Embryonic Development of the Gastrointestinal Tract PDF

(004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21...

(004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 OUTLINE I. DIVISION OF GUT TUBES II. PRIMITIVE GUT: FROM DORSAL PART OF YOLK SAC III. GENERALITIES IV. MOLECULAR REGULATION V. TRANSCRIPTION FACTOR (TF) VI. MESENTERY A. Dorsal Mesentery B. Ventral Mesentery VII. PRIMITIVE GUT VIII. FOREGUT DERIVATIVES A. Esophagus B. Stomach C. Vagus Nerve D. Arteries E. Greater Omentum F. Duodenum Figure 2. Diagrams showing molecular regulation of gut G. Liver development. (A) Diagram indicating genes responsible for H. Bile Duct initiating regional specification. I. Gallbladder J. Pancreas K. Midgut L. Esophagus IX. INNERVATION OF THE GUT TUBE X. DEVELOPMENT OF HINDGUT XI. CLINICAL CORRELATIONS I. DIVISION OF GUT TUBE Figure 3. Sagittal sections through embryos at various stages of developent. (A) Presomite embryo (B) Embryo with seven somites (C) Embryo with 14 somites (D) At the end of the first month. Figure 1. Cephalocaudal - Lateral folding. II. PRIMITIVE GUT: FROM DORSAL PART OF Cephalocaudal and Lateral Folding : Endoderm Incorporation = THE YOLK SAC primitive gut forms blind ending tubes Foregut and Hindgut Foregut Pharyngeal gut/pharynx – from oropharyngeal Hindgut membrane to respi diverticulum (Head and Neck) Midgut Foregut- extends up to the liver. Midgut remains temporally connected to yolk sac by vitteline duct. Midgut- after liver up to junction of left 3rd of transverse colon. Hind gut- from the left 3rd of Transverse colon to cloacal membrane. Page 1 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 III. GENERALITIES V. TRANSCRIPTION FACTOR (TF) The epithelium of and the parenchyma of glands SHH secreted from the endoderm for epithelial associated with the digestive tract (e.g., liver and mesenchymal interaction -determines the specific gut pancreas) are derived from endoderm. structure. Gland stroma: from visceral/splanchnic mesoderm HOX genes influence cephalic-caudal regions of the gut The muscular walls of the digestive tract (lamina propria, tube -formation of component of mid and hind gut. muscularis mucosae, submucosa, muscularis externa, adventitia and/or serosa) are derived from splanchnic VI. MESENTERY mesoderm. During the solid stage of development, the endoderm of Portion of the gut tube and its derivatives are suspended from the the gut tube proliferates until the gut is a solid tube. There dorsal and ventral body wall by mesenteries. will be a time that the small intestines will have no canal Primitive gut is connected to posterior abdominal wall at all and later they will recanalize. mesenchyme and narrows by 5th week However, a process of recanalization restores the lumen. Dorsal mesentery (from fusion of mesodermal layers) takes over from esophagus to rectum IV. MOLECULAR REGULATION double layer membrane nerve, BV and Lymphatic Pathway Regional specification of the gut tube into different components Intraperitoneal- are organs that are enclosed by double layer of occurs during the time the lateral body folds are bringing two sides peritoneum. of tube together. Retroperitoneal- organs that lie against the posterior body wall Retinoic Acid concentration gradient initiate regional specification. and covered by peritoneum on their anterior surface only such as Pharynx is exposed to low or even no RA vs Colon exposed to the kidney. high concentration of RA. Primitive dorsal and ventral mesenteries Causes Transcription Factor (TF) expression in the gut 1. SOX2 – esophagus and stomach development A. DORSAL MESENTERY 2. PDX1- duodenum Dorsal mesogastrium (in the stomach) 3. CDXC – small intestine Or Greater omentum 4. CDXA – large colon Mesoduodenum (in the deudenum) Endodermal cells secrete SHH protein Mesentery Mesoderm the express HOX gene Mesocolon (Colon) HOX Genes depending on the area like example HOX 9-10 for Mesoappendix small intestine development, HOX 9-11 for cecum development, Mesentery proper (Jejunal and ileal loops) HOX 9-12 for large intestine development, and HOX 9-13 for Mesosigmoid cloacal development Mesorectum B. VENTRAL MESENTERY From septum transversum Growth of the liver into the mesenchyme of the septum transversum will divide into lesser omentum and falciform ligament. o Ventral mesogastrium (lesser omentum) – attachment