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GI Midterm > Embryology of the GI > Flashcards

Embryology of the GI Flashcards

1
Q

Specification of the gut tube is initiated by _ _ gradient that causes transcription factors to be expressed in different regions of the tube.

A

retinoic Acid

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2
Q

What molecular regulator initiates the interaction between the eithelium and mesenchyme (splanchnic mesoderm) in the development of the gut tube?

A

SHH

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3
Q

what layers of the gut tube is derived from splanchnic mesoderm?

A

LP, Submucosa, muscularis externa and seroa/adventia.

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4
Q

Where are the preganglionic cell bodies arise from for the foregut, midgut, and hindgut?

A 
Foregut = T5-T9 (greater splanchnic N)
Midgut = T9-T12 (lesser splanchnic N)
Hindgut = T12-L2  (least splanchnic N)
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5
Q

what are the preaortic ganglion associated with the foregut, midgut, and hindgut?

A 
Foregut = celiac ganglion
midgut = superior mesenteric ganglion
Hindgut = inferior  mesenteric ganglion
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6
Q

where does the esophagus develop from?

A

Lung bud as a laryngotracheal diverticulum

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7
Q

What separates the primitive esophagus from the trachea?

A

Tracheoesophgeal septum

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8
Q

what is the most common congenital abnormality associated with the esophagus where the upper segment of the esophagus ends in a blind pouch and the lower part originating from the trachea just above bifurcation.

A

Tracheoesophageal fistula with esophageal atresia

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9
Q

What is esophageal stenosis or atresia and what can cause it?

A

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

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10
Q

How are congenital esophageal atresia treated?

A

Those with few inches of gap can be corrected surgically where they cut out the occluded parts and reconnect the rest. In atresia greater then 3 cm, will require esophageal replacement or other other lengthening techniques.

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11
Q

Colon interposition is a technique used for what?

A

it’s used for esophageal replacement - a section of the colon is taken from it’s normal position with it’s blood supply and transposed into the chest where it is joined to the esophagus above and stomach below

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12
Q

What is gastric tube esophagoplasty used for?

A

It’s a longitudinal segment taken from the stomach, which is then swung up into the chest and joined to the esophagus to correct esophageal atresia.

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13
Q

Describe gastric transposition as a means for correcting esophageal atresia.

A

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

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14
Q

What is a Zenker’s Diverticulum?

A

It’s a pocket looking thing that forms out of the eosphageal wall and food and fluid can accumulate in their.

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15
Q

How is the stomach formed?

A

It’s formed as a dilation of the foregut.

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16
Q

Describe the development of the stomach?

A

It starts out as a dilation of the foregut connecting the esophagus in a straight vertical tube suspended by dorsal and ventral mesentery. the left side (dorsal) grows rapidly, expands and there is a simultaneous clockwise roataion of 90 degrees. this rotation moves the left side of the stomach more anterior and right side more posterior.

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17
Q

Describe how the left and right vagal trunk become anterior and posterior.

A

During the development of the stomach, the stomach rotates which puts the inital left side of the stomach more anterior and right side of the stomach more posterior. The

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18
Q

What is hypertrophic pyloric stenosis?

A

overgrowth of the pyloric sphicter such that contacts from the stomach cannot pass into the duodenum. Babies will present with projectile vomitting with No bile in the vomit indicating that the contents did not move to the duodenum. babies will also present with Scaphoid abdomen and/or a olive sized mass on that can be felt which is the overgrown pyloric sphincter.

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19
Q

When does hypertorphic pyloric stenosis usually present?

A

2-3 weeks after birth

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20
Q

where is a common sites of duodenal stenosis?

A

3rd and 4th.

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21
Q

Where is a common site of duodenal atresia?

A

2nd and 3rd parts.

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22
Q

A new born presents with double bubble sign. What is wrong with the baby?

A

Duodenal atresia. There’s air in the stomach and there’s air in the duodenum past the atresion.

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23
Q

Why is duodenal duplication cysts a big deal?

A

Cysts are tubular structure with an inernal lining of gastrointestinal epithelium, smooth muscle in its wall an adheres to some portion of the alimentary tract. If the cyst is to burst or if it was to be get so big that ti perforates parts of the alimentary tract, this can introduce meconium into the peritoneum and cause peritonitis and ascites.

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24
Q

in embyronic devleopment of the gut tube, what diverticulas grow out of the ventral mesentery?

A
  1. Pancreatic diverticulum (from both ventral and dorsal)
  2. Cystic diverticulum
  3. hepatic diverticulum.
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25
Q

all foregut endoderm has the potential to express liver-specific genes and to differentiates into liver tissue. But we don’t see livers all over. What signals the liver to develop where it does?

