-endoderm from original yolk sac

-will form epithelial lining of digestive tract and the structures derived from it

-initially suspends the foregut, midgut and hindgut

-begins at caudal extend of esophagus, continues to hindgut

-less extensive

-derived from septum transversum

-anchors lower end of esophagus, stomach, and 1st part of duodenum to the anterior body wall

-originates from the foregut immediately posterior to the pharynx

-at 4 weeks, the lung buds evaginate from the ventral surface of the forming esophagus

-it is then separated from the forgut by the tracheoesophageal septum

-by 8 weeks, endodermal epithelal cells proliferate and obliterate lumen of esophagus

-recanilization of this segment is accompanied by changes in its epithelial lining

-tracheoesophageal fistula or esophageal atresia: defect in formation of tracheoesophageal septum

-if recanilization fails to occur, esophageal atresia or stenosis occurs: prevents embryo from swallowing normal amount of amniotic fluid, resulting in polyhydramnios (excess fluid in amniotic sac)

- develops as spindle shaped enlargement of the forgut during the 4th week --> originally lies in median plan but due to differnetial growth patterns and rotation, its position and overall shape undergo dramatic changes

-rotation results in pulling the dorsal mesentery to the left

-as it grows, the mesentery balllons out to form the lesser sac, etc.

- develops from the ballooning out of the dorsal mesentery

-defined space behind the stomach

-forms from the growth of the dorsal mesentery and the omental bursa

-bi-layered pouch attached to greater curvature of the stomach

-eventually the posterior layer fuses w/ the mesentery of the transverse colon to form the transverse mesocolon and the space in the "pouch" of the greater omentum is obliterated

-formed from the ventral mesentery associated w/ the stomach

-runs b/w liver and stomach and 1st part of duodenum

-in adult it is subdivided into hepatogastric and hepatoduodenal ligaments

-forms from the ventral mesentery associated w/ the stomach

-develops from caugal foregut and cranial portion of the midgut as C-shaped, ventrally positioned loop

-rotates to the right w/ movement of the stomach

-due to repositioning during growth, the mesoduodenum fuses w/ the peritoneum covering the posterior body wall --> except for cap, duodenum is secondarily fixed

-recanilization usually complete by 8th week (epithelial cells of lining differentiate)

-Duodenal stenosis (narrowing of lumen) or duodenal atresis (complete occlusion lumen) can occur if canalization is incomplete or absent

-infants with this defect initially exhibit polyhydramnios (begin vomiting shortly after birth)

-endodermal cells from ventral surface of caudal foregut

-differentiate into liver bud and become invested in the ventral mesentery (from septum transversum)

-the ventral mesentery that cover the surface becomes visceral peritoneum

-primary hematopoetic organ, produces both RBC and WBC's as early as 6 weeks

- at cranial aspect, liver is in direct contact w/ mesodermal cells that will become the central tendon of the diaphragm

-no peritoneal covering between liver and inferior diaphragm surface

-endodermal outgrowth from ventral surface of caudal foregut

-cystic diverticulum first appears as small outpouching from proximal portion of hepatic diverticulum (liver bud)

-attached to hepatic duct via cystic duct (forms common bile duct)

-initially on ventral surface duodenum, after rotation the definitive common bile duct is on the dorsal aspect of this organ

-endodermal outgrowth from ventral surface of the caudal foregut

-due to rotation of the duodenum, ventral pancreatic bud is carried posteriorly and fuses w/ the larger dorsal bud to form the head and uncinate process

- endodermal outgrowths from the ventral surface of the caudal foregut

- arises from dorsal pancreatic bud which fuses with the smaller ventral bud

- originates from the ventral pancreatic bud

-maintains original association with bile duct to form hepatopancreatic ampulla

- formed from presence and subsequient fusion fo a portion of an anomalous double (bifid) ventral pancreatic bud w/ the dorsal pancreatic bud

- a ring of pancreatic tissue that surrounds the duodenum, constricting and obstructing it

-mesoderman origin

-hematopoetic organ

-during 5th week it develops w/in dorsal mesentery

-due to rotation of stomach, left surface of mesentery fuses w/ peritoneum covering the developing left kidney

-in adult, spleen retains intraperitoneal location --> connected to body wall via splenorenal ligament

-for about 5 weeks, the intestinal tract develops outside of the body, protruding into the umbilical cord

-the cranial limb component of the primary intestinal loop grows into the distal part of the duodenum, jejunum, and part of the ileum

- elongating large intestine roates 90 degrees around the SMA (on the left)

-during 10th week intestines are restored to abdominal cavity, w/ small intestine returning first

-the caudal limb of the primary intestinal loop will develop into the cecum and appendix (from the caecal diverticulum)

- elongating large intestine roates 90 degrees around the SMA (on the left)

-during 10th week intestines restored to abdominal cavity, large intestine returns 2nd and undergoes 180 degree rotation, the cecum descends to lower right quadrant

-Nonrotation, reversed rotation, mixed rotation or malrotation: all involve disparate movements of small intestine that result in abnormal positioning of GI tract and associated mesenteries (most not life threatening)

-volvulus: propensity for gut to twist upon itself, portion of small bowel may become obstructed and the vascualr supply severely compromised

-persistence of vitelline duct as a blind pouch, usually projects from distal ileum

-intestinal obstruction and gastrointestinal bleeding are potential complications

-occasionally a ligament may connect a meckel's diverticulum to the umbilicus

development of hindgut

(1/2 transverse colon, descending and sigmoid colon, rectum, superior anal canal, epithelium urinary bladder and urethra)

- endoderm of hingut ends at cloaca, which is sealed by the cloacal membrane and then lined internally by endoderm and covered externally by ectoderm of anal pit

-6th week: urorectal septum separates cloaca into anterior urogenital sinus and posterior rectum and anal canal

-superior 2/3 anorectal canal forms from endoderm hingut, inferior 1/3 originates from ectoderm of anal pit

-junction b/w two regions marked by pectinate line (different vessels and nerves supply the anorectal canal on either side of it)

-# of defects that relate to absence of an anal opening

-congenital persistence of anal membrane is amenable to straightforward surgical procedures

-atresia of anal canal/rectum is more difficult