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Female cycle and pregnancy

Female cycle and pregnancy. Ovulation. When estrogen level is at its highest, it exerts positive feedback on the hypothalamus Which secretes GnRH Which causes a sharp increase in production of LH The surge in LH causes ovulation

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Female cycle and pregnancy

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  1. Female cycle and pregnancy

  2. Ovulation • When estrogen level is at its highest, it exerts positive feedback on the hypothalamus • Which secretes GnRH • Which causes a sharp increase in production of LH • The surge in LH causes ovulation • After this, negative feedback by estrogen and progesterone cause all 4 hormones to decline until menstruation finally occurs

  3. Pregnancy • If fertilization occurs, cycle is stopped and the developing zygote embeds itself in endometrium (implantation) • Layer of cells surrounding zygote releases HCG (human chorionic gonadotropic hormone) • HCG prevents disintegration of corpus luteum and causes it to secrete even more progesterone • Corpus luteum remains for up to 6 months

  4. Placenta • Originates from fetal and maternal tissue • Exchange of molecules between fetus and mother (blood doesn’t mix, instead things diffuse between mother and placental capillaries) • First 3 months of pregnancy: placenta forms • Produces HCG and estrogen and progesterone. These shut down anterior pituitary so no new follicles mature • They also maintain uterine lining • Pregnancy tests check for HCG

  5. Female sex hormones: estrogen • Stimulates growth of uterus and vagina at puberty • Secondary sex characteristics (breasts, hips, body hair, enlarged pelvic girdle) • Onset of menstrual cycle • Egg maturation • (both estrogen and progesterone required for breast development)

  6. Female sex hormones: Lactogenic Hormone (prolactin) • Needed for lactation to begin • Lactation begins several days after delivery (until then, colostrum is produces which increases protein and antibodies and decreases fat)

  7. Female sex hormones: Oxytocin • Released by posterior pituitary • Acts on uterus to cause contractions (along with prostoglandins) • Positive feedback: uterine contraction causes the release of more oxytocin, which in turn causes more contractions • Also: breastfeeding – when breast is suckled, nerve endings in areola are stimulated and the nerve impulses travel to hypothalamus, causing the posterior pituitary to release oxytocin (which causes milk letdown)

  8. Breasts • Mammary glands unique to mammals • 15 – 25 lobules with its own milk duct that begin at the nipples and divide into other ducts called alveoli

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