Development of Gastrointestinal system & its associated developmental anomalies- PDF Lecture notes by Dr.N.Mugunthan

1. DEVELOPMENT OF
DIGESTIVE SYSTEM
Lecture By
Dr.N.Mugunthan. MBBS, MS, DNB, MNAMS, PhD,
Professor,
MGMC&RI.

2. LEARNING OBJECTIVES
Development of
 Foregut & its congenital anomalies
 Midgut & its congenital anomalies
 Hindgut & its congenital anomalies
© Dr.N.Mugunthan

3. GENERAL CONCEPT - GIT
 Formation of Primitive
Gut
 Primitive Gut- endo
dermal Yolk sac (dorsal
part)
 Ventral part –
extraembryonic yolk sac
 Connected by vitello-
intestinal duct
 Bucco-pharyngeal
membrane
 Cloacal membrane
© Dr.N.Mugunthan

4.  GIT -4 layer (inner to outer)
1. Mucosa (epithelium, lamina
propria & muscularis
interna)
2. Submucosa
3. Muscularis externa
4. Serosa
GENERAL CONCEPT – GIT CONT…
© Dr.N.Mugunthan

5. PRIMITIVE GUT TUBE
Subdivision
1. Fore gut – prelaryngeal &
postlaryngeal part
2. Mid gut – prearterial &
postarterial segment
3. Hind gut – preallontoic &
postallontaoic part
 Junction between foregut &
midgut - anterior intestinal
portal.
 Junction between midgut &
hindgut - posterior
intestinal portal.
© Dr.N.Mugunthan

6. BLOOD VESSEL OF PRIMITIVE GUT
 The midline artery-
dorsal aorta.
 Artery of fore gut-celiac
artery.
 Artery of mid gut-superior
mesenteric artery.
 Artery of hind gut-
inferior mesenteric artery
© Dr.N.Mugunthan

7. DERIVATIVES OF FORE GUT
Pre-laryngeal part
 Floor of the mouth
 Tongue
 Pharynx
 Derivatives of
pharyngeal pouches
 Thyroid
 Respiratory system
Post-laryngeal part
 Esophagus
 Stomach
 Proximal half of the
duodenum(up to the
opening of Bile duct).
 Liver, biliary apparatus
& pancreas
© Dr.N.Mugunthan

8. DEVELOPMENT OF ESOPHAGUS
 From part of the foregut
between pharynx and
stomach.
 Ventrally-laryngotracheal
groove bulges to form
tracheoesophageal septum.
 Which divides the foregut
caudal to the pharynx into
trachea and esophagus.
© Dr.N.Mugunthan

9.  Initially the esophagus is short.
Elongation is due to
1.Formation of neck.
2.Descent of diaphragm,
heart & lung.
o Lining epithelium - endoderm.
o Musculature –splanchnic
mesoderm.
Upper 1/3rd –striated muscle
only.
Middle 1/3rd - striated and
smooth muscle
Lower 1/3rd -smooth muscle only
DEVELOPMENT OF ESOPHAGUS CONT…
© Dr.N.Mugunthan

10. ESOPHAGUS – DEVELOPMENTAL ANOMALIES
 Esophageal atresia-
failure of recanalization
/ often associated with
tracheo-esophageal
fistula
 Tracheo-esophageal
fistula –different
types
 Achalasia cardia –
agenesis of nerve cells in
myenteric and
submucous plexus
© Dr.N.Mugunthan

11.  4th Week
 Stomach appears as a
fusiform dilatation distal
to the esophagus.
 Borders: ventral (lesser
curvature ) & dorsal
(grows rapidly –greater
curvature)
 Changes in Shape
 Surfaces: right & left
 Ventral Mesogastrium.
 Dorsal Mesogastrium.
DEVELOPMENT OF STOMACH CONT…
© Dr.N.Mugunthan

12. DEVELOPMENT OF STOMACH CONT…
 Changes in Position
 Rotation to right
(clockwise 90°)- around a
vertical axis
 Left surface becomes
anterior.
 Right surface becomes
posterior.
 Cephalic and caudal ends
lie in the Midline.
 As a result of this
rotation- left & right
vagus becomes anterior
and posterior vagus.
© Dr.N.Mugunthan

13. DEVELOPMENT OF STOMACH CONT…
 Rotation around its
Antero posterior axis
 Cardiac end moves to
left and downward
 Pyloric end moves to
the right and
upward
© Dr.N.Mugunthan