for lesser omentum and falciform ligament. The lesser omentum will be the attachment of of the stomach as well as the proximal duodenum to the liver Figure 4. Transverse sections through embryos at various stages o Falciform ligament – attachment of the liver to of development (A) The embronic cavity, (B) The intraembryonic the body wall cavity is losing its connection with the extraembryonic cavity (C) At Continuous with dorsal mesentery the end of the fourth week. Visceral VS. Parietal peritoneum Page 2 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 Peritoneal reflection – junction between organ and inner Lower 1/3 smooth (muscle coat is smooth): splanchnic posterior abdominal wall plexus. One consequence of the tail folding is the incorporation of Initially short but lengthens rapidly as the heart and lungs the allantois descend. Allantois forms the cloaca 4 weeks old embryo, respiratory diverticulum (lung bud) Distal allantois remains in connecting stalk appears at the ventral wall of the foregut at the border of the pharyngeal gut, which will be gradually partitioned by By Day 35 the connecting stalk and the yolk sac stalk will fuse to tracheoesophageal septum from the dorsal part. form the umbilical cord Foregut divides into ventral (respiratory primordium) and dorsal (esophagus) Figure 6. Development of Esophagus and Trachea. Figure 5. Primitive dorsal and ventral mesenteries. VII. PRIMITIVE GUT Stomodeum – ectoderm at cranial end of the gut Foregut – endoderm and splanchnic mesoderm Midgut – endoderm and splanchnic mesoderm Hindgut – endoderm and splanchnic mesoderm Proctodeum – anal pit – ectoderm at caudal end of GI tract VIII. FOREGUT DERIVATIVES Figure 7. Embryos during the fourth (A) and (B) fifth weeks of Pharynx (with derivatives tonsils, tongue, salivary development showing formation of gastrointestinal tract and the glands, etc) various derivatives originating from the endodermal germ layer. Lower respiratory system Esophagus Stomach Duodenum (proximal to bile duct) Liver, biliary system and pancreas A. ESOPHAGUS The cephalic foregut is partitioned by the tracheoesophageal septum (4wks onwards). Initially short but lengthens as heart and lungs descends. Figure 8. Succesive stages in development of the respiratory Upper 2/3 striated (muscular coat by surrounding visceral diverticulum and esophagus through partitioning of the foregut (A) mesenchyme): Vagus at the end of the third week (lateral view) (B,C) during the fourth week (ventral view). Page 3 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 o Dorsal wall of stomach grows faster than the ventral wall giving rise to greater and lesser curvature. As the stomach grows: o The ventral surface rotates to the right. o The dorsal border moves to the left. o The left side becomes the ventral surface. o The right side becomes the dorsal surface. Cranial region moves inferiorly and the left. Caudal region moves superiorly and to the right. Long axis of stomach becomes nearly transverse. Figure 9. Variation of esophageal atresia and/or tracheoesophageal fistula on order of their frequency of appearance (A) 90% (B) 4% (C) 1% and (E) 1%. B. STOMACH Figure 11. (From left to right) Showing the rotation of stomach. Figure 10. Formation of stomach. During the 4th week caudal foregut begins to dilate Initially oriented in the median plane Begins development from the foregut in the 4th week as fusiform dilation Growth to lengthen the esophageal region is essential for positioning of the stomach in the abdominal cavity Diaphragmatic hernia results if stomach remains in the thoracic cavity and compressing the lungs Positional change is assumed to rotate around a longitudinal and an anteroposterior axis (90°) causing Figure 12. (A-C) Rotation of the stomach along its longitudinal axis as seen anteriorly (D,E) Rotation of the stomach around the right side to face posteriorly anteroposterior axis. Note the change in position of the pylorius Initially, vagus nerve innervates the left, but due to and cardia. positional changes, it now innervate the anterior side while the right VN innervates the posterior Original posterior wall of the stomach grows faster than C. VAGUS NERVE the posterior, forming the greater and lesser curvatures The rotation of the stomach leaves the: Originally, cephalic and caudal ends lie in the midline