|
EMBRYOLOGY OF THE
ANTERIOR ABDOMINAL WALL
- WEEK 4
|
The embryo begins to fold and undergoes simultaneous longitudinal and
transverse growth.
- Cephalocaudal folding results
in the Yolk Sac being incorporated in the body of the embryo.
- Anterior embryo -
ectoderm forms foregut
- Tail of embryo -
ectoderm forms hindgut
- Intraembryonic section
of yolk sac located between foregut and hindgut = midgut
- Temporarily in direct
contact with yolk sac or vitelline duct (yolk stalk).
- Vitelline duct is
initially wide, but becomes narrow and elongated with further growth of
the embryo.
- Lateral folding of the
embryonic disc occurs at the same time as cephalocaudal folding. The flat
embryonic disc attains a round appearance at the junction between amnion
and ectodermal surface layer, and becomes located on the ventral aspect of
the embryo.
It has an oval shape and is known as the primitive umbilical ring, thus
forming the ventral ring.
4 wall folds form the ring:
- cephalic fold
- caudal fold
- lateral folds.