PREGNANCY The presence of a developing offspring in the uterus. Fertilization: egg + sperm=zygote Occurs in uterine tube Ectopic/Tubal pregnancy: zygote does not drop into uterus

Early embryonic development Zygote undergoes mitosis, giving rise to smaller and smaller cells during cleavage. (30 hrs) Morula (16 cells) moves down uterine tube and implants in endometrium. Once implanted, the offspring is called an embryo through week 8. Fetus week 8-40. Placenta forms from cells of embryo and endometrium. Organ of exchange of nutrients, gases, and wastes b/w maternal blood and embryo blood Secretes hormones

Hormones hCG (human chorionic gonadotrophic) Prevents pregnancy loss Relaxin Relax ligaments of pelvic joints Inhibit contraction of uterus Estrogen & progesterone Maintain uterine wall and inhibit secretion of FSH and LH

Embryonic stage Week 2-8 Placenta and main internal and external body structures develop Amnion (membrane w/in placenta) develops around embryo Amniotic fluid fills the space b/w amnion and embryo Umbilical cord forms from amnion - suspends embryo in cavity -exchange blood b/w embryo and placenta -contains 2 arteries and 1 vein End of week 8 embryo is recognizable as a human

MONTH 2 MONTH 5 MONTH 3 MONTH 7 MONTH 4

Fetal Stage Week 8-birth Fetus is full term after 38 weeks MONTH 9

Milk production Birth process Decrease in progesterone initiates birth process Pituitary gland releases oxytocin to stimulate uterine muscles to contract Afterbirth (placental tissues) are expelled following birth Milk production Hormone prolactin stimulate mammary gland to produce milk Colostrum: substance first released from gland that contains proteins and antibodies

Twins Fraternal: 2 different eggs and 2 different sperm Results in 2 genetically different offspring Identical: Fertilized zygote slits during cleavage Results in 2 genetically identical offspring