PREGNANCY

Pregnancy

• (gestation) – carrying of developing young within the female reproductive tract

• Fertilization to birth

• Humans = 266 days (38 weeks)– (actually doctors measure 40 weeks because

they start from the last menstrual cycle)

• About 1 week after conception, the embryo (blastocyst) implants in the endometrial wall of the uterus

• Stem cells – give rise to every type of cell in the body (inner cell mass)

• Trophoblast – outer cell layer, becomes part of the placenta• Placenta – organ that provides nourishment and oxygen to the

embryo, also gets rid of metabolic waste

After Implantation: 4 pieces of life support1. Amnion – fluid filled sac that encloses and

protects the embryo, breaks just before birth2. Yolk Sac – contains no yolk, produces embryos

first blood and germ cells (gamete forming cells)3. Allantois – forms part of the urinary bladder and

part of the umbilical cord (life-line between embryo and placenta)

4. Chorion – part of the placenta, maintains high levels of estrogen and progesterone in mom’s blood…why?

• No new follicles mature• Prevents menstruation

Placenta…

• Contains chorionic villi – embryonic blood vessels that are in close contact with maternal blood supply

• Mom’s blood and embryo’s blood do not mix.• By diffusion, nutrients, oxygen, antibodies,

viruses (German measles), and drugs move from mom to embryo and waste moves from embryo to mom