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DEVELOPMENT OF FOREGUT
DR NEETA CHHABRA
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Introduction
• Development of alimentary tract: Alimentary tract develops from
the primitive gut.
• Primitive gut is formed due to incorporation of dorsal part of
definitive yolk sac within the embryo when the embryo gets
folded on itself at the caudal and cranial ends and also due to
lateral folding
• It communicates with
• Yolk sac through the vitellointestinal duct.
• Allantoic diverticulum.
• It is closed anteriorly by buccopharyngeal membrane which
separates it from stomodeum Posteriorly it is closed by cloacal
membrane which separates it from proctodeum.
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3.
Introduction
Primitive gut has 3 parts:
• Foregut : Cranial part of the gut that lies in the head
fold
• Midgut: Part of gut that communicates with
vitellointestinal duct
• Hindgut: Caudal part of gut that lies in the tail fold
• Anterior intestinal portal: Communication between
foregut and midgut
• Posterior intestinal portal: Communication between
midgut and hindgut.
• Vitellointestinal duct disappears by 5th week
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Foregut
Extent: From the Oral cavity to a point where common bile
duct opens into Duodenum
Derivatives
1. Pharynx and its derivatives ( oral cavity, pharynx, tongue,
tonsils, salivary glands and upper respiratory system
2. The lower respiratory system
3. Oesophagus and stomach
4. Duodenum, proximal to the opening of the bile duct
5. Liver, gallbladder , extrahepatic biliary apparatus
6. Pancreas
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Midgut
Extent: From the opening of bile duct in duodenum to the
junction of right 2/3rd and left 1/3rd of transverse colon
Derivatives
1. Duodenum beyond the opening of common bile duct
2. Jejunum
3. Ileum
4. Appendix
5. Cecum
6. Ascending colon
7. Right colic flexure
8. Right 2/3 of transverse colon
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Hindgut
Extent: From the junction of right 2/3rd and left 1/3rd of transverse
colon to the upper part of anal canal
Derivatives
1. Left 1/3 of transverse colon.
2. Left colic flexure.
3. Descending colon.
4. Sigmoid colon.
5. Rectum.
6. Upper ½ of anal canal.
7. Primitive urogenital sinus derivatives.
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Mesenteries of GIT
Gut is attached to body wall by the ventral and dorsal
mesenteries.
• Ventral Mesentery: Exists only in the terminal part of
oesophagus, stomach and upper part of duodenum. Growth of
liver divides it into
• Lesser omentum
• Falciform ligament
• Dorsal Mesentery: Suspends the caudal part of foregut,
midgut & a major part of the hindgut from the abdominal wall.
It forms:
• Dorsal mesogastrium
• Dorsal mesoduodenum
• Dorsal mesentery of jejunal & ileal loops (Mesentery proper)
• Dorsal mesocolon 7

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Blood supply of GIT
• Dorsal to the gut tube lies the Dorsal Aorta.
• It gives off a large no of ventral branches
called vitelline arteries. Most of these
disappear and only 3 remain
• Coeliac trunk: supplies the foregut
• Superior Mesenteric artery: supplies the
midgut
• Inferior mesenteric artery: supplies the
hindgut .
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9.
Development of Oesophagus
• Develops from the part of foregut between the
pharynx and stomach.
• Stages of Development
• At 4th wk of IUL :Tracheobronchial or
respiratory diverticulum appears in the ventral
aspect of foregut at the caudal end of
pharyngeal foregut.
• Soon Tracheoesophageal fold and septum
develops which divides it into two parts: ventral
trachea and dorsal oesophagus.
• Initially oesophagus is short but elongates due to
the formation of neck and descent of the
diaphragm, lungs and heart.
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10.
Histogenesis of Oesophagus
• Endoderm of foregut: Forms the Epithelium &
gland
• Splanchnopleuric mesoderm surrounding the
foregut: Forms the muscles and connective
tissue
• Muscular coat of oesophagus is made up of
• Striated muscles in upper 1/3
• Mixed coat in middle 1/3
• Smooth muscles in lower 1/3
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Anomalies of Oesophagus
• Oesophageal atresia: due to deviation of
tracheooesophageal septum in a posterior
direction or Failure of recanalisation of the
oesophagus.
• Oesophageal stenosis: Due to incomplete
recanalization of oesophagus. Polyhydramnios
• Tracheoesophageal fistula: Communication of
trachea with oesophagus
• Achalasia cardia or cardiospasm: Failure of
muscular relaxation in lower part of
oesophagus due to loss of ganglionic cells in
Auerbach’s plexus.
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12.
