Development of digestive tract

8/7/2019 Development of digestive tract

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Dr. Leandro D. Villa, M.D.


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Digestive systemy Endoderm and mesoderm

y Beging of 4th week

y Primitive gut closey 3 part of primitive gut:

1. foregud

2.Midgut

3.hindgut

Closed by oropharyngeal membrane at cranial end

Closed by cloacal membrane at caudal end


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y The derivatives of the foregut are :

y The primordial pharynx and its derivatives

y The lower respiratory systemy The esophagus and stomach

y The duodenum, distal to the opening of the bile duct

y The liver, biliary apparatus (hepatic ducts, gallbladder,

and bile duct), and pancreas


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Foregut

y 1. pharynxy 2. esophagusimmediately caudal to the pharynx

-7th week-final length

Its epithelium and glands are derived from endoderm.The striated muscle forming the muscularis externa of the superior

third of the esophagus is derived from mesenchyme in thecaudal pharyngeal arches.

The smooth muscle, mainly in the inferior third of the esophagus,develops from the surrounding splanchnic mesenchyme

y 3. stomach-Fusiform dilatation at the caudal foregut (4th week)-90 rotation clockwise( longitudinal axis)-Omental bursa


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y 4 . Dodenum

-From foregut and hindgut

-C-shaped loop as stomach rotates-2nd month lumen is obliterated

-(5th 6th week)

y 5. hepatobilary tract

-3rd week-5 th -10th- rapid growth

-week 6th week-hematopoiesis

-9th week- 10 percent of fetal weight


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-12th week-bile formation

-13th week-bile enter the doudenum

-Outgrowth of endodermal epithelium from distalforegut (hepatic diverticulum)

-Septum transversum

-Bile duct

-Gall bladder and cystic duct

-Kupffer cells, hepatopoietic cells, CT cells


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y 6. pancreas-from

A. dorsal pancreatic bud

-most portions of pancreasB. ventral pancreatic bud

-inferior head of pancreas-uncinate process

-duct of wirsung -----major pancreatic ductand duct of santorini ------accessory pancreatic ductIslets of langerhans (3rd month)Insulin (5th month)


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midguty The derivatives of the midgut arey The small intestine, including the duodenum distal to the

opening of the bile duct

y The cecum, appendix, ascending colon, and the right onehalf to two thirds of the transverse colon

-6th week physiologic hernation-10th week reduction of hernation due to the enlargement

of the abdominal cavity, and the relative decrease in thesize of the liver and kidneys are important factors.

-90 rotation counterclockwise rotation then 180


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y The primordium of the cecum and wormlike (Latin,vermiform) appendix-the cecal swelling

(diverticulum)-appears in the sixth week as anelevation on the antimesenteric border of the caudallimb of the midgut loop


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Hindguty Distal tranvese colon to upper anal canal

y Cloaca

-recives allantois ventrally-Urorectal septum (ventral/dorsal)

A. rectum and anal canal dorsally

B. Urogenital sinus ventrally

-fusion on perineal body

-7th week- fusion of septum and cloacal membrane


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y -septum divides the cloacal membrane to:

y A. posterior- external anal sphincter

y B. anterior bulbospongiosusischiocavernosus

ALL SUPPLIED BY PUDENDALNERVE

Proctodeum (rectum and anus)

End of 8th week anal membrane ruptures

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Development of digestive tract