pregnancy. pregnancy (gestation) – carrying of developing young within the female reproductive...
Post on 04-Jan-2016
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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
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