Pig Dissection
#1 Fetal Development
And the Umbilical Cord
Producers of Shelled Eggs
• Bird Egg?
• Reptile Egg?
• Monotreme Egg?
Shelled egg structures
•
•
•
•
•
Germinal spot = “egg”
Yolk = fat; energy
White (albumen) = protein; structure
Shell
Air space
Shelled Egg Membranes
• Chorion – thin membrane
that presses close to the
shell; creates air space;
allows gas exchange
• Yolk sac – engulfs yolk;
food source
• Allantois – storage sac for
waste; allows gas
exchange
• Amniotic sac – contains
amniotic fluid; cushion,
moisten, shock absorber
Human embryos
• Develop all shelled
egg membranes
• Some take on new
roles – ie. Help
develop the placenta
Human embryo amnion and yolk
sac
Other embryonic evolutionary
“left-overs”?
• Fetal tail
• Fetal gill
arches
Placenta development
• Fertilization occurs
where?
• Fallopian tube
• Mitosis begins; 5 – 10
days later embryo
arrives in uterus
• Chorion begins to
embedd in
endometrium lining of uterus
Human Female Reproductive
Anatomy
Embedding Embryo
Placental Formation
• Chorion begins to grow villi into uterine
lining
• Allantoic and yolk sac blood vessels begin
to form umbilical cord
• Chorion begins to release HCG –
human chorionic gonadotropin
hormone that maintains the developing
placenta in the uterus
• Effect on the uterine lining?
• Missed period
• HCG detected in pregnancy urine test
• Later, placenta makes its own hormones to
maintain itself (progesterone)
Fetal Development
Late Term Fetus
Amniocentesis
•
•
Needle used to
sample amniotic
fluid for diagnostic
purposes
Done at 14 – 16
weeks
Chorionic Villi Sampling
• CVS
• Sample of placenta
taken for
diagnostic
purposes
• Done at about 10
weeks
Umbilical Cord
•
•
•
•
•
•
Forms partially from old allantoic and yolk
stalks – using their blood vessels
Connects fetal blood to the placenta
Placenta contains maternal blood
Cord – contains 2 umbilical arteries and 1 umbilical vein
Arteries – **carry blood away from a reference point**
Reference point: fetus
**Usually carry oxygenated blood**
Exception: these 2 umbilical arteries
carry deoxygenated blood from baby to mom
Veins - **carry blood toward a reference point**
Reference point: still fetus
**Usually carry deoxygenated blood**
Exception: the umbilical vein carries oxgenated blood from mom to baby
Fetal Circulation
Oxygenated
blood
Deoxygenated
blood
Placenta
• Umbilical arteries
branch into small
capillaries at the
placenta
• Diffusion occurs
across capillary walls
from baby to mom
• What diffuses?
• CO2, waste (urea)
• Mom’s lungs and
kidneys excrete
Placental Detail
Placental Detail
Placental Blood Exchange?
•
•
•
•
Does fetal blood mix with maternal blood?
NO!! Why not?
Separated by capillary wall
Only diffusion occurs
Placental Detail
• What diffuses from mom’s blood to baby?
• Food, minerals, vitamins, O2, antibodies,
water, drugs, cigarette chemicals
• Carried back to fetus by umbilical vein
• Blood enters the fetal liver prior to the
fetal heart and general circulation
• Ideas why?
• Detoxify and store glucose
Cross Section View of the Umbilical
Cord – “Live” Fetus
Cross Section View of the Umbilical
Cord – “Dead” latex injected fetus
Human Female Reproductive
Anatomy
Animal bihorned uterus
• Uterus split into 2
parts (horns)
• Allows for multiple
embryos