Pregnancy & Development
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What are the stages of pregnancy?
- Embryonic Development
- Fetal Development
What happens during fertilization?
- Egg is viable 12 - 24 hours
- Sperm is viable 12 - 48 hours
- Sperm make their way to uterine tube, oocyte pulls in head of sperm, not allowing a second sperm to enter, then undergoes division.
- Fertilization happens when genetic materials form a zygote
What is a zygote?
First cell of a new individual, resulting from fusion of genetic material between oocyte and sperm, that rapidly undergoes mitotic division while in the uterine tube moving toward the uterus
What is an embryo?
- Developmental stage from cleavage - 9th week
- Embryo enters uterus at 16 cell state
- Temporarily floats free in the uterus
- Nourished by uterine secretions
What is the blastocyst?
Ball-like circle of around 100 cells consisting of a trophoblast - large fluid filled sphere, and an inner cell mass, that secretes hCG
What are the 3 germ layers of the blastocyst?
- Ectoderm - Outside layer, becomes nervous system and epidermis
- Mesoderm - Middle layer, becomes mucosae and glands
- Endoderm - Inside layer, becomes everything else
What does the placenta do?
- Delivers nutrients and oxygen
- Forms barrier between mother and embryo
- Removes waste from embryonic blood
- Produces hormones
What is the fetus?
- Baby at beginning of 9th week
- All organ systems are formed
- Tremendous growth and change in appearance
What are the physiological changes of pregnancy on the mother?
- Body water rises
- Blood volume increases 25 - 40 percent
- Blood pressure and pulse increase
- Varicose veins common
What happens during childbirth (partition)?
- Labor - estrogen rises, contractions, Oxytocin released, prostaglandins
- Dilation - Cervix dilates, contractions increase, amnion ruptures
- Expulsion - Infant passes through cervix and into vagina
- Placental - Delivery of placenta
How is gender determined?
- At fertilization:
- XX Female
- XY Male
- Gonads form in 8th week
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