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Anatomy II Exam I > GI Embryology > Flashcards

GI Embryology Flashcards

1
Q

How is specification done in the gut tube?

A

-RA gradient that causes transcription factors to be expressed in different regions

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2
Q

What TF induce what structures?

A
  • SOX2 -> esophagus
  • PDX1 -> duodenum and pancreas
  • CDXC -> SI
  • CDXA -> LI

Requires interaction between the endoderm and mesenchyme intimated by SHH

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3
Q

What does gut tube development involve?

A
  • continuous elongation
  • herniation past the body wall into umbilical cord
  • rotation and folding for efficient packing
  • histiogenesis and further maturation of epithelial lining
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4
Q

Where does mesentery come from?

A

-dorsal mesentery are reflections of parietal peritoneum onto gut tube

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5
Q

Gut tube is a single _________ structure. _____ peritoneal cavities are of equal size.

A
  • Midline

- 2

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6
Q

What are the three segmentations of the gut tube?

A
  • foregut
  • midgut
  • hindgut

-innervation and blood supply to these segments is strongly patterned

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7
Q

What structures are in the foregut?

A
  • esophagus
  • stomach and 1/2 duodenum
  • liver
  • gallbladder
  • pancreas
  • spleen
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8
Q

What structures are in the midgut?

A
  • 1/2 duodenum
  • jejunum
  • ileum
  • cecum and appendix
  • ascending colon
  • 2/3 transverse colon
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9
Q

What structures are in the hindgut?

A
  • 1/3 transverse colon
  • descending colon
  • sigmoid colon
  • upper part of anal canal
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10
Q

What are the vascular supplies for the 3 gut segments?

A

Foregut: celiac artery

Midgut: superior mesenteric artery

Hindgut: inferior mesenteric artery

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11
Q

What is the innervation to the hindgut?

A

-least splanchnic nerve to the Aorticopulmonary-renal plexus

  • post ganglionic a follow the arteries
  • lumbar splanchnic a from L1-L2 to inferior mesenteric plexus
  • post-ganglionics follow the arteries
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12
Q

What are the. Preganglionic cell bodies, nerve, and location of ganglia of the foregut and midgut?

A
  • brainstem
  • vagus nerve
  • organ walls
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13
Q

What are the preganglionic cell bodies, nerve, and location of ganglia of the hindgut?

A
  • S2-S4
  • pelvic splanchnic nerves
  • organ walls
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14
Q

What is analogous to the urachus?

A

-median umbilical ligament

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15
Q

What is an esophageal stenosis or atresia?

A
  • narrowed or occluded esophagus due to incomplete recanalization, usually found in the lower 1/3
  • may also be caused by vascular abnormalities or comprised blood flow
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16
Q

What is an esophageal replacement?

A
  • typically done for congenital esophageal atresia or acquired caustic strictures (scarring from acid or lye)
  • successful anastomoses may be performed in those with long gap esophageal atresia (>3cm between the proximal and distal esophageal remnants)
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17
Q

What is a colon interposition?

A

-a section of colon is taken from its normal position in the gut and transposed with blood supply in tact into the chest where it is joined to the esophagus

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18
Q

What is a gastric tube esophagoplasty?

A

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

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19
Q

What is a gastric transposition?

A

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

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20
Q

What does a normal stomach have to keep stomach acid from leaving the stomach?

A

-a sphincter

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21
Q

What is esophagitis?

A

Inflammation caused by acid in stomach

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22
Q

What is Barrett’s esophagus?

A

Acid backing up from stomach changes esophagus lining

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23
Q

What is a hiatal hernia?

A

-stomach bulging above the diaphragm

24
Q

How does the. Stomach develop?

A
  • dilation of the foregut
  • dorsal surface grows relatively faster than ventral surface
  • suspended by dorsal and ventral mesentery
  • dorsal side of the tube grows rapidly, expands and there is a simultaneous clockwise rotation of 90 degrees
25
Q

How does the stomach rotate?

A
  • left side of the stomach now lies anterior and the right side posterior
  • the left vagus becomes the anterior vagal trunk and the right vagus the posterior vagal trunk
26
Q

What is hypertrophic pyloric stenosis?

A
  • usually present 2-3 weeks after birth
  • pyloric sphincter is too large to allow food through
  • projectile vomiting with no bile
27
Q

How does. The duodenum. Develop?

A
  • proliferation of epithelium
  • recanalization of lumen
  • defective vacuolization
28
Q

Where do duodenal stenoses typically occur?

A

-3rd or 4th part

29
Q

Where do duodenal atresias occur?

A
  • 2nd or 3rd part
  • 1/4 have Down’s
  • autosomal recessive
30
Q

What is a duodenal cyst?

A

-a tubular structure with an internal lining of GI epithelium, smooth muscle in its wall and adherence to some portion of the alimentary canal

31
Q

Where and how do the liver and gallbladder develop?

A
  • ventral mesentery
  • hepatic cords coalesce around extraembryonic veins to form sinusoids
  • bile ducts form
  • gallbladder and cystic duct are outgrowths of the bile duct
32
Q

What does the growth of the liver divide the ventral mesentery into?

A

-falciform ligament and lesser omentum

33
Q

What does the ductus venosus form in the adult?

A

Left umbilical vein

34
Q

What does he ligamentum venosum derive from?

A

-ductus venosus

35
Q

What is a extra hepatic biliary atresia?

