Hormonal control of pregnancy


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Hormonal control of pregnancy

  1. 1. Hormonal control of pregnancy Nitin Pandey
  2. 2. Fertilization & Implantation Fertilization occurs at ampulla of the uterine tube
  3. 3. Steps of fertilization 1. Sperm are attracted to the ovum
  4. 4. Chemotactants, secreted by the ovary, attract sperm and interact with receptors in the sperm membrane. cGMP, formed by such activators of guanylyl cyclase as atrial natriuretic peptide (ANP) and nitric oxide , mediates an increase in the velocity and directionality of sperm movement, and it stimulates the acrosome reaction.
  5. 5. Steps of fertilization 2. Sperm bind to the zona pellucida
  6. 6. Once sperm are very close to the zona pellucida of the ovum, they undergo the acrosomal reaction. As a result of Ca2+ stimulation, as well as protein kinase C (PKC) and protein kinase A (PKA) activation, the acrosomal cap releases a corona-dispersing enzyme, a trypsin-like enzyme (known as acrosin), a neuraminidase, and hyaluronidases. Together, these enzymes disperse and digest the granulosa cells of the cumulus oophorus, and they permit attachment of sperm to the zona pellucida. The acrosomal reaction is stimulated by, and penetration of the zona is facilitated by, species-specific zona receptors. These receptors have oligosaccharide-binding sites for sperm membrane proteins, in particular one receptor that is termed ZP3
  7. 7. Steps of fertilization 3. Release acrosomal enzymes
  8. 8. Steps of fertilization 4. Fusion of membranes and entry of male pronucleus into ovum
  9. 9. Fusion sets off a reduction in the membrane potential of the ovum that prevents polyspermy, the fertilization of the ovum by more than one sperm. This transient potential change is followed by a structural change in the zona pellucida that provides protection against polyspermy on a more long-term basis.
  10. 10. Fertilization of ovum
  11. 11. Implantation ordinarily occurs on about the fifth to seventh day after ovulation Implantation results from the action of trophoblast cells that develop over the surface of the blastocyst These cells secrete proteolytic enzymes that digest and liquefy the adjacent cells of the uterine endometrium Progesterone helps in implantation by upregulating Synthesis of attachment molecule- integrin and osteopontin Implantation
  12. 12. A, Floating blastocyst. B, Attachment to the uterine epithelium and initial invasion of the syncytiotrophoblast cells.
  13. 13. The blastocyst penetrates deeper into the uterine stroma and develops an amniotic cavity.
  14. 14. The fully implanted embryo invades the maternal vasculature and the uterine epithelium grows over the implantation site and undergoes the decidualization
  15. 15. Failure to Reject the "Fetal Graft" placental trophoblast does not express the polymorphic class I and class II MHCgenes and instead expresses HLA-G, a nonpolymorphic gene. Fas ligand on the surface of the placenta, and this bonds to T cells, causing them to undergo apoptosis
  16. 16. Development and structure an of human placenta
  17. 17. Pregnancy is marked by the development of a unique organ, the placenta, which has a limited lifespan. This organ has diverse functions. It serves (1) as the fetal gut in supplying nutrients, (2) as the fetal lung in exchanging oxygen and carbon dioxide, (3) as the fetal kidney in regulating fluid volumes and disposing of waste metabolites, and (4) as a versatile endocrine gland that synthesizes many steroid and protein hormones that affect both maternal and fetal metabolism. Placenta
  18. 18. hCG and Human chorionic somatotropin
  19. 19. Foetus Mother uterus Placenta The MOTHER, PLACENTA, and FETUS acts as a unit to provide the optimal environment for fetal development Feto-placental unit Fetoplacental unit
  20. 20. Fetoplacental unit urinary estriol excretion of the mother can be monitored as an index of the state of the fetus.
  21. 21. Thank you
  22. 22. During pregnancy, the extreme quantities of estrogens cause (1) enlargement of the mother’s uterus, (2) enlargement of the mother’s breasts and growth of the breast ductal structure, and (3) enlargement of the mother’s female external genitalia. The estrogens also relax the pelvic ligaments of the mother, so that the sacroiliac joints become relatively limber and the symphysis pubis becomes elastic.These changes allow easier passage of the fetus through the birth canal. There is much reason to believe that estrogens also affect many general aspects of fetal development during pregnancy, for example, by affecting the rate of cell reproduction in the early embryo
  23. 23. 2. Progesterone decreases the contractility of the pregnant uterus, thus preventing uterine contractions from causing spontaneous abortion. 3. Progesterone contributes to the development of the conceptus even before implantation, because it specifically increases the secretions of the mother’s fallopian tubes and uterus to provide appropriate nutritive matter for the developing morula and blastocyst. There is also reason to believe that progesterone affects cell cleavage in the early developing embryo. 4. The progesterone secreted during pregnancy helps the estrogen prepare the mother’s breasts for lactation,