Development of Stomach
• Stomach develops during 4th–5th week as a
fusiform dilatation of the part of the foregut
distal to the oesophagus.
• Fusiform sac has left and right surfaces and
ventral and dorsal borders.
• Due to differential growth, Dorsal border grows
more.
• It forms the fundus and greater curvature of
stomach.
• Ventral border grows slowly and forms lesser
curvature.
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• Rotation of stomach takes place in a clockwise
direction (around 90°) both along the longitudinal
axis & transverse axis
• Rotation along longitudinal axis : Left surface
becomes the anterior surface and the Right surface
becomes the posterior surface.
• This explains why the anterior surface is supplied
by left vagus nerve and posterior surface by right
vagus.
• Rotation along anteroposterior axis : Lower or
pyloric end faces upwards and to the right.
Upper or cardiac end faces downwards and to the
left.
Rotation of Stomach
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Mesenteries of Stomach
• Ventral mesogastrium : attached to the ventral border,
attaches it to septum transversum
• Dorsal mesogastrium : attached to dorsal border,
attaches it to dorsal body wall
Liver develops in ventral mesogastrium & divides it into
• Lesser omentum : Between liver and stomach
• Falciform ligament : Between liver and anterior
abdominal wall
Spleen develops in dorsal mesogastrium & divides it into
• Gastrosplenic ligament: Between greater curvature of
the stomach (fundus) and spleen
• Lienorenal ligament : Between spleen & posterior body
wall
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Formation of Lesser sac (Omental bursa)
• Omental bursa is a space behind the
stomach
• It is formed when dorsal mesogastrium
is pulled to the left as a result of rotation
of stomach around longitudinal axis.
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Formation of Greater Omentum
• The dorsal mesogastrium from rest
of the greater curvature extends
downwards to form a double layered
fold of peritoneum called Greater
omentum.
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Anomalies of Stomach
• Congenital Hypertrophic Pyloric Stenosis:
Hypertrophy of circular muscle layer at pylorus
More common in males
Characterized by progressive vomiting
Treatment: Surgical correction.
• Duplication of Stomach
• Presence of prepyloric septum
• Thoracic stomach: Oesophagus is short and the
stomach is displaced in the thorax through the
oesophageal opening
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Development of Duodenum
Duodenum develops from two sources:
• 1st part & 2nd part up to the opening of CBD: Foregut
(Supplied by branches of Coeliac trunk)
• 2nd part beyond opening of CBD, 3rd & 4th part: Midgut
(Supplied by branches of Superior Mesenteric artery)
• Duodenum is attached to the dorsal body wall by
mesoduodenum
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• Primitive duodenum is in the form of a loop with a
ventral convexity in the median plane. It is attached
to the posterior abdominal wall by mesoduodenum
• When the stomach rotates , the duodenal loop
rotates to the right and the mesoduodenum fuses
with the peritoneum of posterior abdominal wall.
Later both of them disappear.
• By the end of the embryonic period duodenum
becomes retroperitoneal except near pylorus of
stomach where a small portion of duodenum
remains intraperitoneal ( duodenal cap)
Development of Duodenum
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Anomalies of Duodenum
• Duodenal atresia: Complete occlusion of lumen.
Produces polyhydramnios.
• Duodenal stenosis: Partial occlusion
Bile stained vomiting
• Duodenal diverticula: usually arises from the
second part of the duodenum.
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• Liver develops from the following sources:
• Endodermal liver bud forms the hepatocytes
and intrahepatic biliary apparatus.
• Septum transversum forms connective tissue
of liver including fibrous capsule, Kupffer’s cells
and blood vessels.
• Vitelline and umbilical veins form sinusoids.
• Ventral mesentery forms lesser omentum ,
falciform, coronary and triangular ligaments.
Development of Liver
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Development of Liver
Stages of development
• Formation of hepatic bud: During the 5th week of
IUL, hepatic bud arises from terminal part of
foregut.
• It grows in ventral mesogastrium and divides into
cranial pars hepatica and smaller caudal pars
cystica.
• The pars hepatica reaches the septum
transversum and divides into right and left
hepatic branches
• Each hepatic branch forms solid cord of cells
called hepatic trabeculae which form the two
lobes of liver
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Development of Liver
• The hepatic trabeculae differentiate into solid plates of
liver cells which form liver parenchyma and lining of
biliary canaliculi
• The vitelline and umbilical veins lying in the septum
transversum break up into a capillary network and
form Hepatic sinusoids
• The mesenchyme of the septum transversum form
Haematopoietic cells
Kupffer’s cells
Connective tissue cells
Blood vessels
Capsule of the liver
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Development of Gallbladder & Biliary Apparatus
• Gall bladder and cystic duct develops from Cystic bud
• The right and left branches of the pars hepatica become
canalized to form the right and left hepatic ducts
• The hepatic ducts join to form Common hepatic duct
• The common hepatic duct and cystic duct join to form
Common bile duct.
