Fetal Development

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Fetal Development Labor and delivery Chromosomal
abnormalities
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After implantation, cells of blastocyst start
to differentiate into three germ
layers Ectoderm- skin and nervous
system pituitary gland Mesoderm- connective
tissue and muscle endocrine, cardiovascular,
skeletal systems Endoderm- digestive,
respiratory, urinary, reproductive systems
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By blastocyst
By placenta
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Extraembryonic membranes Start forming after
implantation Yolk sac- trasnport of nutrients,
red blood cell formation. Role reducedgt 6
weeks Amnion- encloses amniotic cavity. Fluid
cushions developing embryo/fetus Allantois-
forms urinary bladder umbilical cord Chorion-
blood vessels help nourish embryo develops into
placenta
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Placenta Umbilical arteries and veins provide
fetal circulation Maternal circulation does not
actually mix with fetal blood Gas and nutrient
exchange takes place here Secretes estrogen and
progesterone to maintain endometrium
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Four weeks
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8 weeks
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Labor and childbirth Labor oxytocin
(hypothalamus) prostaglandins Fetal adrenal
gland produces cortisol and an estrogen
precursor makes uterus more sensitive to
oxytocin and prostaglandins CRH secretion by
placenta triggers fetal adrenal gland activity
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Developmental defects Aneuploidy (wrong number
of chromosomes) Karyotyping- chromosomal
analysis Down syndrome- trisomy 21 Edwards
syndrome- trisomy 18 Patau syndrome- trisomy
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Abnormal number of sex chromosomes XO- Turner
syndrome XXY- Klinefelter syndrome XYY
syndrome Arises due to mistakes in
meiosis Developmental problems- spontaneous or
due to exposure to harmful substances (teratogen
s)
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Proper fetal development depends
on Nutrition Freedom from infection Avoidance
of drugs and alcohol Avoidance of
smoking lowers vitamin levels substances in
smoke can cross placental barrier
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Development does not stop at birth! Neonate-
rapid growth and neurological development Pubert
y- sexual maturation Secondary sexual
characteristics Aging-?
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Contraception- prevention of pregnancy Sterilizat
ion Abstinence Hormonal (birth-control
pills) male pill? Anti-implantation Barrier
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Infertility Artificial insemination Egg
donation Embryo transfer In vitro
fertilization Intrafallopian transfer
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Summary

• Progression from gametes to zygote to
  multicellular organism
• Development, labor and delivery under hormonal
  control
• Aneuploidy leads to serious developmental defects
• Development does not stop at birth