Development of the foregut (esophagus and stomach

In this presentation the basic development of the Esophagus, Stomach, and Duodenum has been described.

1. DEVELOPMENT OF THE FOREGUT
(ESOPHAGUS AND STOMACH)
Dr.Sahar Hafeez
[email protected]
2014

2. Learning the Objectives
The students should be able to;

•Enlist the different parts of the foregut

•Describe the development of the Esophagus

•Describe the development of Stomach and its curvatures

•Describe the formation of Greater & Lesser omentum and the
Omental Bursa.

•Enlist the most common congenital anomalies of the Esophagus
and Stomach

3. Formation of the Primitive Gut
•The ‘cephalocaudal’ and
‘lateral’ foldings of the
embryo will lead to partial
incorporation of endoderm
lined cavity into the embryo
to form the “primitive gut
tube”.

•In the cranial & caudal ends
of the embryo the primitive
gut forms a blind ending
tube, the ‘foregut’ &
‘Hindgut’, respectively.

•The middle part of the tube,
‘Midgut’ remains
temporarily connected to
the yolk sac by means of a
vitelline duct/yolk stalk.

5. General consideration:
•As a result of embryonic folding, the
dorsal part of yolk sac is enclosed inside
the embryo to form the Gut.

•The gut is endodermal in origin, which
is surrounded by splanchno- pleuric
mesoderm.

•The Foregut is separated from the
stomodeum by the Buccopharyngeal
membrane.

•The Hindgut, is separated from the
proctodeum by Cloacal membrane.

•The Midgut is connected to definitive
yolk sac by Vittellointestinal duct.

6. Derivatives of the Foregut
•Oral cavity (tongue,
tonsils, salivary glands)
•Pharynx
•Esophagus
•Stomach
•Duodenum (Proximal half )
•Liver + Biliary apparatus
•Pancreas
Extent of Foregut
Foregut starts from the Oral cavity and
terminates at the level of Ampulla of
Vater (the point where common bile
duct opens into Duodenum)

7. Development of the Esophagus
•During the 4
th
wk., a small diverticulum appears in the ventral wall of
Pharynx.
•A ‘Tracheoesophageal Septum’ gradually separates the ventral
Respiratory diverticulum from the dorsal part of foregut.
• As a result, the Pharynx is divided into;
–a ventral portion the “respiratory primordium”,
–a dorsal portion, the “esophagus”.

8. Growth of esophagus

•Up to the 4
th
week it is very short.

•Then, it elongates rapidly due to
the descent of developing heart
and lungs.

•By the 7
th
week it reaches its final
position.

•Its lumen is completely or partially
obliterated due to proliferation of
its epithelial lining.

•Recanalization occurs by the end of
embryonic period (after 8
th
wk).

•Its muscles developed from the
surrounding mesoderm.

•It is striated in the upper 1/3,
• mixed in the middle 1/3 and
• smooth in the lower 1/3 (vagus)

9. Congenital malformations of Esophagus
Atresia of Esophagus & Esophageal Fistula:
•Mostly is the result of a spontaneous deviation of Tracheoesophageal
septum in the posterior direction
•As a result the proximal part of the esophagus ends as a blind sac, and the
distal part is connected to the trachea by a narrow canal just at the point
of tracheal bifurcation.
•Atresia of Esophagus prevents the normal passage of amniotic fluid into
the intestinal tract leading to the accumulation of excess fluid in the
amniotic sac (Polyhydroamnios)

10. Development of the Stomach
•Develops as a fusiform dilatation
of the caudal part of foregut in
the middle of 4
th
wk.
•Initially oriented in the midline.
•The swelling shows an expansion.
•During the next 2 weeks, the right
wall of the swelling grows more
rapidly than the left wall.
•This leads to the formation of
future ‘greater’ & ‘lesser’
curvatures of the adult stomach.
(The anterior/ventral border
becomes lesser curvature and the
posterior/dorsal border becomes
greater curvature)

11. Rotation of Stomach
Longitudinal axis:
•As the stomach enlarges, it slowly rotates 90⁰ (clockwise) around its
longitudinal axis. As a result;
•The ventral border moves to the right & the dorsal border moves to the left
•The original left side becomes ventral surface & the original right side
becomes dorsal surface ( grows faster than the ventral surface)

12. In Transverse/Horizontal
axis:
•The rapidly growing
dorsal/posterior wall of
stomach slightly rotates the
stomach on the transverse
plane
•As a result, the cranial
(esophageal) end of
stomach moves down & to
the left, while, the caudal
(duodenal) end moves up
and to the right.

13. Formation of the Lesser sac/Omental Bursa
•During its development, the stomach is
suspended in the midline with the help of
double-layered mesenteries
(mesogastrium),
•the Dorsal mesogastrium connects it to
the posterior/dorsal body wall.
•The Ventral mesogastrium attaches the
gut tube to the anterior abdominal wall
•Rotation around the longitudinal axis pulls
the ‘dorsal mesogastrium’ to the left.
•This move leads to the formation of
‘Omental Bursa’ (a pouch of peritoneal
cavity located behind the stomach).

14. Formation of Greater & Lesser Omenta
•With the rotation of stomach in
transverse/horizontal axis, the
greater curvature along with the
attached double-layered dorsal
mesogastrium also comes to lie
transversely.
•This mesogastrium hanging from
the greater curvature covers the
coils of intestine like a curtain & is
known as ‘Greater Omentum’

•A small part of the ventral
mesogastrium which is lying
between the lesser curvature of
stomach & the inferior surface of
liver is known as ‘Lesser
Omentum’

15. Congenital Malformation of Stomach
Pyloric Stenosis:
•Sometimes the circular or
longitudinal musculature of the
stomach in the region of the
pylorus is hypertrophied.

•One of the most common
anomalies in newborns

•Treatment: Surgical excision of the
thickened sphincter.
Projectile vomiting

16. Development of the distal part of Foregut (Duodenum)
With the 90⁰clockwise rotation.
the greater posterior wall of
stomach moves to the left in
abdomen & the C-shaped
Duodenum moves to the right.

17. Blood supply of the derivatives of Foregut:

•Celiac trunk is the branch of dorsal aorta which supplies all the
derivatives of developing foregut.