14. DERIVATIVES OF VENTRAL MESOGASTRIUM
Ventral mesogastrium:
Extends from the lesser
curvature to septum
transversum and anterior
abdominal wall
Derivatives:
 Falciform ligament
 Right and left triangular
ligaments.
 Superior and inferior layers
of coronary ligaments
 Lesser omentum.© Dr.N.Mugunthan

15. DERIVATIVES OF DORSAL MESOGASTRIUM
Dorsal mesogastrium:
 Extends from the greater
curvature to the posterior
abdominal wall.
Derivatives:
 Spleen.
 Gastrosplenic omentum
 Lienorenal ligament.
 Greater omentum
© Dr.N.Mugunthan

16.  Congenital hypertrophic pyloric stenosis
• Abnormal thickening of circular layer of muscularis
externa (pyloric sphincter)
• Infant prsented with distention of stomach &
projectile vomiting.
• Surgical relief of the pyloric obstruction by -
Pyloromyotomy
STOMACH – DEVELOPMENTAL ANOMALIES
© Dr.N.Mugunthan

17. DUODENUM
 2 sources
 Fore gut & midgut
 Fore gut- 1st & 2nd part
up to the opening of
ampulla of vater.
 Midgut -2nd part below
the opening of ampulla of
vater, 3rd & 4th part.
 Duodenum forms a
sagittal loop ( with ventral
convexity) attached to
posterior abdominal wall
by mesoduodenum.
© Dr.N.Mugunthan

18. DUODENUM CONT…
3 phases of development
1.Rotation
2. Fixation
3. Axial rotation (2nd part only)
1. Clockwise rotation: Sagitally
placed loop fall on the right side
 Right surface becomes posterior
(retroperitoneal) / left becomes
anterior
2. Fixation:
 Mesoduodenum is absorbed by
Zygosis and becomes retro-
peritoneal.
3. Axial rotation (2nd part
only)
 Around a vertical axis
© Dr.N.Mugunthan

19.  8th week – lumen is obliterated by proliferation of
lining endodermal cells
 3rd month end – lumen is recanalised
DUODENUM CONT…
© Dr.N.Mugunthan

20.  Duodenal atresia
a) Failure of
recanalaisation
b) Annular pancreas
 Common site –below
hepatopancreatic
ampulla
DUODENUM – DEVELOPMENTAL ANOMALIES
© Dr.N.Mugunthan

21. DEVELOPMENT OF LIVER & BILIARY APPARATUS
 4th week
 An endodermal
diverticulum – hepatic
bud
 Arises from terminal
part of foregut (ventral
border of duodenum)
 Grows into ventral
mesogastrium & reaches
septum transversum
 Hepatic bud divides into
right & left © Dr.N.Mugunthan

22.  Endodermal cell –
hepatocytes (parenchyma)
 Mesenchyme of septum
transversum – fibroareolar
stroma of liver
 Stalk of hepatic bud forms –
bile duct
 Its 2 branches forms –right
& left hepatic ducts
 Cystic bud develops from
the bile duct
 Cystic bud –becomes gall
bladder & cystic duct
 Axial rotation of 2nd part of
duodenum- bile duct open
into post.medial aspect of
2nd part of duodenum along
with ventral pancreatic
duct
DEVELOPMENT OF LIVER & BILIARY APPARATUS
CONT…
© Dr.N.Mugunthan

23. 1. Atretic gall bladder
2. Septate gall bladder
3. Double gall bladder
4. Intra hepatic gall bladder
5. Mobile or floating gall
bladder
6. Hepatocystic
communications
7. Hartmanns pouch
8. Absence of cystic duct
9. Atresia of bile duct
10. Absence of hepato-
pancreatic ampulla
BILIARY APPARATUS – DEVELOPMENTAL
ANOMALIES
© Dr.N.Mugunthan

24. DEVELOPMENT OF PANCREAS
 2 Endodermal
pancreatic buds
1. Dorsal pancreatic bud
(dorsal wall of caudal
part of foregut -dorsal
mesentry of duodenum )
2. Ventral pancreatic bud
(ventral wall of caudal
part of foregut )
 Bilobed structure, later
fused –single mass
© Dr.N.Mugunthan

25.  Rotation of duodenum
to right (C shaped )
 Ventral pancreatic bud
–Right side.
 Dorsal pancreatic bud –
Left side.
 Axial rotation of 2nd
part of duodenum-
ventral bud appears on
post.medial aspect of
2nd part of duodenum
along with bile duct
 Fusion of both buds
takes place
DEVELOPMENT OF PANCREAS CONT…
© Dr.N.Mugunthan