A

Foregut endoderm expression to become liver is blocked by unknown signals from the trunk mesoderm and ectoderm, possibly by Wnts and restricts the location of liver to develop in the posterior endoderm. In the inhibitory factors not to bcome a liver is blocked in the area of the liver by FGF2 which is sected by the cardiac mesoderm and BMPs secrted by the septum transversum.

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26
Q

What instructs the gut endoderm to express liver specific genes?

A

Cardiac mesoderm and septum transversum.

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27
Q

Development of what organ divides the ventral mesentery?

A

The liver.

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28
Q

After the liver is development the ventral mesentery is divided into what?

A

falciform filament and lesser omentum.

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29
Q

What is the round ligament (ligamentum teres hepatis) of the liver?

A

it is a remnant of embryonic umbilical vein.

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30
Q

How does Extrahepatic biliary atresia present?

A

Juandice - 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

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31
Q

What is Menkes Disease ?

A

Aka kinky hair syndrome . decrease in the cell’s ability to absorb copper.

32
Q

Kayser- Fleischer ring is seen with what disease state and what is the cause of it?

A

Seen in Wilson’s disease where copper is not eliminated by the liver and instead accumulates around the iris of the eye.

33
Q

What part of the pancreas comes from the ventralpancreatic bud?

A

The uncinate process of the head comes from the ventral pancreatic bud

34
Q

The head, body, and tail of the pancreas is derived from which pancreatic bud?

A

DOrsal pancreatic bud

35
Q

The pancreas develops as two buds, and at some point in development they fuse, what is a common congentital problem that can arise from errors in the fusion of the two buds?

A

Annular pancreas where the pancreas wraps around the duodenum which can cuase obstruction.

36
Q

How can you distinguish the annular pancreas from a hypertorphic pyloric sphincter?

A

The vomit seen with annular pancreas will be billious and there would not be a palpable knot in the epigastric region.

37
Q

What molecular regulator is involved in the pancreas and duodenum?

A

PDX1

38
Q

What molecular regulator for the cells secreting insulin, somatostatin and pancreatic polypeptide?

A

PAX4

39
Q

What is the molecular reglator for cells secreting glucagon?

A

PAX6

40
Q

By what month in development does the fetus start to secrete insulin?

A

5th month.

41
Q

What is the most common site for ectopic pancreas?

A

Stomach or the ileum (Meckel’s diverticulum)

42
Q

During rotation of the foregut which peritoneal cavity gets smaller?

A

The right side because of the liver.

43
Q

Which part of the duodenum is considered part of the foregut?

A

The proximal or upper duodenum which arises from the caudalmost part of the foregut and is served by anterior and posterior branches of the superior pancreaticoduodenal artery - branch of the celiac artery.

44
Q

Which structure of the foregut becomes secondarily retroperitoneal?

A

The upper duodenum and pancreas due to the rotation of the gut tube, the duodenum and pancreas are pushed up against the body wall.

45
Q

Gut atresias and stenoses can occur at any point, but the reason for the upper duodenum is usualy due to failure to 1, and the cadual to the duodenum is usually due to 2.

A
  1. failure to reanalize

2. vascular compromise.

46
Q

What is apple peel atresia and where does it usualy occur?

A

It’s usually at proximal jejunum and the intestine is short and portion distal to the defect is coiled around mesenteric remnant like an apple peel.

47
Q

At around what week of development does the midgut start to grow rapidly?

A

Week 6

48
Q

The midgut loops into the umbilical cord and as this happens, it rotates 90 degrees CCW around what structure?

A

Superior mesenteric a.

49
Q

At what weeks does the herniated loops of the gut return back to the abdominal cavity?

A

week 10

50
Q

How many total degrees does the gut loops rotate?

A

270

51
Q

Around what week and how would a malrotation of the viscera present?

A

Usually presents at week 1 with bilious vomitting due to duodenal obstruction.

52
Q

with malrotation of the gut, how do infants present?

A

recurrent abd pain, intestinal obsstuction, malapsorption/diarrhea, peritonitis/septic shock, solid food intolerance, common bile duct obstruction, abdominal distention, and faulto thrive.

53
Q

What is Volvulus?

A

It’s a subtype of malrotation in which a loop of bowel is twisted about a focal point along the mesentery attached to the intestinal tract that may result in a bowel obstruction.

54
Q

How do volvulus usually present?

A
  1. Bowel obsturction manifested as abdominal distension and bilious vomitting
  2. Ischemia to the affected portion of intestine.
55
Q

What is intussusception?