o Left vagus During further development, stomach rotates o s nerve on the ventral surface of the stomach (caudal/pyloric part moves right and upward; (Anterior Vagal Trunk). cephalic/cardiac part moves left and slightly downward o Right vagus nerve on the dorsal surface of the Dorsal Mesogastrium-dorsal body wall attachment stomach (Posterior Vagal Trunk) Ventral Mesogastrium-ventral attachment, part of septum transversum D. ARTERIES During the next two weeks: Since the foregut distal to the esophagus is supplied by the celiac artery, branches of this artery supply the stomach. Attachment: Page 4 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 Dorsal mesogastrium Ventral mesogastrium This happens in the 4th week wherein the intracellular cleft on the mesogastrium Ventral Mesentery-from ventral mesogastrium which becomes thinner o Lesser omentum – liver attachment of stomach ▪ Portal pedicle - connection to duodenum Free margin is thickened forming the PORTAL TRIAD (Bile duct, portal vein, hepatic a.) Figure 14. (A) The positions of the spleen, stomach, and pancreas Forms roofs of epiploic at the end of the fifth week. (B) Position of spleen and stomach at foramen (of Winslow) the 11th week. o Falciform ligament - liver connection of ventral body wall ▪ Free margin contains umbilical vein E. GREATER OMENTUM (obliterated at birth forming the round From downward growth of dorsal mesogastrium. Initially ligament of the liver-Ligamentum as two layers and fuse teres hepatis) Double layered apron formed from the growth of the Omental bursa/lesser peritoneal sac space behind the dorsal mesogastrium stomach due to rotation. Omental Bursa (Lesser Posterior layer fuses with mesentery of the GI tract. Peritoneal Sac- a space created from the rotation pulling the dorsal mesogastrium to the left Lesser omentum pulled to right Spleen from mesoderm proliferate in dorsal mesogastrium. o Lienorenal reflection of peritoneum (left kidney) o Gastrolienal reflection (stomach) Figure 15. (A) Sagittal section sowing the relation of the greater omentum, stomach, transverse colon and small intestinal loops at 4 months (B) Similar sections but in a newborn. Figure 13. Transverse section through a 4-week embryo showing intercellular clefts appearing in the dorsal mesogastrium (B,C) The clefts have fused, and the omental bursa is formed as an extension of the right side of the intraembryonic cavity behind the stomach. Figure 16. Transeverse sections through the region of the stomach, liver, and spleen. Page 5 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 Figure 17. Transverse sections through the region of the Figure 18. Upper portion of the Duodenum showing the solid duodenum at various stages of development. stage (A) and cavity formation (B) produced by recanalization. 1) Pyloric Stenosis - Hypertrophy of circular and or longitudinal muscle in pylorus G. LIVER - 3-5 after birth 1) DEVELOPMENT OF THE LIVER - Erythromycin a. Liver bud also known as hepatic diverticulum. - Projectile vomiting b. Endodermal cells grow toward septum transversum (by the middle of the 3rd week) F. DUODENUM c. Endodermal cords mix with cells of vitelline Derived from: foregut (terminal part) up to the bile duct veins to form liver parenchyma. (first and second parts). d. Hemopoietic cells, Kupffer cells and connective Cephalic midgut from bile duct to jejunum tissue from mesoderm of septum transversum Junction of the 2 parts is directly distal to the origin of e. FGF2 from cardiac mesoderm and vascular the liver bud endothelial cells Supplied by celiac artery and superior mesenteric artery f. Bone morphogenetic proteins branche g. Both aids in liver and biliary cell linage differentiation 1) GROWTH OF THE DUODENUM h. Regulated by hepatocyte nuclear transcription i. Grows as a C-shaped loop that projects factor 3 and 4. ventrally as the stomach rotates (together with 2) LIVER FUNCTION the head of the pancreas, swings the a. Early function is hemopoiesis (blood duodenum from its initial midline position to the production) right side of the abdominal cavity) b. Activity diminishes during the last 2 months of ii. Most of the duodenum will be attached to the gestation posterior body wall except for the duodenal cap c. At 7th month, the role of liver to blood (retains as an extension of mesentery) production ends. Changes are