embrio abdomen 2

7/28/2019 Embrio Abdomen 2

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MEDICAL GROSS ANATOMY & EMBRYOLOGY

dr. Mihai Turcanu

Embryology ofGastrointestinal Tract



Contents

❖ Origin of GIT

❖

Divisions of GIT

❖ Mesenteries

❖ Foregut

❖ Midgut

❖ Hindg ut



Origin of the Gut Tube




Endoderm

❖ epitelium of GIT, glands




Endoderm


Mesoderm

❖muscle, connective tissue,peritoneum



Orig in of the Gut Tube

Endoderm


Mesoderm

❖muscle, connective tissue,peritoneum

Ectoderm

❖ buco-pharyngeal & cloacalmembrane



Divisions of the Gut Tube

❖ Embryo folding:

primitive gut

❖ endodermicportion of yolksac

❖ yolk sac

❖ allantois




Cephalic:

❖ Foregut




Cephalic:

❖ Foregut

Middle:

❖ Midgut - temporally connected to yolk sac( vitelline duct, or yolk

stalk)




Cephalic:

❖ Foregut

Middle:

❖ Midgut - temporally connected to yolk sac( vitelline duct, or yolk

stalk)

Caudal:

❖ Hindgut



Mesenteries

Dorsal and ventral mesenteries

❖ double layers of peritoneum

❖ enclose an organ

❖ connect it to the body wall



Dorsal mesentery - 5th week



Intraembryonar coelom




20th day




20th day

ectoderm




20th day

ectoderm

mesoderm




20th day

ectoderm

mesoderm

endoderm




20th day

23rd day

ectoderm

mesoderm

endoderm




20th day

23rd day

25th day




20th day

23rd day

25th day

intraembryonyc coelom




20th day

23rd day

25th day





20th day

23rd day

25th day


extraembryonyc coelom




29th day

20th day

23rd day

25th day






29th day

20th day

23rd day

25th day



CLINICAL APPLICATION



Derivates of dorsal mesentery






❖ Foregut

❖ Stomach - dorsal mesogastrium or greater omentum

❖ Duodenum - dorsal mesoduodenum






❖ Foregut



❖ Midgut

❖ jejunal and ileal loops - mesentery proper






❖ Foregut



❖ Midgut

❖ jejunal and ileal loops - mesentery proper

❖ Hindgut

❖ Colon - mesocolon

C C C O



Ventral mesentery - 5th week



Septum transversum

❖ arises from cranialmesenchyme

Forms:

❖ thoracic diaphragm

❖ ventral mesentery




Derivates of ventral mesentery





❖ Foregut

❖ Stomach & Duodenum- lesser omentum

❖ Liver - falciform ligament





❖ Foregut



❖ Midgut

❖ NOTHING





❖ Foregut



❖ Midgut

❖ NOTHING

❖ Hindgut

❖ NOTHING



Foregut5 week embryo



Foregut



Foregut❖

Esophagus❖ Trachea

❖ Lung buds

❖

Stomach

❖ Proximal duodenum ( entranceof the bile duct )

❖ Liver

❖ Pancreas

❖ Biliary apparatus

❖ Celiac trunk



4th week

Esophagus



4th week

Esophagus

❖ respiratory

primordium andesophagus

❖Respiratorydiverticulum ( lung

bud )

❖Tracheoesophagealseptum



Lung bud




Esophageal Abnormalities

❖ Esophageal atresia(polyhydramnios )

❖ Esophageal stenosis

❖ Tracheo-esophageal fistula




Stomach



❖ 4th week: fusiformdilatation

Stomach




❖ 90° rotationclockwise ( vagusnerve )

Stomach



Stomach



Stomach Abnormalities





❖ Pyloric stenosis

❖

Hypertrophy of circularmusculature

❖ Most common






❖


❖ Most common

❖ Atretic pylorus






❖


❖ Most common

❖ Atretic pylorus

❖ Prepyloric septum



❖Duodenum and head of the pancreas - fixed in a retroperitonealposition ( dorsal mesoduodenum disappears )

