CHAPTER 22: THE REPRODUCTIVE SYSTEMS
VII.HORMONES OF PREGNANCYSee Fig 22.37 and 22.38, page 917.
A.Estrogens and Progesterones:
1.from corpus luteum through month 3:
a.relatively low levels;
b.maintain uterine lining during pregnancy (i.e essentially needed for the continued attachment of the embryo/fetus.)
c.prepare mammary glands to secrete milk.
2.from placenta (chorion) from month 3 until birth:
a.extremely high levels;
c.develop mammary glands for lactation.
2.Human Chorionic Gonadotropin (hCG) from chorion of placenta:
1.stimulates continued secretion of estrogens and progesterones by the corpus luteum (mimics LH);
2.can be detected by Day 8;
3.peaks at about Week 9;
4.decreases sharply during fourth and fifth month;
5.may be the cause of "morning sickness".
C.Human Chorionic Somatomammotropin (hCS) or Human Placental Lactogen (hPL) from chorion:
1.secretion starts about Day 8;
2.Levels increase as size of placenta increases;
3.peaks at Week 32 and remains at that level;
a.development of breast tissue for lactation;
b.deposition of protein in tissues;
c.regulation of metabolism:
decreases use of glucose by mother, leaving more available to fetus;
releases fatty acids from fat deposits, providing an alternative source of energy for the mother's metabolism.
D.Relaxin from the placenta and ovaries assists in delivery.
1.relaxes pubic symphysis and ligaments;
2.dilates uterine cervix.
E.Inhibin from the ovaries:
1.inhibits secretion of FSH.