shifted into the 2) ROTATION OF THE DUODENUM bone marrow. i. As the stomach rotates so does the duodenum. ii. As the duodenum loop rotates, it rotates to the H. BILE DUCT right. As the liver develops, the epithelium between the liver and iii. Eventually comes to lie in a retroperitoneal the foregut narrows and forms the bile duct. position 3) DUODENAL DEVELOPMENT i. During the 5th and 6th weeks I. GALL BLADDER ii. The duodenal lumen becomes plugged by A diverticulum develops from the bile duct giving rise to the epithelial cells Later recanalized (If no gall bladder and the cystic duct. recanalization happens, there will be an Bile duct becomes solid, then the lumen opens again. atresia) Epithelial liver cords intermingle with the vitelline and iii. 2nd month-lumen is obliterated by proliferation umbilical vein forming hepatic sinusoids. of cells in its walls. Page 6 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 o  (pancreatic polypeptide) cells -PAX 6 only: o (glucagon) cells Glucagon and somatostatin-secreting cells also develop from parenchymal cells. Visceral mesoderm surrounding the pancreatic buds forms the pancreatic connective tissue. Insulin secretion begins at 5 months of gestation. Figure 19. (A) Obliteration of the bile duct resulting in distention of the gallbladder and the hepatic ducts distal to the obliteration. 1) MOLECULAR REGULATION OF PANCREAS (B) Duplication of the gallbladdder. DEVELOPMENT J. PANCREAS a. FGF2 and ACTIVIN (a TGF-B family member) Originates from two pancreatic buds: b. Secreted by the notochord. Dorsal pancreatic bud in dorsal mesentery c. Repress SHH in endoderm to become pancreas. Ventral pancreatic bud is near the bile duct. d. As a result, Pancreatic and Duodenal hemeobox 1 (PDX) gene upregulated. During rotation of the duodenum the ventral bud moves dorsally. e. Expression of the paired homeobox genes PAX4 Ventral bud will lie caudal and posterior to the dorsal bud. and PAX6 specifies the endocrine cell lineage, such that cells expressing both genes become Ventral bud forms uncinate process and inferior insulin, somatostatin, and pancreatic polypeptide pancreatic head. cells; whereas those expressing only PAX6 Dorsal bud makes up rest of gland become a (glucagon) cells. Main pancreatic duct is formed from dorsal and ventral pancreatic duct. The proximal part of the dorsal pancreatic duct either is K. MIDGUT obliterated or persists as a small channel, the accessory In the 5-week embryo, the midgut is suspended from the pancreatic duct (of Santorini). dorsal abdominal wall by a short mesentery and The main pancreatic duct, together with the bile duct, communicates with the yolk sac by way of the vitelline enters the duodenum at the site of the major papilla; the duct or yolk stalk. entrance of the accessory duct (when present) is at the In the adult, the midgut begins immediately distal to the site of the minor papilla. entrance of the bile duct into the duodenum and terminates at the junction of the proximal two-thirds of the transverse colon with the distal third. Supplied by the superior mesenteric artery. During early development there is a rapid growth of both the midgut and its mesentery. Cephalic and Caudal limbs of the midgut Figure 20. Stages in development of pancreas (A) 30 days - approx. 5mm (B) 35 days - approx. 7mm. Islet of Langerhans develop from parenchymatous tissue during the 3rd month of gestation. Figure 21. Development of Midgut. o They scatter throughout the pancreas. Midgut forms a primary intestinal loop -PAX 4 and PAX 6 specify cells to become: Loop remains in connection with yolk sac. o  (insulin) cells Connection is called the vitelline duct o  (somatostatin) cells If vitelline duct persists it is called a Meckel’s diverticulum. Page 7 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 X. DEVELOPMENT OF THE HINDGUT 1) PHYSIOLOGICAL UMBILICAL HERNIATION 6th week abdominal cavity cannot contain the a. Terminal portion of in contact with the ectoderm via gut. cloacal plate or cloacal membrane b. Midgut migrates into the umbilical cord. Membrane is endoderm of hindgut and ectoderm of anal 2) RETURN TO THE MIDGUT pit. a. Midgut returns at 10-12 weeks Cloaca is expanded portion of hindgut b. Reason: Cloaca receives the allantois (sac filled fluid with c. Regression of mesonephric kidney embryonic and extra embryonic