Embryo

Question 1

what initiates specification of the gut?

Answer 1

retinoic acid gradient that causes TFs expressed in different regions of the tube

Question 2

SOX2 specifies

Answer 2

esophagus

Question 3

PDX2 specifies

Answer 3

duodenum and pancreas

Question 4

CDXC specifies

Answer 4

small intestine

Question 5

CDXA specifies

Answer 5

large intestine

Question 6

what else is required for specification of gut tube into different components?

Answer 6

interaction b/w epithelium and mesenchyme initiated by SHH

Question 7

what does the endoderm become?

Answer 7

epithelial lining and glands

Question 8

what does the splanchnic mesoderm become?

Answer 8

lamina propria, submucosa, muscularis layers, serosa/adventitia

Question 9

what supplies foregut?

Answer 9

celiac A

Question 10

what supplies midgut?

Answer 10

SMA

Question 11

what supplies hindgut?

Answer 11

IMA

Question 12

where are preganglionic cell bodies for foregut and midgut?

Answer 12

brainstem

Question 13

where are preganglionic cell bodies for hindgut?

Answer 13

S2-4

Question 14

nerve of the foregut and midgut

Answer 14

vagus N

Question 15

nerve of the hindgut

Answer 15

pelvic splanchnic N

Question 16

tracheoesophageal fistula

Answer 16

i. lung buds develop from an outgrowth of the esophagus
1. should eventually lose the connection here except for in one area where you can regulate airflow at the tracheoesophageal junction
2. if the opening does not close, then we get a tracheoesophageal fistula
a. this is when we have an inappropriate connection with the esophagus somewhere along the trachea
b. often get atresia of the esophagus—the esophagus ends in a blind pouch

Question 17

esophageal stenosis or atresia

Answer 17

1. narrow or occluded esophagus due to incomplete recanalization, usually found in the lower 1/3
2. may also be caused by vascular abnormalities or compromised blood flow

Question 18

esophageal replacement

Answer 18

1. the majority of esophageal procedures are performed on infants/children and are done for congenital esophageal atresia or acquired caustic strictures
2. successful esophageal anastomoses may be performed in those few with long gap esophageal atresia b/w the proximal and distal esophageal remnants

Question 19

colon interposition

Answer 19

• type of esophageal replacement
• section of colon is taken from normal position and transposed with its blood supply in tact into the chest, where it is joined by the esophagus above and the stomach below

Question 20

gastric tube esophagoplasty

Answer 20

• type of esophageal replacement

- longitudinal segment is taken from stomach, which is swung up into the chest and joined to the esophagus

Question 21

gastric transposition

Answer 21

• type of esophageal replacement

- whole stomach is freed, mobilized, and moved into the chest and attached to the upper end of the esophagus

Question 22

diverticulum of the foregut

Answer 22

i. liver diverticulum
ii. cystic diverticulum
iii. dorsal pancreatic diverticulum
iv. ventral pancreatic diverticulum

Question 23

growth of stomach

Answer 23

i. dorsal surface grows faster than ventral surface (causes c shape)
ii. the abdominal esophagus and stomach start as a straight tube suspended by dorsal and ventral mesentery
1. the dorsal (left) side of the tube grows rapidly expands and there is a CW rotation of 90 degrees
2. rotation of the stomach causes:
a. left side to lie anterior, right side to become posterior
b. left vagus becomes the anterior vagal trunk, right vagus becomes the posterior vagal trunk

Question 24

hypertrophic pyloric stenosis

Answer 24

1. usually presents 2-3 weeks after birth
2. pyloric sphincter becomes overgrown
   a. doesn’t occur immediately after birth
   b. child comes in with non bilious (non green) projectile vomiting
3. clinical: scaphoid stomach—distended
   a. also can feel an olive sized mass right of midline which is pyloric sphincter

Question 25

stenosis and atresia of the duodenum

Answer 25

1. usually, recanalization should occur to reopen the gut tube after development 2. stenosis—occur in 3 or 4 part 3. atresia—occur in 2 or 3 part a. bile will get into this chyme, so it will be vomited green

Question 26

double bubble sign

Answer 26

gas distended stomach and proximal duodenum with no distal gas

Question 27

where does the liver develop?

Answer 27

ventral mesentery

Question 28

molecular regulation of the liver

Answer 28

a. all foregut endoderm has the potential to express liver specific genes and to differentiate into liver tissue b. expression is blocked by unknown signals from the trunk mesoderm and ectoderm, restrict hepatic development in posterior endoderm i. action of these inhibiting factors is blocked in the area of the liver by FGF2 secreted by cardiac mesoderm and BMPs secreted by the septum transversum ii. cardiac mesoderm/septum transversum instruct the gut endoderm to express liver specific genes

Question 29

ductus venosus

Answer 29

shunts a portion of the left umbilical vein blood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.

Question 30

ligamentum venosum

Answer 30

fibrous remnant of the ductus venosus

Question 31

ligamentum teres hepatis

Answer 31

obliterated left umbilical vein

Question 32

Extrahepatic biliary atresia

Answer 32

a. Incomplete canalization of the bile duct b. 1/15000 live births c. can’t get bile from liver down into the GI system i. jaundice—high levels of bilirubin in bloodstream ii. dark urine—bilirubin filtered by kidney and excreted in urine iii. pale stool—no bile or bilirubin is being emptied into the intestine d. TX: surgical correction or transplant

Question 33

where does the gallbladder and bile ducts develop?

Answer 33

ventral mesentery

Question 34

where does the pancreas develop?

