Fertilization At fertilization, zygote forms protective coating to keep other sperm out Divides to become…. Blastocyst, which attaches to lining of uterus during implantation (1 week)

Some cells divide to become… Support structures: Placenta- Provides oxygen, nutrients, and water by diffusing molecules across membranes between mom and baby’s blood Umbilical cord- Transports nutrients to baby and waste to mom Amniotic sac- Protects baby and keeps at correct temperature for growth

8 Weeks in Utero

12 Weeks in Utero

Other cells divide to become: The embryo (early development), which divides into three tissue layers Stem cells- can make any one of 220 different body cells

3 Tissue Layers Differentiate Respiratory and digestive systems Muscles, bone, blood vessels, skin Nervous system, sense organs, mouth

Fetus Becomes fetus after 8 weeks of development All organs are in place, but need to further develop Head develops at 9 weeks Fetus begins to move at 5 months (mom feels) Eyes open at 7 months Fetus moves into head-down position and ready for birth at 9 months (37-40 weeks) 12-14 week fetus model

Pre-Labor Irregular contractions from upper part of uterus Mucus plug sealing cervix is discharged (bloody show) Amniotic sac ruptures and discharges water

3 Stages of Labor 1- Cervix dilates 10 cm & effaces (thins) 2-Baby born (7- 7/12 lbs, 19-21 inches) 3- Placenta, umbilical cord, sac pushed out (Afterbirth)

Incision into abdomen to remove baby Cesarean Section Incision into abdomen to remove baby 25-33% of births in U.S. are C-Section Why? Hips too narrow Baby in distress Umbilical cord wrapped around neck Vaginal infections Placenta previa Baby in breech position Women may have up to 3-4 c-sections

Breech Presentations

Twins Identical vs. Fraternal Identical- one egg fertilized by one sperm, copies and splits (must be same sex) Fraternal- two eggs fertilized by two sperm