tissues which play a role d. Reduced growth of the liver. for gas exchange and waste) e. Increased size of the abdominal cavity f. First to return is the jejunum- on the left side HINDGUT g. As the other parts return, they are located to Distal 3rd of TC, DC, simoid, rectum and upper anal canal. the right. endoderm of the hindgut also forms the internal lining of the h. Cecum is the last part to return. bladder and urethra i. Located on the right side under the liver. Terminal hindgut enter urogenital sinus. j. From there it is descends and forms the Allontois enter urogenital sinus. ascending colon and hepatic flexure. Distal end Urorectal septum (Mesoderm separating allantois and of cecal bud forms appendix. hindgut) comes in contact with cloacal membrane. 3) ROTATION OF THE MIDGUT Cloacal membrane is the boundary between ectoderm and a. The Midgut rotates around the superior endoderm. mesenteric artery. Cloacal membrane ruptures at 7th week = anal opening and b. This rotation is counterclockwise rest degenerate for continuity of canal. c. Even during rotation, elongation of the small Lower third is ectoderm derived (protodeum), proliferate intestinal loop continues, and the jejunum and and invaginate= anal pit. ileum form a number of coiled loops. Junction between ectoderm and endoderm = pectinate d. The large intestine likewise lengthens line, epithelium changes. (from columnar to stratified considerably but does not participate in the squamous epithelium) coiling phenomenon. e. Rotation occurs during herniation. XI. CLINICAL CORRELATIONS f. 90 degrees during herniation 1) MESENTERY DEFECTS a. Volvulus Of The Cecum And Colon g. 90 degrees during herniation i. ascending portion of the colon fails to h. 180 degrees during the return i. Return of the intestinal loops into the attach to the posterior abdominal abdominal cavity wall,a mobile colon results, which may i. A total of 270 degrees allow it to twist upon. b. Retrocolic Hernia i. formed when entrapment of portions of the small intestine posterior to the ascending portion of the colon occurs. Figure 22. (From left to right) Rotation of midgut week 6, 8 and 2) BODY WALL DEFECTS 10. 11, and up to fetal period. a. Omphalocele i. involves herniation of abdominal viscera through an enlarged umbilical IX. INNERVATION OF THE GUT TUBE ring. ii. may include liver, small, and large Vagal neural crest cells innervate the gut tube. intestines, stomach, spleen, or Additional lumbosacral neural crest cells innervate the gallbladder, are covered by amnion. hindgut. iii. origin of the defect is a failure of the bowel to return to the body cavity from its physiological herniation during the 6th to 10th weeks. Page 8 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 iv. Approximately 15% of live infants have 1. no amnion covering the chromosomal abnormalities. intestines 2. Incidence rate: 1/10,000 3) VITELINE DEFECTS a. Meckel diverticulum or ileal diverticulum i. 2% to 4% of people, a small portion of the vitelline duct persists, forming an outpocketing of the ileum adult approximately 40 to 60 cm from the ileocecal valve on the antimesenteric border of the ileum, does not usually cause any symptoms. Figure 23. Infant omphalocele. v. an abdominal wall defect at the base of the umbilical cord (umbilicus); the infant is born with sac protruding through the defect which contains small intestine, liver, and large intestine. Figure 24. Remnants of the vitelline duct. vi. Failure of the intestine to return after a physiologic herniation. The herniated b.Enterocystoma, Or A Vitelline Cyst loop is covered by an amnion Trangulation Or Volvulus vii. The return of physiologic herniation i. heterotopic pancreatic tissue or gastric happens on the 6th to 10th weeks of mucosa, cause ulceration, bleeding, or gestation even perforation. both ends of the viii. Incidence rate: 2.5/10,000 births vitelline duct transform into fibrous ix. Mortality: 25%. cords, and the middle portion forms a x. Omphalocele is associated with other large cyst. anomalies: c. Umbilical Fistula, Or A Vitelline xi. Cardiac anomalies: 50%. Most i. intestinal loops may twist around the common fibrous strands and become xii. Neural Tube defects: 40% obstructed xiii. Factors increasing the risk of ii. fecal discharge may then be found at omphalocele: the umbilicus ▪ Alcohol 4) GUT