Answer 34

ventral and dorsal mesentery

Question 35

PDX1

Answer 35

pancreas and duodenum

Question 36

paired homeobox genes specify

Answer 36

endocrine cell lineages

Question 37

PAX4

Answer 37

cells secreting insulin, somatostatin, and pancreatic polypeptide

Question 38

PAX6

Answer 38

cells secreting glucagon

Question 39

islets of langerhans

Answer 39

3rd fetal month

Question 40

insulin secretion

Answer 40

5th fetal month

Question 41

what causes the 2 parts of the pancreas to fuse?

Answer 41

stomach rotation

Question 42

annular pancreas

Answer 42

a. Ventral and dorsal pancreatic buds form a ring around the duodenum b. Presents as duodenal obstruction

Question 43

accessory or ectopic pancreatic tissue

Answer 43

a. Can be found from distal esophagus thru the primary intestinal loop (roughly distal part of transverse colon) b. Most common in stomach or ileum (ileal or Meckel’s diverticulum)

Question 44

Gut atresias and stenosis

Answer 44

i. May occur anywhere along intestine ii. In upper duodenum—usually due to failure to recanalize iii. Caudal to duodenum—due to vascular compromise

Question 45

apple peel atresia

Answer 45

1. 10% of all atresias 2. occurs in proximal jejunum 3. intestine is short and portion distal to defect is coiled around mesenteric remnant a. part of gut has died and has tobe removed 4. associated with low body weight and other abnormalities

Question 46

rotation and fixation of the midgut

Answer 46

i. rapid growth of midgut starts at about 6 weeks ii. produces a normal physiologic herniation iii. gut loops into the umbilical cord iv. as this happen, the loop rotates 90 degrees CCW around SMA v. at about the 10th week, the herniated loops return to the abdominal cavity and rotate an additional 180 degrees vi. returns to abdominal cavity

Question 47

malrotation

Answer 47

1. partial rotation only 2. abnormally positioned viscera 3. increased risk of entrapment of portions of the intestine 4. usually presents within first week as duodenal obstruction with bilious vomiting 5. infants—recurrent abdominal pain, intestinal obstruction, malabsorption/diarrhea, peritonitis/septic shock, solid food intolerance, common bile duct obstruction, abdominal distention, and failure to thrive

Question 48

ladd's bands

Answer 48

a. connection b/w gut tube and abdominal wall that shouldn’t be there b. this may compress a part of the gut tube that is underneath the Ladd band

Question 49

volvulus

Answer 49

1. abnormal twisting of the intestine causing obstruction | 2. compromises the intestines or the blood flow

Question 50

intussusception

Answer 50

1. enfolding of one segment of the intestine within another 2. characterized and initially presents with recurring attacks of cramping abdominal pain that gradually become more painful

Question 51

omphalocele

Answer 51

i. herniation of abdominal contents thru enlarged umbilical ring 1. this Is normal if it is temporary 2. the gut should return into the abdomen as the embryo grows ii. midgut does not return to the abdominal cavity iii. pale, shiny sac protrudes from base of umbilical cord

Question 52

gastroschisis

Answer 52

i. failure of anterior abdominal wall musculature to close during folding ii. gut contents not surrounded by membrane iii. 1-2/10000 but frequency increasing in young women possibly due to drug use iv. not associated with chromosomal abnormalities or malformations v. survival rate is excellent

Question 53

prune belly syndrome common triad of features

Answer 53

1. anterior abdominal wall—musculature is deficient or absent 2. urinary tract anomalies—mega-ureters, large bladder 3. bilateral cryptorchidism—undescended testes

Question 54

2 hypotheses of etiology of prune belly syndrome

Answer 54

1. urinary tract obstruction—causes overdistention of the bladder and upper urinary tract which stretches the abdominal wall and causes damage to abdominal musculature and interferes with descent of testicles 2. primary mesodermal developmental defect—an insult b/w 6-10 weeks gestation which disrupts the development of the intermediate and lateral plate mesoderm which give rise to both abdominal wall and genitourinary tract

Question 55

ill diverticulum

Answer 55

i. Meckel’s diverticulum ii. Remnant of vitelline duct iii. Asymptomatic iv. Gastric or pancreatic tissue in the diverticulum v. Failure of vitelline duct to close vi. Rule of 2’s 1. 2% prominence, 2:1 female predominance, location 2 feet proximal to ileocecal valve in adults, half of those who symptomatic are younger than 2 years old vii. causes fecal discharge thru umbilicus

Question 56

hirschsprung's disease

Answer 56

i. Congenital aganglionic megacolon, is a motor disorder of the colon that causes a functional intestinal obstruction ii. Both plexuses are affected iii. Occurs in 1/5000 infants with male to female predominance of 4:1 iv. Pathogenesis of the disease is failure of migration of the neural crest cells that form the colonic ganglion cells v. Without PS innervation, the colon cannot relax or undergo peristalsis, which causes a functional obstruction

Question 57

tx of HD

Answer 57

1. Surgery is only proven, effective tx for HD 2. Procedure is called pull through surgery and involves removing the section of the colon that has no ganglia cells, then connecting the remaining healthy end of colon to rectum

Question 58

imperforate anus

Answer 58

1. Malformation of the anorectal region that may occur in several forms 2. The recutm may end in a blind pouch that does not connect with the external environment, or it may have openings to urethra, bladder, or vagina 3. Stenosis, or narrowing of anus, or absence of anus may be present 4. Symptoms: a. Absence or misplaced anal opening b. Anal opening very near the vaginal opening in the female c. No passage of first stool within 24-48 hours d. Stool passed by vagina, scrotum, penis e. Abdominal distention

Question 59

Anorectal malformations are on a spectrum of high or low

Answer 59

1. Anal canal ends as bling pouch below pelvic diaphragm—LOW a. Anal agenesis b. Rectum thru diaphragm so have some skeletal muscle we can use for fecal continence 2. Rectum ends as blind pouch above the pelvic diaphragm—HIGH a. No muscle to use to control