A
  • incomplete canalizations of the bile duct
  • jaundice: high levels of bilirubin in bloodstream
  • dark urine: bilirubin filtered by kidney and excreted in urine
  • pale stool: no bile or bilirubin is being emptied into the intestine

-surgical correction or transplant

36
Q

What regulates pancreas development?

A

-PDX1 -> pancreas and duodenum
+paired homeboy genes specify endocrine cell lineages
-PAX4: cells secreting insulin, somatostatin and pancreatic polypeptide
-PAX6: cells secreting glucagon
-islets of Langerhans appear in 3rd fetal month
-insulin secreted by 5th month

37
Q

What is the biliary system?

A

-gallbladder and cystic duct

38
Q

How does the biliary system develop?

A
  • tubular structure (pars cystica) arising from elongation and molding of the caudal portion of the hepatic diverticulum
  • dorsal and ventral pancreas fuse after clockwise rotation of the ventral bud around the caudal part of the foregut
39
Q

How is the pancreas drained?

A
  • drained through the ventral pancreatic duct, which joins the common bile duct at the level of the major papilla
  • dorsal pancreatic duct empties into the common bile duct at the minor papilla
  • heptoduodenal-pancreatic common duct comprises the duct shared between the liver and the ventral pancreas
  • main pancreatic duct derives from the merger of the dorsal and ventral pancreatic ducts
40
Q

What is an annular pancreas?

A
  • ventral and dorsal pancreatic buds form a ring around the duodenum
  • presents as duodenal obstruction
41
Q

What is accessory or ectopic pancreatic tissue?

A
  • can be found from distal esophagus through the primary intestinal loop(distal transverse)
  • most common in stomach or ileum
42
Q

Caudal to the duodenum what is a probable cause of atresias or stenoses?

A

-vascular compromise

43
Q

How is the midgut rotated and fixed?

A
  • rapid growth of the midgut starts at week 6
  • produces normal herniation
  • gut loops into the umbilical cord
  • as this happens, the loop rotates 90 degrees counterclockwise around the superior mesenteric
  • 10 weeks: the herniated loops return to the abdominal cavity and rotate an additional 18- degrees
44
Q

What is malrotation of the midgut?

A
  • partial rotation only
  • abnormally positioned viscera
  • increased risk of entrapment of portions of the intestine
  • usually presents within 1st week as duodenal obstruction with bilious vomiting
  • infants: recurrent abdominal pain, intestinal obstruction, malabsorption/diarrhea, septic shock, solid food intolerance, common bile duct obstruction, abdominal distension, adn failure to thrive
45
Q

What is volvulus?

A
  • abnormal twisting of the intestine causing obstruction
  • compromises the intestine or the blood flow
  • bloat: any deep chested, large breed dog is at risk for bloat
46
Q

What is bilious emesis?

A
  • green colored bile
  • malrotation with volvulus was diagnosed an the infant underwent emergent surgical correction
  • NOT normal
47
Q

What is an omphalocele?

A
  • herniation of abdominal contents through enlarged umbilical ring
  • normal if it is temporary
  • the gut should return into the abdomen as the embryo grows
  • midgut loop fails to return to abdominal cavity
  • pale, shiny sac protrudes from base of umbilical cord
  • associated with high mortality rate and other severe malformations (neural tube, cardiac, and chromosomal)
48
Q

What is gastroschisis?

A
  • failure of anterior abdominal wall musculature to close during folding
  • gut contents not surrounded by membrane
  • frequency increasing in young women
  • possibly associated with cocaine use
  • not associated with chromosomal abnormalities or other malformations
  • survival rate is excellent
49
Q

What is a ileal diverticulum/MEckel’s diverticulum?

A
  • remnant of vitelline duct, failure to close
  • asymptomatic
  • gastric or pancreatic tissue may be in it
  • fistula present
  • fecal discharge through umbilicus
  • 2% prevalence, 2 ft proximal to the ileocecal valve in adults
  • half of those who are symptomatic are younger than 2 yrs of age
50
Q

What invades the hindgut?

A

-neural crest cells and gives rise to majority of enteric nervous system in entire system

51
Q

What is Hirschsprung’s disease?

A
  • congenital aganglionic megacolon, is a motor disorder of the colon that causes a functional intestinal obstruction
  • both plexuses are affected
  • more prevalent in males
  • pathogenesis of the disease is failure of migration of the NCCs that form the colonic ganglion cells
  • without parasympathetic innervation the colon can’t relax or undergo peristalsis resulting in functional obstruction
52
Q

What parts of gut is affects by HD?

A
  • affect more cranial parts of the gut tube
  • 70-80% descending and sigmoid colon
  • 1-20% transverse colon
  • 3% entire colon
  • decreased occurrence in more proximal parts bc these are associated with higher mortality rate
53
Q

How do you fix HD?

A
  • surgery
  • procedure is called pull-through surgery and involves removing the section of the colon that has no ganglia cells, then reconnecting the remaining healthy end of the colon to he rectum
54
Q

What is the difference between primary and secondary retroperitoneal?

A

Primary: any organ that developed outside the abdominal cavity which never had a mesentery to begin with

Secondary: portions of the gut tube whose mesentery has fused with the lining peritoneum

Intraperitoneal: organs with mesentery

55
Q

Ow is. Regional specification of the gut tube done?

A

-lateral folding brining the 2 sides together

Anatomy II Exam I (7 decks)

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