1. Implantation and Pregnancy

2. Our Goals this Section...
Describe the hormonal changes that occur as a result of implantation, including
production of human chorionic gonadotropin (HCG) to maintain the corpus luteum
increased production of progesterone by the corpus luteum
Describe a positive feedback mechanism involving oxytocin

3. Copulation & Fertilization
Up to 400 million sperm are ejaculated into the vagina
Sperm swim towards the ovaries
Ovum is only viable for 6-24 hours after ovulation
Fertilization usually occurs in the oviduct
Zygote begins to divide by mitosis

5. Implantation Dividing zygote moves towards the uterus
It becomes embedded in the endometrium wall (implantation)
Placenta develops from the embryonic and maternal tissues after implantation
Placental tissue secretes HCG (human chorionic gonadotrophin)
HCG maintains the corpus luteum

7. Pregnancy
Pregnancy has begun with the maintenance of the corpus luteum
Pregnancy Test detects HCG in urine
Corpus luteum continues to secrete estrogen and progesterone – continues until the placenta is fully developed
Placenta starts to secrete estrogen and progesterone

8. Pregnancy
Progesterone maintains the endometrium (prevents menstruation)
Estrogen inhibits FSH and LH from the anterior pituitary gland
Around 10 weeks the placenta is mature enough to produce enough estrogen and progesterone to continue the pregnancy
HCG diminishes and the corpus luteum will degenerate
Embryo continues to develop

10. Child Birth Average gestation is 40 weeks (9 months)
Uterus will contract a little throughout the pregnancy
Contractions become more severe in the late stages of pregnancy
False Labour – intermittent contractions
True Labour – sustained contractions

11. Child Birth Three Phases:
Dilation of the cervix
Birth of Child
Expulsion of afterbirth (placenta, etc)
Contractions of the uterus cause the posterior pituitary gland to secrete OXYTOCIN
Oxytocin intensifies the uterine contractions (positive feedback)