm) – Lies under the ectoderm and forms lining of the primitive gut cavity • Mesoderm – Develops between ectoderm and entoderm • Gastrulation – The process by which germ layers come to occupy their characteristic positions • Embryonic Stages – Phases of gastrulation; stages of organ and tissue differentiation

18. Embryonic Stages • Early Gastrulation • Occurs at implantation when cells on ICM arrange into the entoderm • Remaining cells that are neither trophoblast or entoderm become a plate containing the progenitors of future ectodermal and mesodermal cells • Referred to as 2-layered embryo and characterized by embryonic disc

19. Embryonic Stages • Late Gastrulation (second phase) • Segregation of mesoderm and notochord occurs • Notochord will for primitive vertebral column • Starts by end of second week and finishes by end of third week • 2-layered embryo becomes 3-layered embryo • Primitive streak appears upon upper surface of embryonic disc over which mesoderm spreads • At conclusion of this process, upper layer of embryonic disc becomes ectoderm

21. Germ Layers and Their Systems • Ectoderm • Epidermis and lining cells of glands • Appendages of skin • Nervous system • Posterior Pituitary • Chromafin organs - adrenal medulla • Anterior Pituitary • Some Epithelium • Entoderm • Epithelial lining of alimentary canal • Lining cells of glands that open to alimentary canal • Epithelium of most of the urinary bladder and urethra • Epithelium of prostate • Mesoderm • Remaining organs and tissues not made by Ectoderm or Entoderm • Connective tissue • Teeth • Musculature • Blood • Adrenal Cortex