A

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

56
Q

Ileum telescopes inside ascending colon, obsttucting passage of intestinal content which can cause bleeding and you may seen currant jelly stools. Blood vessels become trapped between layers; blood flow decreases leading to edema and strangulation of bowel which will cause gangrene, sepsis, shock and often death if not corrected. What abnormalitty is described above?

A

Intussusception

57
Q

Malrotation can often cause situs inversus. What is situs inversus?

A

It’s a congential condition in which the major vsceral organs are reversed or mirrored from their normal arrangment of internal organs.

58
Q

If you see Ladd’s band on a CT, what congential conditional is that due to?

A

Situs inversus abdominus and malrotation.

59
Q

What are some common body wall defects?

A

Omphalocele
gastroschisis
prune belly syndrome

60
Q

Omphalocele is deemed normal if it is temporary, what makes it a congential abnormality?

A

Omphalocele is the herniation of abdoinal contents through the enlarged umbilical ring. It’s normal during develoment since the growing gut herniates intot he umbilicus but it returns back to the gut as the embryo grows. Omphalocele becomes a problem when the midgut loop fails to return to abdominal cavity, and a pale, shiny sac protrudes from base of the umbilical cord.

61
Q

What is the cause of gastroschisis?

A

Failure of anteior abdominal wall musculature to close during folding and so the gut contents are not surrounded by a membrane.

62
Q

Gastroschisis is not usually associated with chromosomal abnormalities, but rather extriinsic factors like _?

A

creational drug use, like cocaine.

63
Q

What is Eagle Barrett syndrome?

A

Aka Prune Belly syndrome. Presents as a traid: 1. anterior abdominal wall: musculature is deficient or absent. 2. urinary tract anomalies (mega-ureters, large baldder). 3. Bilateral cryptorchidism.

64
Q

What are the two 2 hypotheses that explains the etiology of PBS?

A
  1. Urinary tract obstruction - hypoplastic or dysplatic prostate creates a urinary traction obsturction leading to overdistension of the bladder and the upper urinary tract which stretches the abdominal wall and cause damage to the abdominal musculature and interferes with the descend of the testicles.
  2. Primary mesodermal developmental defect. - an insult between 6 to 10 weeks of gestation which disrupts the development of the intermediate and lateral plate mesoderm which give rise to both the abdominal wall (lateral plate mesoderm) and genitourinary tract including the prostate (IM)
65
Q

What is the vitelline duct?

A

Aka omphalomesenteric duct. It is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus. Appears around week 4 and disappears at around week 9.

66
Q

What is the Meckel’s diverticulum?

A

It’s a true congenital diverticulum which is a bulge in the small intestine which is a vestigial remnant of the omphalomesenteric duct (vitteline duct).

67
Q

Explain the rules of 2 in describing the ileal diverticulum.

A

2% prevalence
2:1 female predominance?
Location is 2 feet proximal to the ileocecal valie in adults, and half of those who are symptomatic are younger than 2 years of age.

68
Q

How would you distinquish a urachal fistual from a meckel’s fistual?

A

By asking if you see feces or urine through the fistual. In Meckel you’ll see feces coming out of the umbilicus. in urachal you’ll see urine.

69
Q

What is Hirshsprung’s Disease?

A

It’s a congenital aganglionic megacolon. It’s a motor disorder of the colon that causes a functional intestianl abstruction. both the myenteric and submucosal.

70
Q

What is the cause of hirshsprung’s disease?

A

It’s the failure of the neural crest cells to migrate to from the colinic ganglion cells.

71
Q

Which part of the colon does hirshsprung disease mainly affect?

A

Sigmoid Colon

72
Q

Occurance of Hirshprung disease in the proxmal parts of the intestine is rare becuase _?

A

Proximal parts are associated with higher mortality rate and or increased incidence of multiple congential abnormalities.

73
Q

Pull-through surgery is performed as a treatment for Hirshsprung disease? What does pull-through surgery involve?

A

It involves removing parts of the colon that has no ganglia cells and then connecting the remaining healthy ends of the colon to the rectum.

74
Q

What midgut organs are retroperitoneal?

A

Ascending colon, descending colon, duodenum and pancreas

75
Q

The cloaca is divided by 1 into 2 and 3.

A
  1. urorectal septum
  2. Urogenital sinus
  3. rectum
76
Q

which enteric neural plexus develops first and where?

A

Myenteric plexus develops first and occupies a position between the longitudinal and circular muscle layers.

GI Midterm (11 decks)

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