Embryo Folding Flashcards
In what directions does folding occur?
- Craniocaudal folding
2. Lateral folding
What occurs during craniocaudal folding?
Head and tail end come closer together, forms foetus position
What occurs during lateral folding?
Right and left sides come to fold and fuse in midline
What is lateral folding caused by?
Differential growth of the amniotic sac and yolk sac. The weight of the amniotic sac pushes down on the sides of the embryo causing the left and right sides to fold around the embryo
How does the growth of the amniotic sac compare to that of the yolk sac?
Amniotic sac grows rapidly, yolk sac remains almost same size
Why isn’t there fusion at the level of the midgut (bellybutton)?
As the yolk sac is in the way
What is this connection between the midgut and the yolk sac called?
Vitelline duct
What is the vitelline duct?
Tube within a tube - tube is within embryonic cavity, outer tube is amniotic cavity
Connection between yolk sac and midgut
What 2 layers does the lateral plate mesoderm split into?
Parietal/somatic and visceral/splanchnic
Above and below the level of the midgut, fusing occurs. What does this form?
Ventral wall
The amniotic cavity doesn’t completely fuse. What does this form?
Umbilical cord
What are Ectopia Cordis and Gastroschisis examples of?
Ventral Wall Defects
What happens during ectopia cordis?
Lateral folds fail to fuse in thoracic region (above level of midgut)
Leaves heart outside body walls (breastbone doesn’t form correctly)
What causes gastroschisis?
Lateral folds fail to fuse in abdominal region.
Leaves intestines outside body wall.
How is gastroschisis dealt with?
Intestines put in septic bag until baby grows enough to develop space for intestines
