Pregnancy

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Pregnancy Development
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Fertilization

• Timing (egg good for 12-24 hours sperm good
  for 48-72 hours)
• Oviduct
• Capacitation enables sperm to fertilize ovum
• Sperm numbers about 50 work on the egg

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Fertilization

• Diploid
• Zygote
• Sex determination
• Twins
• Dizygotic (fraternal)
• Monozygotic (identical)

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Cleavage

• 30 hours to 4 days
• Mitosis
• Oviduct
• Morula

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Blastocyst Stage

• Day 5
• Uterus
• Rearrangement of cells
• Trophoblast cells will become placenta
• Inner cell mass will become fetus
• Implantation day 7 or 8

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Gastrulation

• Week 2
• Ectoderm destined to become nervous tissue and
  skin
• Mesoderm destined to become skeleton, muscles,
  heart, blood vessels
• Endoderm destined to become gut lungs

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Neurulation

• Week 3
• Embryo is 2mm long (pencil eraser size)
• Neural groove
• Neural tube
• Destined to become brain and spinal cord

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Organogenesis

• Week 4
• Embryo 5 mm long
• All major organs have begun their formation
• Arm Leg buds form
• Thalidomide German Measles examples of what can
  go wrong.

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Fetus

• By end of third month, embryo is distinctly human
• All major organs are established
• Growth for second and third trimester

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Maintenance of Endometrium

• Estrogen Progesterone
• From corpus luteum early
• From placenta later
• Birth control pills

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Human Chorionic Gonadotropin

• HCG
• Made by embryo
• 2-12 weeks
• Maintains corpus luteum through first trimester

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Placenta

• Development begins at 4 weeks and functional by
  12 weeks
• Covers about 1/3 of inner uterus
• Function
• Nutrients
• Waste
• Estrogen Progesterone

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Placenta

• Maternal tissue
• Decidua basalis of the endometrium
• Fetal tissue
• Chorion which develops from the trophoblast cells
• Chorionic villi contain capillary beds from
  umbilical arteries and vein

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Fetal tissue

• Umbilicus
• Amnion
• Amniotic fluid

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Gestation

• 280 days
• 9 full months

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Parturition

• Mild contractions due to high levels of estrogen.
• Once contractions occur every 30 minutes, labor
  occurs
• Amniotic fluid released
• Babys head serves as a wedge

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Hormones

• Estrogen increases which causes uterine
  contractions, then levels drop as parturition
  proceeds
• Progesterone levels drop allowing the uterine
  contractions
• Local prostaglandins result in contractions

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Hormones

• Oxytocin causes strong uterine contractions and
  works in a positive feedback mechanism
• Relaxin, made by placenta, dilates cervix,
  relaxes symphysis pubis

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Afterbirth

• 10-45 minutes later
• Placenta