dr.anggraini - development of gastrointestinal system

7/28/2019 Dr.anggraini - Development of Gastrointestinal System

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Development of

Gastrointestinal SystemDr Anggraini Barlian


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DEVELOPMENT OF GASTROINTESTINAL SYSTEM

Derivatives of endoderm only epitheliallayer of gastrointestinal tract and glands

The first tube, extending throughout thelength of the body is: the digestive tube

Buds from this tube form: the liver,gallbladder and pancreas


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The digestive tube is derived from the primitive gut. Asthe endoderm pinches in toward the center of theembryoforegut and hindgut regions are formed.


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The endodermal covers the ventral surface of the embryo &

forms the roof of the yolk sac

In the anterior, endoderm forms : foregut

In the tail region, endoderm forms: hindgut. Between: midgut

Midgut yolk sac by broad stalk: vitelline duct

At cephalic end, foregut bounded temporarily by ectodermal-

endodermal membrane: buccopharyngeal membrane

4th

week ruptures: open connection amniotic cav. & primitive gut

oral cavity

Hindgut 7th week breaks down : create openings: cloacal

membrane

In human yolk sacvestigial : has nutritive role in early


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At 16 days,

primitivegutappears

still opens,until theposteriorbody fold

begins,then formshindgutandmidgut


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Human embryo at 18 days: 3 parts of digestive

tube: foregut, midgut and hindgut


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At first, the oral endis blocked by aregion of ectodermcalled the oral plateor stomodeum.

Eventually, at 22days thestomodeum breaks creating the oral

opening of thedigestive tube. Theopening itself islined by ectodermal

cells.


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At 28 days, budsfrom the digestivetube formimportantdigestive glands:

Liver Pancreas

Gallbladder

Digestive tubefurther

differentiates


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The digestive tube and its derivatives

Posterior of the pharynx, the digestive tubeconstricts to form the esophagus which isfollowed by the stomach, small intestine andlarge intestine

The endodermal cells generate only the lining of

the digestive tube and its glands

Mesodermal mesenchymal cells will surroundthis tube to provide the muscles for peristalsis


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Specification of gut tissue

Endodermal epithelium responds differentlyto different regionally specific mesodermal

mesenchymes different structure at

different regions (Sonic hedgehog or Shh gene

action):

- esophagus

- Stomach- Small intestine

- colon


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Further development

of digestive tube:

Esophagus

Pharyngeal arches:

tongue bud


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Sagittal section of 3 weeks human

embryo: the stomach region has

begun to dilate, the pancreas isrepresented by 2 buds that will fuse


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LIVER

Develop caudal to stomach; from liver/ hepaticdiverticulum. Developing of heart induces liverformation

The hepatic diverticulum is the tube of endoderm thatextends out from the foregut into the surroundingmesenchyme (cardiogenic mesoderm)

The mesenchyme induces this endoderm to proliferate,to branch and to form the glandular epithelium of theliver


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Liver development.

A portion of the hepatic diverticulum (closest

to digestive tube) continues to function as the

drainage duct of the liver and branch from this

duct produces: gallbladder


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PANCREAS

Develops from the fusion of distinct dorsal andventral diverticula

Both dorsal and ventral diverticula arise from thendoderm immediately caudal to the stomachgrow, come closer togetherfuse

Only the ventral duct survives to carry digestiveenzymes into the intestine. Once pancreaticrudiments are initiated, they begin to form bothexocrine and endocrine tissue.


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Pancreatic development in human:A. At 30 days, ventral pancreatic bud is close to the liver

primordiumB. By 35 days it begins migrating posteriorlyC. Comes into contact with the dorsal pancreatic bud

during the 6th week of developmentD. Dorsal pancreatic duct loses its duct into the

duodenum. In about 10% of population the dual duct

system persist

dr.anggraini - development of gastrointestinal system

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