26. • Derivatives of dorsal
pancreatic bud - upper
part of head, neck,body
and tail
• Derivatives of ventral
pancreatic bud -
lower part of head
(uncinate process )
DEVELOPMENT OF PANCREAS CONT…
© Dr.N.Mugunthan

27. Development of
Pancreatic duct:
 Initially the ducts of
ventral & dorsal buds
open separately into the
duodenum.
 Ventral pancreatic duct
open with bile duct.
 Communication develops
between dorsal and ventral
buds.
DEVELOPMENT OF PANCREAS CONT…
© Dr.N.Mugunthan

28. Main pancreatic duct
(Wirsung)-
a.Dorsal pancreatic duct
distal to anastomosis
b.Anastomotic duct.
c.Ventral Pancreatic duct
proximal to the
anastomosis.
Accessory pancreatic
duct (Santorini)-
 Persistence of proximal
part of dorsal
pancreatic duct
DEVELOPMENT OF PANCREAS CONT…
© Dr.N.Mugunthan

29. Annular Pancreas:
 2 lobes of ventral
pancreatic bud grow and
migrate in opposite
directions around the 2nd
part of duodenum
 Forms a collar of
Pancreatic tissue before
fuses with dorsal bud
Features:
 Duodenal obstruction
 Vomiting
Treatment - duodeno-
jejunostomy
PANCREAS– DEVELOPMENTAL ANOMALIES
© Dr.N.Mugunthan

30. DERIVATIVES OF MIDGUT
 Pre-arterial segment
(Cephalic)
 Lower part of the duodenum
(caudal to the bile duct
opening)
 Jejunum
 Most of ileum.
 Post-arterial segment
(Caudal)
 Terminal part of ileum
 Caecum
 Appendix
 Ascending colon
 Right 2/3 of the transverse
colon. © Dr.N.Mugunthan

31.  Superior retention band – attachment of dorsal end of
cephalic limb (future duodeno-jejunal flexure) to body wall
by mesenchymal condensation of dorsal mesentery – persist
as suspensory muscle of duodenum or ligament of Treitz.
 Inferior retention band – attachment of dorsal end of
caudal limb (colic angle) to body wall – persist as phrenico-
colic ligament.
DERIVATIVES OF MIDGUT CONT…
© Dr.N.Mugunthan

32. DEVELOPMENT OF INTESTINES
 5th week
 Umbilical herniation
(physiological)
 Movement of
intestines into the
umbilicus
(extraembryonic part
of coelomic cavity) as it
elongates.
 Remains till 10th week
© Dr.N.Mugunthan

33. ROTATION OF MIDGUT
 First stage
(within umbilical sac)
 Anticlock wise rotation
of intestinal loop (90°)
around the axis of
sup.mesen.artery
 Cephalic limb moves
downwards and to right
and caudal limb to
upwards and left
© Dr.N.Mugunthan

34.  Second Stage(5-
10week)
 Right limb grows
rapidly and forms
jejunal & ileal loops.
 Left limb – appearance
of caecal diverticulum
(caecum and appendix).
 Re-entry of herniated
loop into abdomen
ROTATION OF MIDGUT CONT…
© Dr.N.Mugunthan

35.  Second Stage cont….
 Definitive order of reduction takes
place.
 Right limb reduces first, passing
posterior to the superior mesenteric
artery occupies the central part of
the abdomen.
 Left limb returns the last, caecum
and midgut colon appears initially in
left and then undergoes 1800
rotation to occupy the sub-hepatic
region.
ROTATION OF MIDGUT CONT…
© Dr.N.Mugunthan

36.  Second Stage cont….
 Appearance of caecal
diverticulum (6th week)
 Proximal part enlarges -
caecum
 Distal part persist as narrow
tube –appendix
 To reach the right iliac fossa-
the caecum and appendix
undergoes 2700 rotation.
ROTATION OF MIDGUT CONT…
© Dr.N.Mugunthan

37.  Third stage
 Caecum and appendix grows
caudally from subhepatic
region – right iliac fossa.
 Ascending colon – portion of
colon from right iliac fossa to
sub-hepatic region
 Fixation
 Prearterial segment of dorsal
mesentery – persist as
mesentery.
 Postarterial segment of dorsal
mesentery – persist as
transverse mesocolon.
ROTATION OF MIDGUT CONT…
© Dr.N.Mugunthan

38. Omphalocele:
 Failure of intestines return
to abdominal
 Covering of hernial sac is
the epithelium of umbilical
cord which is a derivative
of the amnion
 The size of the hernia
depends on its contents.
 Immediate surgical repair
is required
MIDGUT– DEVELOPMENTAL ANOMALIES
© Dr.N.Mugunthan