ROTATION DEFECTS ▪ Tabacco Malrotation of the intestinal loop may result in ▪ Selective serotonin re-uptake twisting of the intestine [volvulus] and a inhibitors (SSRIs) compromise of the blood supply. ▪ Obesity Normal: , the primary intestinal loop rotates 270° b. Gastroschisis counterclockwise. i. refers to a protrusion of abdominal rotation amounts to 90° only in the colon and contents through the body wall directly cecum are the first portions of the gut to return into the amniotic cavity. from the umbilical cord, and they settle on the ii. it occurs lateral to the umbilicus usually left side of the abdominal cavity. The later on the right, and the defect is most returning loops then move more and more to the likely due to abnormal closure of the right, resulting in a left-sided colon. body wall around the connecting stalk. a. Reversed rotation of the intestinal loop. iii. Volvulus [rotation of the bowel] i. occurs when the primary loop rotates resulting in a compromised blood 90° clockwise. supply may, however, kill large regions of the intestine and lead to fetal death. Page 9 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 ii. transverse colon passes behind the 6) Hindgut Abnormalities duodenum and lies behind the superior a. Rectourethral and rectovaginal fistulas mesenteric artery. i. occur in l/5,000 live births b. Duplications of intestinal loops and cysts ii. caused by abnormalities in formation iii. occur anywhere along the length of the of the cloaca and/or the urorectal gut tube. found in the region of the septum. ileum. iii. For example, if the cloaca is too small or if the urorectal septum does not extend far enough caudally, then opening of the hindgut shifts anteriorly leading to an opening of the hindgut into the urethra or vagina. b. Rectoanal fistulas and atresias i. leave a narrow tube or fibrous remnant connected to the perineal surface. ii. due to misexpression of genes during Figure 25. (A) Abnormal rotation of primary intestinal loop (B) The epithelial—mesenchymal signaling. c. lmperforate anus primary intestinal loop is rotated 90° clockwise (reversed rotation). i. the anal membrane fails to breakdown. 5) GUT ATRESIAS and STENOSES occur anywhere along the intestine. TEST YOUR KNOWLEDGE most occur in the duodenum, fewest occur in the 1. Pancreatic islets consist of alpha, beta, and delta cells, colon, and equal numbers occur in the jejunum which secrete glucagon, insulin, and somatostatin, and ileum [1/1,500 births] respectively. These cells are derived from. Atresia in the upper duodenum is probably due a) mesoderm to a lack of recanalization distal portion b) endoderm duodenum caudally stenosis and Atresia c) ectoderm caused by vascular “accidents” that resulted in d) neuroectoderm compromised blood flow and tissue necrosis in e) neural crest cells a section of the gut resulting in the defects. 2. A 2-month-old baby with severe jaundice also has dark- Accidents caused by malrotation, volvulus, colored urine (deep yellow) and white clay-colored stool. gastroschisis, omphalocele, and other factors, Which of the following disorders might be suspected? misexpression of some HOX genes and of a) Esophageal stenosis genes and receptors in the FGF family result in b) Annular pancreas gut Atresia. c) Hypertrophic pyloric stenosis a. Apple peel atresia d) Extrahepatic biliary atresia i. accounts for 10% of Atresias. e) Duodenal atresia ii. atresia is in the proximal jejunum, and 3. A 28-day-old baby is brought to the physician because the intestine is short, with the portion of projectile vomiting after feeding. Until this time, the distal to the lesion coiled around a baby has had no problems in feeding. On examination, mesenteric remnant. a small knot is palpated at the right costal margin. Which of the following disorders might be suspected? a) Esophageal stenosis b) Annular pancreas c) Hypertrophic pyloric stenosis d) Extrahepatic biliary atresia e) Duodenal atresia 4. Which of the following arteries supplies foregut derivatives of the digestive system? a) Celiac trunk b) Superior mesenteric artery Figure 26. Apple peel atresia, which occurs in the jejunum and accounts c) Inferior mesenteric artery for 10% of bowel atresias. The affected portion of the bowel is coiled d) Right umbilical artery around a remnant of mesentery. e) Intercostal artery Page 10 