Duodenum



Liver



Liver

❖ 10th week:

❖ 10 % of the total body weight

❖ hematopoietic function

❖ 12th week:

❖

bile is formed

❖ bile can enter the gastrointestinal tract ( dark green )




Liver and Gallbladder Abnormalities

❖Variations in liver lobulation

❖ Accessory hepatic ducts

❖ Intrahepatic biliary duct atresia and hypoplasia

❖Duplication of the gallbladder

❖ Failure of recanalization ( extrahepatic biliary atresia )

❖










❖




Pancreas



Pancreas

a.dorsal and ventralpancreatic buds



Pancreas


b.ventral bud rotates behindthe duodenum



Pancreas


b.ventral bud rotates behindthe duodenum

c.rotation involves superiormesenteric artery

d.formation of uncinateprocess



Pancreas

❖

3rd

month:❖ pancreatic islets ( Langerhans )

❖ 5th month:

❖

Insulin secretion




Pancreatic Abnormalities




❖ In about 10% of cases the duct system fails to fuse, and the

original double system persists❖Accessory pancreatic tissue

❖Annular pancreas:

❖ The right portion of the ventral bud migrates along its normal route, butthe left migrates in the opposite direction

❖ Complete obstruction of duodenum





Foregut



Midgut

❖ Primary intestinal loop

❖ Distal duodenum

❖

Jejunum

❖ Ileum

❖ Ascending colon

❖ Right two-thirds of thetransverse colon

❖ Superior mesenteric artery



Midgut❖ rapid elongation of the gut and its mesentery



Midgut

❖ cephalic limb

❖ caudal limb




❖ 6th week:

❖ Rapid elongation of the cephaliclimb

❖ Rapid growth of the liver

❖ Intestinal loops enter theextraembryonic cumbilical cord

Physiological herniation



❖ Axis: superior mesenteric artery

❖Counterclockwise

❖ Approximately 270°

❖ during herniation ( about 90° )

❖ during return ( remaining 180° )

Rotation of Midgut



Rotation of Midgut



Rotation of Midgut - great omentum



Great omentum



❖

10th

week:❖ loops begin to return to the abdominal cavity

❖ regression of the mesonephric kidney, reduced growth of theliver, expansion of the abdominal cavity

❖ Jejunum – left

❖ Loops – more to the right

Retraction of herniated loops



Retraction of herniated loops




Body Wall Defects

❖Omphalocele

❖ Herniation through enlargedumbilical ring

❖ 6th to 10th weeks

❖ associated with a high rate of mortality ( 25%) and severe

malformations

❖ associated with chromosomeabnormalities




Body Wall Defects

❖Gastroschisis

❖ herniation through the body wall - lateral right

❖ not associated withchromosome abnormalities

❖ Cocaine

❖ Volvulus




Vitelline Duct Abnormalities

❖ Portion of the vitelline duct persists




Gut Atresia and Stenosis❖ Most occur in the duodenum ( lack of recanalization )

❖ vascular "accidents“



Midgut



Hindgut

❖Distal third of thetransverse colon

❖Descending colon

❖ Sigmoid colon

❖Rectum

❖Upper part of the analcanal

❖ Inferior mesenteric artery



Hindgut



Hindgut

❖ Primitive anorectal canal

❖

7th

week: cloacal membrane ruptures

❖ Tip of the urorectal septum: perineal body



Hindgut❖ Primitive anorectal canal

❖ 7th week: cloacal membrane ruptures

❖ Tip of the urorectal septum: perineal body




Hindgut Abnormalities

❖ Rectoanal atresias, and

fistulas

❖ Imperforate anus

❖ Congenital megacolon( aganglionic megacolon:

Hirschsprung disease )



Hindgut



“Fagaras” Mountain, Carpathians, Romania

embrio abdomen 2

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