• Extrahepatic biliary apparatus is endodermal in origin
• Differential growth of duodenal wall pushes the opening
of common bile duct form ventral aspect to dorsomedial
aspect of duodenum along with ventral pancreatic bud.
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Anomalies of Gallbladder
• Agenesis of gallbladder
• Sessile gallbladder : Absence of cystic
duct
• Phrygian cap: Fundus is folded on itself to
form cap-like structure.
• Hartmann’s pouch: Outpouching of the
neck of the gallbladder.
• Intra-hepatic gallbladder: Gallbladder is
embedded in the substance of the liver.
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• Septate gallbladder: The lumen of the
gallbladder is divided into several segments
with partial septae.
• Double gallbladder: Two gallbladders are
present that are connected with the cystic duct.
• Floating gallbladder: Gallbladder is lined by
peritoneum on both the surfaces and is free
from the liver.
Anomalies of Gallbladder
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Anomalies of Extrahepatic Biliary Ducts
• Atresia of ducts: The ducts of the extra-
hepatic biliary apparatus may be partially
or completely absent.
• Accessory ducts: Small accessory bile
duct connecting the liver with the
gallbladder may be present.
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Development of Pancreas
• Pancreas develops from two endodermal buds:
• Dorsal bud : larger, located in dorsal mesentery
• Arises from the dorsal aspect of duodenum and
gives rise to upper part of the head, neck, body
and tail
• Ventral bud : smaller, located in ventral
mesentery Arises from the hepatic diverticulum
and gives rise to lower part of head and
uncinate process.
• Due to rotation and differential growth of walls
of duodenum the ventral bud moves to right
and comes to lie below and behind the dorsal
bud.
• Both the buds fuse in 7th wk of IUL
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• Formation of acini and islet of Langerhans:
• The proliferation of both the ventral and dorsal
pancreatic ducts form smaller ductules
• At the end of each branch, pancreatic acini appear.
Some cells of the acini get separated and form islet of
Langerhans in 3rd month and start secretion of insulin
by 5th month.
• Glucagon and Somatostatin secreting cells also
develop from parenchymal cells
• Surrounding splanchnic mesoderm condenses to
form capsule, connective tissue, septa and blood
vessels of the pancreas.
Development of Pancreas
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Formation of pancreatic ducts
• Main pancreatic duct ( Duct of Wirsung ) : 3 sources
Distal part of duct of dorsal pancreatic bud
Oblique communication between duct of dorsal and
ventral buds
Duct of ventral pancreatic bud.
Opens at major duodenal papilla.
• Accessory pancreatic duct ( Duct of Santorini ):
Proximal part of duct of dorsal pancreatic bud.
Opens at minor duodenal papilla
Development of Pancreatic duct system
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Anomalies of Pancreas
• Annular pancreas : Second part of duodenum is
surrounded by a ring of pancreatic tissue.
• Divided pancreas: Due to failure of fusion of the dorsal
and ventral pancreatic buds.
• Inversion of pancreatic duct: The main pancreatic duct is
formed by the duct of dorsal pancreatic bud and opens
at minor duodenal papilla, whereas the duct of ventral
pancreatic bud joins the common bile duct and opens at
major duodenal papilla.
• Accessory pancreatic tissue: ectopic pancreatic tissue
that lies in the wall of duodenum, gallbladder, Meckel’s
diverticulum or stomach
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Development of Spleen
• During the 5th week of IUL, mesenchymal cells in the
dorsal mesogastrium form small masses called
spleniculi or splenic lobules.
• Spleniculi fuse to form a single mass which projects to
the left and is covered by peritoneum
• The dorsal mesogastrium is divided by the developing
spleen into the ventral gastrosplenic ligament and
dorsal lienorenal ligament.
• Capsule, septa, connective tissue framework,
lymphocytes & haemotopoietic cells are all derived
from mesoderm
• Lobulated development of spleen in an adult is
indicated by splenic notches.
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• Agenesis
• Accessory spleen: Failure of fusion of spleniculi
Sites : Hilum of spleen
• Gastrosplenic ligament
• Lienorenal ligament
• Tail of pancreas
• Along the splenic artery
• Left spermatic cord
• Lobulated spleen: Incomplete fusion of
spleniculi
• Situs inversus
Anomalies of Spleen
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THANK YOU
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