Human Anatomy and Physiology Pregnancy, birth and nutrition of young

Pregnancy Sperm reach egg (30 min.) Sperm highly motile Prostaglandin in semen causes uterus and fallopian tubes to contract towards egg Female aids sperm movement Estrogen causes differential fluid pressure in reproductive tract Estrogen decreases cervical mucus

Sperm survival Factors decreasing survival Leakage from vagina Acidity of female tract

Fertilization Sperm capacitation Acrosomal enzymes weaken oocyte membrane Sperm nucleus and centriole penetrates into the ovum Monospermy is assured by: Entry of extracellular Na + reversing oocyte membrane polarity Ca ++ causes cell to prepare for cell division This cortical reaction destroys sperm receptors on plasma membrane of the egg

Early development Fertilized embryo takes 7 days to implant Nutrients provided by wall of fallopian tube By week 8, placenta is formed and serves as the organs

Hormones Viability of the corpus luteum maintained by hCG Levels of estrogen and progesterone rise due to secretion by the placenta Estrogen and progesterone levels rise in anticipation of birthing and lactation

Birthing Involuntary contractions of uterine smooth muscle (positive feedback)

Birthing Amniotic sac pushes up against cervix wall (“breaking of water”) Birth follows Further uterine contraction expels the placenta

Lactation Rising estrogen and progesterone levels stimulate release of PRH Lactogenesis Colostrum is the first milk Little fat, mostly protein, vitamins, IgA antibodies

Milk let down reflex Positive feedback (galactopoiesis)

Female pill Estrogen and progesterone in high doses inhibit ovulation because hypothalamus fails to secrete luteinizing hormone Low doses alter egg transport time in fallopian tube preventing implantation abnormal development of endometrium abnormal cervical mucus: lethal to or blocks entry of sperm abnormal contraction of fallopian and uterine musculature