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 anticipationof 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