39. Anomalies of
vitellointestinal duct
1. Umbilical faecal fistula
2. Enterocystoma
3. Raspberry tumour
4. Ileal diverticulum
5. Meckel’s diverticulum
MIDGUT– DEVELOPMENTAL ANOMALIES CONT…
© Dr.N.Mugunthan

40. MECKEL’S DIVERTICULUM
 Most common anomalies of
the digestive tract.
 Occurs in 2 % of people.
 2 inch long.
 Attached to anti-mesenteric
border about 2 feet proximal
to ileo-caecal junction.
 2 times more prevalent in
males than females.
© Dr.N.Mugunthan

41.  The tip may be free or attached to umbilicus/ any
abdominal viscera by fibrous band.
 Structurally, similar to ileum.
 Occasionally, oxyntic cells secreting HCL are found
in mucous membrane and heterotopic pancreatic
tissue in muscular coat.
Complication
 Formation of peptic ulcer – perforation.
 Inflammation – peritonitis.
 Intestinal obstrucion.
MECKEL’S DIVERTICULUM CONT…
© Dr.N.Mugunthan

42. ERRORS OF ROTATION
During second stage
 Non-rotation of midgut –
umbilical ring is dilated and
permits the umbilical hernia en
masse.
 Mal-rotation (reverse rotation)
– in this caecum enters first and
rotates upward and to right behind
the superior mesenteric artery.
Transverse colon pass behind SMA
& 3rd part of duodenum lies in
front of the SMA vessel.
During third stage
 Defect in fixation – caecum and
appendix may occupysubhepatic,
right lumbar or pelvic region
© Dr.N.Mugunthan

43. DEVELOPMENT OF HIND GUT
Pre-allantoic part
 Left one third of
transverse colon
 Descending colon
 Sigmoid colon
Post-allontoic part
(endodermal cloaca)
 Rectum
 Upper part of anal canal
 Epithelium of urinary
bladder
 Most part of urethra
© Dr.N.Mugunthan

44.  The dorsal mesentery of descending colon
disappears
 The dorsal mesentery of the sigmoid colon is
retained as sigmoid mesocolon
DEVELOPMENT OF HIND GUT CONT…
© Dr.N.Mugunthan

45. DEVELOPMENT OF RECTUM & ANAL CANAL
Urorectal septum –
• A wedge of mesenchyme
divides the cloaca into
dorsal and ventral parts
• Dorsal part –
primitive rectum
(rectum and cranial
part of the anal canal)
• Ventral part –
primitive urogenital
sinus (bladder and
urethra)
© Dr.N.Mugunthan

46.  7th week -urorectal
septum fuses with cloacal
membrane
 Divide the cloacal
membrane into
urogenital membrane
(front) and anal
membrane (behind)
 Perineal body – line of
fusion of urorectal septum
&cloacal membrane
DEVELOPMENT OF RECTUM & ANAL CANAL CONT…
© Dr.N.Mugunthan

47.  Position of anal membrane represented in
adult by pectinate line
DEVELOPMENT OF RECTUM & ANAL CANAL CONT…
© Dr.N.Mugunthan

48. Rectum:
 Above the Houston’s 3rd
valve (middle rectal
valve) developed from -
Preallantoic part
 Below the Houston’s 3rd
valve developed from –
dorsal part of
endodermal cloaca
DEVELOPMENT OF RECTUM & ANAL CANAL CONT…
© Dr.N.Mugunthan

49. Anal canal:
 Above the pectinate
line – from dorsal part
of endodermal cloaca
 Below the pectinate
line – from ectodermal
proctodeum
DEVELOPMENT OF RECTUM & ANAL CANAL CONT…
© Dr.N.Mugunthan

50. DEVELOPMENTAL ANOMALIES OF HINDGUT
 Hirschsprung’s
disease (congenital
megacolon)
 Undivided cloaca
 Rectal fistula
 Recto-vesical fistula
(high fistula)
 Recto-urethral or
recto-vaginal fistula
(low fistula)
 Imperforate anus
 Ectopic anus
© Dr.N.Mugunthan

51. SUMMARY
1. Fore gut – prelaryngeal
& postlaryngeal part
2. Mid gut – prearterial &
postarterial segment
3. Hind gut – preallontoic
& postallontaoic part
Development of
 Foregut & its
congenital anomalies
 Midgut & its
congenital anomalies
 Hindgut & its
congenital anomalies
© Dr.N.Mugunthan

52. THANK YOU
© Dr.N.Mugunthan