Embryo-Digestive System

• Endoderm: epithlelium (except mouth and anal canal)
• Mesoderm: splanchnic mesoderm (smooth muscle, connective tissue, blood vessels)
• Neural Crest: autonomic ganglion (vagus)
• Ectoderm: mouth (1st arch portion) and anal canal

• Foregut
• Midgut
• Hindgut

• Pharynx and derivatives, respiratory system (6th arch)
• Esophagus, stomach, liver and pancreas, biliary apparatus, proximal duodenum (superior to yolk sac)

• Small intestine
• cecum and vermiform appendix
• ascending colon
• right half of transverse colon

• left half of transverse colon
• descending colon
• signmoid colon
• rectum
• superior anal canal
• epithelium of urinary bladder/urethra

• foregut-celiac trunk
• esophagueus to duodenum
• midgut-SMA
• Hindgut-IMA, left transverse to rectum
• SMA-axis of rotation for midgut
• viteloduct (endoderm)=same plan as SMA-another axis

• endoderm
• 6th arch
• primitive pharynx
• traneoesophageal septum-divides
• abnormalities-problems with tracheoesophagea septum -frothy saliva (bubbly) after being freed
• -esophageal atresia
• -fistula

• rotation-90 degree rotation on longitudinal axis
• -ventral border to right
• -dorsal border to left
• -left side becomes ventral
• -right side becomes dorsal
• "left hand turn 90 degrees"
• growth-posterior side=rapid

• endoderm
• parenchyma-business portion-produce liver enzyme
• -not in contact with external environment, no foreign food comes in contact here
• hepatic duct and bile duct
• all come from a single diverticulum

• endoderm
• dorsal primordia-body
• ventral primordia-near liver, head
• main duct-ventral duct
• opening in duodenum where main pancreatic duct and bile duct meet-duodenal papilla
• -rotation-as duodenum rotates to right, ventral pancreatic bud is carried dorsally
• --180 degree rotation of ventral primordia to fuse with dorsal primordia
• -abnormalities-anular pancreas (obstruction of duodenum because of rotation to the left)
• "craddle in duodenum and tickles the spleen"

• splanchnic mesoderm
• lymphnoid organ for blood sequestering platelets
• foregut

• rotation-out at 6 weeks, back at 10 weeks
• -rotates 90 degrees when it leaves, 90 degrees out in coelom, 90 degrees when it comes back=270 total
• leaves for liver-blood formation; yolk sac=3-8 wk; liver=6-30 wk; spleen=9-28 wk (helps liver), bone marrow=28 wk to adulthood
• lumen formation-definitive gut lumen
• -endoderm=proliferates into solid tube-recanalization (apotosis occurs (cell death))-hollow gut

• nonrotation-obstructions can occur; SI-right side; LI-left side
• reversed rotation-transverse colon adherent to body wall (retroperitoneal)
• duplication-food can get trapped, inflammation, infection, rupture tube
• stenosus-narrowing of GI tube, food can get trapped, severe pain, vomitin

• urorectal septum
• -cloaca (endoderm and ectoderm)-common anatomicla area where products from digestion, urinary and reproductive tracts can exit the body
• -clocal membrane (endoderm and ectoderm)
• -urorectal septum (mesoderm) grows toward the cloacal membrane and divides it
• --urogenital membrane (endoderm and ectodorm)
• --anal membrane (endoderm and ectoderm)
• ---no blood supply-degenerates openings (anus, vagina, uretra)
• anal canal
• -superior from hindgut (endoderm); superior rectal a. and v. (autonomic involuntary control-N.C.)
• -inferior from proctodeum (ectoderm)-inferior rectal a. and v. from internal pudendal a.
• -different blood an dnerve supply

• septum migrate and separate the cloaca (mesoderm)
• endoderm and ectoderm layers must meet at the right place
• anal stenosis
• covered anus-anal agenesis
• recto-urethral fistula-anus goes into urethra

• Abnormality of the vitelline duct (endoderm)-normally regresses
• Projection from ilium to abdominal wall
• can lead to intestinal obstruction, gastrointestinal bleeding, bowel spesis(rupture)

• pericardial cavity separated from pleural canals by pleuropericardial folds (mesoderm)
• lungs develop in area between pleuropericardial membrane and the pleuroperitoneal membrane
• septum transversum meets with the pleuroperitoneal membranes(mesoderm)
• below septum transversum and pleuroperitoneal membrane is the peritoneal cavity

• septum transversum (mesoderm)-doesn't migrate to post. wall
• pleuroperitoneal membrane (mesoderm)-from post. wall
• -somatic layer
• -grow toward septum transversum and fuse
• tissue from body wall pulled into the diaphragm-somites (para-axial mesoderm)

• septum tranversum (central tendon)
• pleuroperitoneal membranes (mesoderm)
• -dorsal mesentery fo esophagus (crura)-mesoderm
• -body wall (peripheral muscles)-somites

• 50%-esophageal hernias
• 36%-lef. side through posterolateral part
• -failure of pleuroperitoneal membrane and septum transversum

• mesentery: double layer of serous membrane (splanchnic)-provide way of blood vessels, n., and lymphatics to reach organs
• dorsal mesentery-entire GI tract has at some point
• ventral mesentery-only see in foregut
• visceral layer-organ
• parietal layer-on body wall; together with visceral layer make peritoneum in adult

• meso-esophagus-b/t neural tube and esophagus
• dorsal mesocardium-b/t esophagus and heart-degenerate-transverse sinus
• ventral mesocardium-b/t heart and ant. body wall-degenerates

• mesoduodenum
• mesentery proper-around S.I.=duodenum and jejunum
• mesocolon-transverse colon
• mesorectum-sigmoid colon

• dorsal mesogastrium
• ventral mesogastrium
• ventral mesentery
• greater omentum

• mesoderm
• stretches with rotation of stomach
• -splenorectal (leinorenal ligament)-b/t spleen and kidney
• -gastroleinal ligament-b/t somach and spleen
• -greater omentum-3 lig (gastrophrenic, gastrosplenal, gastrocolic)

• mesoderm
• b/t stomach and liver
• lesser omentum

• falciform ligament
• mesoderm

• due to all 3 rotations
• -omentum bursa
• -fusion of double layers (mesoderm)

• mesogastrium dorsal to spleen-pancreas fused to body wall
• mesoduodenum-2,3, 4th retro (fused to body wall)
• ascending mesocolon and descending mesocolon-mesoderm
• fixation of gut

• mesoderm
• completely suspended in mesentery-freely move
• -stomach
• -first part of duodenum
• -jejunum, ileum
• -transverse colon
• -sigmoid colon-flexible post.

• mesoderm
• fixed to body wall
• -pancreas (except tail)
• -duodenum (2-4)
• -ascending colon
• -descending colon
• -esophagus
• -rectum

• endoderm
• failure of intestine to return to abdomen between 6 and 10

• due to folding-mesoderm
• herniation of abdominal contents during week 4 due to muscular defect in abdominal wall

• peritoneal membrane failure
• herniation into thoracic cavity due to failure of the components of the diaphragm to fuse properly (mesoderm)

• mesoderm
• trapping or constriction of intestines

N.C.-fail to migrate down to that part of intestin-causes obstruction, huge colon in front

• N.C.
• enteric N.C. plexus