Updated: 11/11/2020

GI Embryology

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Questions
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Evidence
5 5
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Topic
Overview
  • Developmental derivatives
    • foregut (supplied by celiac trunk) → pharynx to duodenum
    • midgut (supplied by the superior mesentric artery) → duodenum to transverse colon
    • hindgut (supplied by the inferior mesentric artery)→ distal transverse colon to rectum
  • GI embryologic timeline
    • week 6
      • midgut herniates through umbilical ring
    • week 10-11
      • rotates 270 degrees counterclockwise around SMA as it returns to the abdominal cavity 
        • abnormal rotation and fixation of the midgut during early fetal life may result in obstruction and volvulus (which may lead to intestinal ischemia)  
Pathology
  • Anterior abdominal wall defects due to failure of
    • rostral fold 
      • sternal defects result 
    • lateral fold  
      • omphalocele
        • abdominal contents (stomach, liver, intestines, etc.) protrude through umbilical cord and persist outside of the body but covered by peritoneum
        • associated with trisomy 13 and 18
      • gastoschisis
        • failure of lateral body folds to fuse, resulting in extrusion of intestines through umbilical ring but not covered by peritoneum
    • caudal fold 
      • bladder extrophy is the protrusion of the anterior bladder through the lower abdominal wall
  • Duodenal atresia 
    • due to failure to recanalize lumen of intestines 
    • associated with trisomy 21
    • "double bubble" sign
    • NOTE: atresia is occlusion of the lumen of the intestines and stenosis is narrowing of the lumen
  • Jejunal, ileal, and colonic atresia
    • due to vascular accident ("apple peel/corkscrew" atresia   
    • segment of bowel wrapped around a remnant of mesentary
  • Congenital pyloric stenosis  
    • hypertrophy of muscalaris externa causing the pylorus lumen to narrow 
      • palpable "olive" mass in epigastric region
      • food obstructs in pyloric region
      • nonbilious and projectile vomiting at about 2 weeks of age
    • treatment: surgery
    • incidence: 1/600; mainly first born males
  • Pancreas divisum- failed fusion of the ventral and dorsal pancreatic buds

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Questions (9)
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(M1.EB.17.4707) A 1-month-old boy is brought to the emergency department by his parents for recent episodes of non-bilious projectile vomiting and refusal to eat. The boy had no problem with passing meconium or eating at birth; he only started having these episodes at 3 weeks old. Further history reveals that the patient is a first born male and that the boy’s mother was treated with erythromycin for an infection late in the third trimester. Physical exam reveals a palpable mass in the epigastrum. Which of the following mechanisms is likely responsible for this patient’s disorder? Tested Concept

QID: 108429
1

Defect of lumen recanalization

11%

(25/225)

2

Hypertrophy of smooth muscle

66%

(148/225)

3

Intestinal vascular accident

3%

(6/225)

4

Neural crest cell migration failure

10%

(22/225)

5

Pancreatic fusion abnormality

8%

(18/225)

M 1 B

Select Answer to see Preferred Response

(M1.EB.15.26) A 2-week-old boy has developed bilious vomiting. He was born via cesarean section at term. On physical exam, his pulse is 140/min, blood pressure is 80/50 mmHg, and respirations are 40/min. His abdomen appears distended and appears diffusely tender to palpation. Abdominal imaging is obtained (Figures A). Which of the following describes the mechanism that caused this child's disorder? Tested Concept

QID: 101048
FIGURES:
1

Ischemia-reperfusion injury in premature neonate

6%

(1/16)

2

Telescoping segment of bowel

12%

(2/16)

3

Abnormal rotation of the midgut

62%

(10/16)

4

Hypertrophy of the pylorus

6%

(1/16)

5

Partial absence of ganglion cells in large intestine

12%

(2/16)

M 1 D

Select Answer to see Preferred Response

(M1.EB.14.17) A 1-week-old male is brought by his mother to their pediatrician's office with complaints of a 3 day history of feeding intolerance and frequent bilious vomiting. An upper GI contrast radiograph is obtained (Figure A) and shows obstruction of the 3rd part of the duodenum with displacement of the duodenojejunal junction to the right of midline. Which of the following mechanisms is responsible for this infant's condition? Tested Concept

QID: 101911
FIGURES:
1

Failure to recanalize the lumen of the duodenum

42%

(11/26)

2

Hypertrophy of the muscularis externa at the pylorus

12%

(3/26)

3

Failed fusion of lateral body folds

0%

(0/26)

4

Intestinal malrotation

31%

(8/26)

5

Failed fusion of the dorsal and ventral pancreatic buds

12%

(3/26)

M 1 D

Select Answer to see Preferred Response

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Evidence (5)
Topic COMMENTS (22)
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