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 5. The most common type of anorectal malformation 11. Kupffer cells present in the adult liver are derived from is a) mesoderm a) imperforate anus b) endoderm b) anal agenesis c) ectoderm c) anorectal agenesis d) neuroectoderm d) rectal atresia e) neural crest cells e) colonic aganglionosis 12. The simple columnar and stratified columnar epithelia 6. The simple columnar or cuboidal epithelium lining the lining the lower part of the anal canal is derived from extrahepatic biliary ducts is derived from? a) mesoderm a) mesoderm b) endoderm b) endoderm c) ectoderm c) ectoderm d) neuroectoderm d) neuroectoderm e) neural crest cells e) neural crest cells 13. A baby born to a young woman whose pregnancy was 7. A 4-day-old baby boy has not defecated since coming complicated by polyhydramnios was placed in the home from the hospital even though feeding has been intensive care unit because of repeated vomiting normal without any excessive vomiting. Rectal containing bile. The stomach was markedly distended, examination reveals a normal anus, anal canal, and and only small amounts of meconium had passed rectum. However, a large fecal mass is found in the through the anus. What is the most likely diagnosis? colon, and a large release of flatus and feces follows the a) Esophageal stenosis rectal examination. Which of the following conditions b) Annular pancreas would be suspected? c) Hypertrophic pyloric stenosis a) Imperforate anus d) Extrahepatic biliary atresia b) Anal agenesis e) Duodenal atresia c) Anorectal agenesis 14. The ____begins caudal to the liver bud and extends to d) Rectal atresia the junction of the right two-thirds and left third of the e) Colonic Aganglionosis transverse colon in the adult. 8. Which one of the following structures is derived from the a) Foregut midgut? b) Midgut a) Appendix c) Hindgut b) Stomach d) Endoderm c) Liver e) Mesoderm d) Pancreas Matching type e) Sigmoid colon 15. SOXZ A. the small intestine 9. A 3-month-old baby girl presents with a swollen 16. PDX1 B. esophagus and stomach umbilicus that has failed to heal normally. The umbilicus 17. CDXC C. the duodenum drains secretions, and there is passage of fecal material 18. CDXA D. large intestine and rectum through the umbilicus at times. What is the most likely diagnosis? 19. _______ expression upregulates factors in the a) Omphalocele mesoderm that then determine the type of structure that b) Gastroschisis forms from the gut tube, such as the stomach, c) Anal agenesis duodenum, small intestine, etc. d) Ileal diverticulum a) SHH e) Intestinal stenosis b) HOX 10. The midgut loop normally herniates through the primitive c) SOXZ umbilical ring into the extraembryonic coelom during d) CDXC week 6 of development. Failure of the intestinal loops to e) CDXA return to the abdominal cavity by week 11 results in the formation of 20. ___________ is a continuous serous membrane lining a) omphalocele the inner surface of the abdominal cavity from which it is b) gastroschisis reflected onto the viscera. c) anal agenesis a) Plural d) ileal diverticulum b) Pericardial e) intestinal stenosis c) Peritoneum Page 11 of 12 CMED 1D  (004) EMBRYONIC DEVELOPMENT OF GASTROINTESTINAL TRACT DR. GAIL TANAWIT| 01/04/21 d) Perimysium e) Peritonic 21. The free margin of the lesser omentum connecting the duodenum and liver is thickened to form the? a) Epiploic formamen b) ligamentus teres hepatis c) umbilical vein d) Viteline duct e) Portal pedicle 22. __________occurs when the circular and, to a lesser degree, the longitudinal musculature of the stomach in the region of the pylorus hypertrophies. a) Omphalocele b) Pyloric stenosis c) Gastroschisis d) Apple peel atresia e) Megacolon 23. It involves herniation of abdominal viscera through an enlarged umbilical ring. a) Retrocolic hernia b) volvulus c) Omphalocele d) Billiary atresia e) Pyloric stenosis 24. True or False: Retinoic acid is more concentrated in the pharynx than in the colon. Identify 25. Forms the dorsal mesentery of the stomach. ANSWERS 1.B 2.D 3.C 4.A 5.C 6.B 7.E 8.A 9.D 10.A 11.A 12.C 13.E 14.B 15.B 16.C 17.A 18.D 19.A 20.C 21.D 22.B 23.C 24.FALSE 25.DORSALMESOGASTRUM REFERENCES 1. PPT - Doc Gail Tanawit 2. Langman's Medical Embryology by T.W. Sadler. 14th EDITION, Chapter 15:Digestive Sytem. Pages 230-254 Page 12 of 12 CMED 1D