2. GI embryology

Question 1

normal gastrointestinal embryology - structures that give rise to

Answer 1

1. Foregut –> pharynx to duodenum ( including liver , gallbladder and pancrease)
2. Midgut —> duodenum to proximal 2/3 of transverse colon
3. Hindgut –> distal 1/3 transverse colon to anal canal above pectinate line

Question 2

the primitive gut tube is formed from

Answer 2

the incorporation of the dorsal part of the yolk sac into embryo due to craniocaudal folding and lateral folding of the embryo –> it extends drom oropharyngeal membrane and is divided into : 1. Foregut 2. Midgut 3. Hindgut

Question 3

primitive gut tube epithelial behaviour

Answer 3

early in development –> epithelial lining of the gut tube proliferates rapidly and obliterates the lumen –> later, recanalization occur

Question 4

Midgut development: (and times

Answer 4

6th week—physiologic midgut herniates through umbilical ring
10th week—returns to abdominal cavity + rotates around superior mesenteric artery (SMA),
total 270° counterclockwise

Question 5

Ventral wall defects - types and result

Answer 5

Developmental defects due to failure of:
ƒƒ Rostral fold closure—sternal defects
ƒƒ Lateral fold closure—omphalocele,
gastroschisis
ƒƒ Caudal fold closure—bladder exstrophy

Question 6

Gastroschisis

Answer 6

extrusion of abdominal contents
through abdominal folds (typically right of
umbilicus); not covered by peritoneum

Question 7

Omphalocele

Answer 7

persistence of herniation of
abdominal contents into umbilical cord,
sealed by peritoneum

Question 8

• A patient has a malformed gastrointestinal tract from pharynx to duodenum. What part of the embryo had impaired development?

Answer 8

Foregut

Question 9

• In a patient with a hiatal hernia, the herniated structure was originally derived from the ____ (foregut/midgut/hindgut).

Answer 9

Foregut (herniation of the proximal stomach through the diaphragm)

Question 10

• A developing embryo suffers a malfunction of the midgut. Which region of the gastrointestinal tract will be impacted?

Answer 10

Duodenum to the transverse colon

Question 11

• The part of the colon supplied by both the hepatic and splenic flexures is derived from the ____ (foregut/midgut/hindgut).

Answer 11

Midgut (the transverse colon is supplied by both the hepatic and splenic flexures)

Question 12

• A developing embryo suffers damage to the hindgut. As an adult, what structures of the GI tract will be affected?

Answer 12

The distal transverse colon to the rectum

Question 13

• An extrusion of abdominal contents not covered by the peritoneum is found on a newborn undergoing surgery. Name this diagnosis.

Answer 13

Gastroschisis (failure of the lateral body folds to fuse)

Question 14

• A baby with bladder exstrophy presents to the clinic. What type of folds failed to close properly during embryologic development?

Answer 14

Caudal folds

Question 15

• A baby presents with sternal defects. Failure of what type of folds to close properly caused this clinical scenario?

Answer 15

Rostral folds

Question 16

• An extrusion of abdominal contents into the umbilical cord is covered by the peritoneum on a newborn having surgery. Name this diagnosis.

Answer 16

Omphalocele (sealed by peritoneum)

Question 17

• In the sixth week, the midgut herniates through this structure, then returns to the abdominal cavity (week 10) and rotates around the SMA.

Answer 17

Umbilical ring

Question 18

• A newborn presents with severe abdominal distention. Around which artery is the baby’s midgut malrotated?

Answer 18

Superior mesenteric artery

Question 19

• A baby is born with trisomy 21 and diagnosed with duodenal atresia. How would you explain this GI tract malformation to the parents?

Answer 19

Failure of the duodenum to recanalize

Question 20

• An infant fails to pass meconium at birth. X-ray shows apple-peel atresia of the lower GI tract. What most likely happened in utero?

Answer 20

Vascular accident causing jejunal, ileal, and colonic atresia (characteristic apple-peel atresia on x-ray)