2: Development Of The GI System

Question 1

What action forms the foregut, midgut, and hindgut?

Answer 1

Craniocaudal folding of the endoderm

Question 2

Six organs formed by foregut

Answer 2

1. Esophagus
2. Stomach
3. Liver
4. Gallbladder
5. Pancreas
6. Upper duodenum

Question 3

Seven organs formed by midgut

Answer 3

1. Lower duodenum
2. Jejunum
3. Ileum
4. Cecum
5. Appendix
6. Ascending colon
7. Prox 2/3 of transverse colon

Question 4

Five organs formed by hindgut

Answer 4

1. Distal 1/3 of transverse colon
2. Descending colon
3. Sigmoid colon
4. Rectum
5. Upper 2/3 anal canal

Question 5

BS to foregut, midgut, and hindgut

Answer 5

Foregut: celiac trunk
Midgut: superior mesenteric A
Hindgut: inferior mesenteric A

Question 6

What forms the vitelline duct

Answer 6

Yolk sac opening

Question 7

What the three germ layers of the GI tract form

Answer 7

Endoderm: mucosal ep, GI glands
Splanchnic mesoderm: CT, vasculature, smooth muscle walls
Ectoderm: enteric ganglia/nerves/glia, epithelium of lower 1/3 of anus

Question 8

Two main functions of peritoneum

Answer 8

1. Produces fluid to lubricate peritoneum and minimize friction
2. Produce Abs, mobilize leukocytes, and localize infection

Question 9

Boundaries of the epiploic foramen

Answer 9

Hepatoduodenal lig, 1st part of duodenum, peritoneum covering IVC and from liver to IVC

Question 10

Three ligaments that form the greater omentum

Answer 10

1. Gastrosplenic
2. Gastrocolic
3. Splenorenal

Question 11

Two ligaments that form the lesser omentum

Answer 11

1. Hepatoduodenal

2. Hepatogastric

Question 12

Peritoneal ligaments

Answer 12

regional mesenteries connecting one organ with another or to the abdominal wall (named by organs they connect)

Question 13

3 Peritoneal ligaments besides the ones that form the omenta

Answer 13

1. Gastrophrenic
2. Transverse mesocolon
3. Phrenocolic

Question 14

Intraperitoneal organs

Answer 14

Are suspended by mesentery inside the peritoneum

Question 15

List of organs that are retroperitoneal

Answer 15

1. Suprarenal glands
2. Aorta and IVC
3. Duodenum (2nd and 3rd part)
4. Pancreas
5. Ureters
6. Colon
7. Kidneys
8. Esophagus
9. Rectum
   (SAD PUCKER)

Question 16

Secondarily retroperitoneal

Answer 16

Organs that were initially suspended in mesentery but then fused with body wall

Question 17

Three organs that are secondarily retroperitoneal

Answer 17

Colon, duodenum, bulk of pancreas

Question 18

Foregut mesentery vs mid and hindgut

Answer 18

Foregut: dorsal + ventral mesogastrium; mid and hindgut only have 1 mesentery

Question 19

Hypertrophic pyloric stenosis

Answer 19

Narrow pyloric lumen due to muscle hypertrophy around it

Question 20

What causes hypertrophic pyloric stenosis?

Answer 20

faulty NCC migration-> ganglion cells of enteric NS not properly populated -> Inability of sphincter to relax

Question 21

How many infants are born with hypertrophic pyloric stenosis?

Answer 21

1 in 500 infants

Question 22

Presentation of hypertrophic pyloric stenosis

Answer 22

Presents within a few months of birth with a palpable olive/mass at right costal margin, projectile non-bilious vomiting after feeding, few/small stools, failure to gain weight

Question 23

Congenital anomalies of the liver

Answer 23

Are very rare

Question 24

Biliary atresia etiology

Answer 24

Obliteration of bile duct or inflammation replaces duct with fibrotic tissue

Question 25

Presentation of biliary atresia in infants

Answer 25

Immediate onset of progressive jaundice, white clay colored stools, dark urine, poor prognosis (12-19 month lifespan)

Question 26

How many pts have accessory pancreatic ducts?

Answer 26

33%

Question 27

Pancreatic divisum

Answer 27

Ventral and dorsal pancreatic buds fail to fuse

Question 28

Presentation of pancreatic divisum

Answer 28

Mostly asymptomatic, some pts prone to abdominal pain or pancreatitis

Question 29

Annular pancreas

Answer 29

Pancreatic ring around 2nd part of duodenum due to poor migration of pancreas

Question 30

Presentation of annular pancreas

Answer 30

Duodenal obstruction/stenosis -> bilious vomiting, low birth weight

Question 31

What causes imperforate anus

Answer 31

Persistent anal membrane

Question 32

What causes low, intermediate, or high distinction in imperforate anus?

Answer 32

Levator ani muscle positioning

Question 33

Other name for Hirschsprung’s disease

Answer 33

Congenital Aganglionic Megacolon

Question 34

What causes Hirschsprung’s disease

Answer 34

Absence of ganglionic plexus -> colon fails to relax -> lack of peristalsis; due to failure of NCC migration

Question 35

Presentation of Hirschsprung’s disease

Answer 35

Intestinal wall hypertrophy proximal to a ganglionic segment, abnormal colonic dilation or distention (megacolon), failure to pass meconium (first BM of a newborn), poor feeding, abdominal distention, vomiting, jaundice

Question 36

Hirschsprung’s genetic mutation

Answer 36

RET gene

Question 37

Hirschsprung’s is the colon equivalent to what other disease?

Answer 37

Achalasia

Question 38

Hirschsprung’s in order children

Answer 38

Constipation, swollen belly, malnutrition

Question 39

Three types of Hirschsprung’s based on how much colon is affected

Answer 39

1. Short segment disease (85% of cases): rectosigmoid region 2. Long segment disease: rectosigmoid region -> splenic flexure 3. Total colonic aganglionosis: affects entire colon

Question 40

Dx for Hirschsprung’s

Answer 40

Delayed BM 48ish hrs after birth, rectal biopsy, barium enema

Question 41

Tx for Hirschsprung’s

Answer 41

Surgical removal of affected colon segment, pull through ganglionic colon segments