Development of the Alimentary System

Question 1

Omphaloceles

Answer 1

Large swelling in the umbilical cord covered in amnion because the intestinal loop failed to return to the abdominal cavity and stayed in the umbilical cord.

Question 2

Gastroischisis

Answer 2

Defect in the anterior abdominal wall allows extrusion of abdominal viscera just hanging outside the body.

Question 3

Ileal (Meckel’s) diverticulum

Answer 3

Outpouching on the ventral border of the ileum close to the ileocecal junction because a remnant of the vitelline/omphaloenteric duct/yolk stalk persists.

Usually degenerates, but may get an ulcer, get inflamed, have a fistula going into the umbilicus, vitelline cysts, volvulus, fibrous cord.

Question 4

Development of imperforate anus

Answer 4

Persistent anal membrane separates the anal canal form the exterior.

Results in many anorectal malformations.

Question 5

Anal agenesis

Answer 5

Anal canal ends blindly or ends with a fistula to the perineum due to failure of the urorectal septum to separate the cloaca.

Question 6

Anal stenosis

Answer 6

Canal is narrowed because the urorectal septum grew too far dorsally

Question 7

Anorectal agenesis

Answer 7

Most common anorectal malformation.

May end blindly or have a fistula to the bladder (rectovesicle fistula) or urethra (rectourethral fistula) or vagina (rectovaginal fistula), due to abnormal formation of the urorectal septum.

Question 8

Megacolon (HIrschsprung’s disease)

Answer 8

Absence of autonomic ganglia (myenteric & submucosal plexus) of colon causes severe dilation of part of the colon (megacolon) as the bolus tries to move down.

Results because neural crest cells fail to migrate caudally.

Question 9

Annular pancreas

Answer 9

The ventral pancreatic bud rotates in the wrong direction, causing it to fuse with the dorsal bud ventrally and dorsally –> pancreas tissue encircles compressing the duodenum.

May be associated with duodenal atresia.

Question 10

Duodenal atresia

Answer 10

The duodenum doesn’t recanalize –> “double bubble” sign on an ultrasound

Question 11

Duodenal stenosis

Answer 11

Incomplete recanalization or annular pancreas constricts the duodenal opening

Question 12

Hypertrophic pyloris stenosis (HPS)

Answer 12

Hypertrophy of the circular smooth muscle at the pyloric sphincter narrows the pyloric lumen -> obstructs food passage

> projectile vomit without bile

Question 13

Esophageal atresia

Answer 13

Tracheoesophageal septum deviates too far dorsally, causing the esophagus to end blindly.

Associated with:
VACTREL
Respiratory distress
Polyhydramnios: excess amniotic fluid due to inability to swallow

Question 14

Esophageal stenosis - what is it and what is it caused by?

Answer 14

Narrowing of the esophagela lumen due to incomplete recanalization

Question 15

Esophageal cysts/webbing due to

Answer 15

Incomplete recanalization

Question 16

Short esophagus can cause what type of hernia?

Answer 16

Congenital hiatal hernia- stomach displaced through the esophageal hiatus

Question 17

Manifestations of hypertrophic pyloric stenosis in infants

Answer 17

• Projectile vomiting (no -bile)
• Dehydration
• May come with esophageal atresia

Question 18

Why is there no bile in the vomit of infants with hypertrophic pyloric stenosis?

Answer 18

The bile duct is caudal of the pyloric region of the stomach .

Question 19

Sign of duodenal atresia

Answer 19

Infant vomits hours after birth and it contains bile.

Question 20

Does vomit from annular pancreas contain bile?

Answer 20

Yes.

Question 21

Congenital Umbilical Hernia

Answer 21

The gut went in but herniates back out into the umbilical area, but it’s covered with skin.

3x more common in women

Question 22

What is the cause of aganglionic megacolon?

Answer 22

Failure of neural crest cells to migrate into the wall of the colon in the 5th-7th wks.

Question 23

Rectal atresia

Answer 23

Rectum and anal canal are separated by a wedge of fibrous tissue.

Occurs because of abnormal recanalization or compromised blood supply.

Question 24

Most common anorectal malformation

Answer 24

Anorectal agenesis.

Question 25

The spleen is derived from

Answer 25

Mesoderm.

It is a derivative of the dorsal mesentery.

Question 26

What are the two types of tissue that Meckel’s diverticulum might contain?

Answer 26

Gastric mucosa and pancreatic tissue

Question 27

Inability to pass meconium means

Answer 27

Fetal bowel is obstructed, probably due to midgut volvulus (intestines are twisted)

Question 28

What is the most common cause of severe rectal bleeding in the pediatric age group?

Answer 28

Ileal (Meckel’s) diverticulum