Suggested readings from Langman's Medical Embryology (13th. ed.): Ch 15, pp. 225-249 Suggested readings from Langman's Medical Embryology (12th. ed.): Ch 15, pp. 208-231 Suggested readings from Langman's Medical Embryology (11th. ed.): Ch. 14, pp. 209-233

Duke LEARNING RESOURCES EB4: Gut Development Session

Click here to launch the Simbryo GI Development animation (and some really trippy music -you'll understand once the window opens...)

I. Overview

A. Formation of the primitive gut tube

B. Basic subdivisions of the gut tube

FOREGUT

MIDGUT

HINDGUT

C. Definitive subdivisions of the gut tube

D. Cranio-caudal patterning of the gut tube

E. Radial patterning of the gut tube

This occlusion and re-canalization process occurs THROUGHOUT the tube (esophagus to anus) and errors in this process can occur in anywhere along the tube resulting in stenosis (narrowing of the lumen or even outright occlusion) in that region.

F. Mesenteries of the gut tube (refer to the figure on the previous page)

A summary of what is retroperitoneal, intraperitoneal, or secondarily retroperitoneal in the adult:

II. Derivatives of the foregut:

A. Esophagus

Clinical considerations

B. Stomach

Clinical Considerations

C. Liver

D. Pancreas

Errors in the fusion process can result in an annular pancreas that wraps around the duodenum, which can cause obstruction the symptoms of which would be similar to pyloric stenosis except that the vomit may be bilious and there would NOT be a palpable knot in the epigastric region.

E. Proximal or upper duodenum

III. Derviatives of the midgut

A. Distal or lower duodenum

Failure to recanalize the duodenum can result in stenosis (narrowing) or atresia (complete blockage), the symptoms of which would be bilious projectile vomiting an hour or so after feeding.

B. Jejunum, ileum, cecum, appendix, ascending colon, and proximal 2/3 of transverse colon

Failure to obliterate the vitelline duct can result in diverticula (out pouching of the gut tube) called Meckel's diverticula,vitelline cysts or vitelline fistulas (a connection of the small intestine to the skin). These will often be attached at one end to the umbilicus and at the other end to the ileum.

Failure to pull all of the gut contents back into the abdominal cavity or to completely close off the ventral body wall at the umbilicus can result in an oomphalocoele, where the gut contents herniate out of the body wall.

Defects and variations in rotation can cause a variety of aberrant anatomical positions of the viscera that are often asymptomatic, but important to appreciate when trying to diagnose and/or treat gastrointestinal problems (e.g. abnormal positioning of the appendix due to malrotation should be considered when trying to diagnose appendicitis). Malrotation can also cause twisting or volvulus of the gut tube resulting in stenosis and/or ischemia.

III. Derivatives of the hindgut

Failure of the cloacal membrane to break down can result in an imperforate anus.

Failure to generate enough mesoderm during gastrulation can result in anal atresia in which there is insufficient development of the wall (namely the smooth muscle and connective tissue) of the rectoanal canal Failures in the division of the cloaca (usually accompanied by anal atresia) can lead to a variety of aberrant connections of the rectal canal to portions of the urogenital tract.

Failure of neural crest cells to migrate and/or differentiate into neurons in a portion of gut will result in an aganglionic segment (missing submucosal and myenteric ganglia). The main function of these ganglia is to allow local relaxation in the wall of the gut tube, so the aganglionic segment is tonically contracted, leading to obstruction. For a variety of reasons, the distal portions of the colon are most susceptible to this problem, leading to a condition known as Hirschsprung disease or congenital megacolon. The affected individuals often present with a very distended abdomen due to the presence of an aganglionic segment of colon (usually in the sigmoid colon) that causes a blockage and then backup of feces (and massive enlargement) in the descending colon.

Practice Questions

1. Which of the following is NOT derived at least in part from the midgut?

ANSWER

3. During development of the gut:

ANSWER

5. Meckel's diverticula, vitelline cysts, or vitelline fistulas are most commonly found in association with:

ANSWER

6. During development of the gut:

ANSWER

7. The greater omentum is derived from the:

ANSWER

Questions 8 and 9 refer to the following case: A one-week-old male infant is brought in by his parents who report bilious projectile vomiting about 2 hours after each feeding. The child has not gained much weight since birth and the parents comment that the child's diapers are not particularly soiled or when they are changed. On physical exam the child is lethargic and exhibits signs of dehydration. The heart and breathing rates are somewhat elevated, but otherwise the heart and lungs appear normal. On physical exam, the abdomen is unremarkable

8. Which of the following conditions best accounts for the infant's signs and symptoms?

ANSWER

9. The most likely cause of the infant's condition is:

ANSWER

For items 10 12 below, select the one lettered option from the following list that is most closely associated with each numbered item below. Options in the list may be used once, more than once, or not at all. a. ventral mesentery of the liver b. dorsal mesentery of liver / ventral mesentery of stomach c. dorsal mesentery of stomach e. vitelline duct f. allantois

10. urachal cyst ANSWER

11. falciform ligament ANSWER

12. lesser omentum ANSWER

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Updated 10/13/15 - Velkey

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Duke Embryology - Gut Development