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A. White- Human Anatomy > Embryology Of The Gastrointestinal System > Flashcards

Embryology Of The Gastrointestinal System Flashcards

1
Q

What part of the gut tube is encoded by SOX2?

A

Esophagus

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2
Q

What part of the gut tube is encoded by PDX1?

A

Duodenum and pancreas

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3
Q

What part of the gut tube is encoded by CDXC?

A

Small intestine

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4
Q

What part of the gut tube is encoded by CDXA?

A

Large intestine

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5
Q

Specificiation in the gut tube is initiated by an RA gradient that causes transcription factors to be expressed in different regions of the tube. What is also required in the gut tube?

A

An interaction between the epithelium (endoderm) and mesenchyme (splanchnic mesoderm) initiated by SHH.

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6
Q

In addition to regionalization, development of the gut tube also involves:

A

Continuous elongation

Herniation past the body wall (into the umbilical cord)

Rotation and folding for efficient packing

Histiogenesis and further maturation of the epithelial lining.

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7
Q

What is the 2 layered fold of peritoneum that the gut tube becomes suspended by?

A

Dorsal mesenteries

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8
Q

What are mesenteries?

A

Reflections of parietal peritoneum onto the gut tube.

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9
Q

How many segments is the gut tube divided into?

A

3.

Foregut, midgut and hindgut.

Innervation and blood suplpy to these segments is strongly patterned.

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10
Q

What organs are found in the foregut?

A

Esophagus

Stomach and 1/2 duodenum

Liver

Gall bladder

Pancreas

Spleen

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11
Q

What organs are found in the midgut?

A

1/2 duodenum

Jejunum

Ileum

Cecum and appendix

Ascending colon

2/3 transverse colon

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12
Q

What organs are found in the hindgut?

A

1/3 transverse colon

Descending colon

Sigmoid colon

Rectum

Upper part of the anal canal

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13
Q

What artery supplies the foregut?

A

Celiac artery

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14
Q

What vessel supplies the midgut?

A

Superior mesenteric artery

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15
Q

What artery supplies the hindgut?

A

Inferior mesenteric artery.

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16
Q

What preganglionic cell bodies (and nerve) supply the foregut?

A

T5 - T9

Greater splanchnic nerve

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17
Q

What preganglionic cell bodies (and nerve) supply the midgut?

A

T9 - T12

Lesser splanchnic nerve

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18
Q

What preganglionic cell bodies (and nerve) supply the hindgut?

A

T12 - L2

Least splanchnic nerve

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19
Q

The least splanchnic nerve goes to what plexus?

A

Aortico-renal plexus

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20
Q

What plexus do the lumbar splanchnics from L1 and L2 go to?

A

Inferior mesenteric plexus

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21
Q

What is the parasympathetic innervation of the forgut and midgut?

A

Vagus nerve

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22
Q

What is the parasympathetic innervation of the hindgut?

A

Pelvic splanchnic nerve

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23
Q

What are preganglionic cell bodies found in the foregut and midgut?

A

Brainstem

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24
Q

Where are preganglionic cell bodies of the hindgut found?

A

S2 - S4

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25
Q

Where are the location of ganglia in the forgut, midgut and hindgut?

A

Organ walls.

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26
Q

Where is a narrowed or occluded esophagus due to incomplete recnalization (esophageal atresia) found?

A

In the lower 1/3 of the esophagus.

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27
Q

Esophageal atresia can be caused by incomplete recanalization. What can it also be caused by?

A

Vascular abnormalities or compromixed blood flow.

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28
Q

What is colon interposition?

A

A type of esophageal replacement in which a section of a colon is taken from its normal position in the gut, and transposed to the chest. It is then joined to the esophagus above and stomach below.

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29
Q

What is a gastric tube esophagoplasty?

A

A longitudinal segmentis taken from the stomach, which is then swung up into the chest and joined into the esophagus.

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30
Q

What is a gastric transposition?

A

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

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31
Q

What is a congenital esophageal hernia?

A

A hernia of the esophagus.

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32
Q

True or false: the stomach has attachments to both dorsal and ventral mesenteries.

A

True.

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33
Q

How do the esophagus and stomach change as it develops?

A

They start as a straight tube suspended by dorsal and ventral mesentary.

The dorsal side of the tube grows rapidly, expands that there is a simultaneous clockwis rotation of 90 degrees.

34
Q

The left side of the stomach lies anterior and the right side posterior.

A

Therefore, the left vagus becomes the anterior vagal trunk and the right vaus the posterior vagal trunk.

35
Q

What are symptoms of hypertrophic pyloric stenosis?

A

Projectile vomiting/no bile.

36
Q

You encounter a patient who is 25 weeks pregnant. An ultrasound of the fetus reveals that there is gas distended int he stomach and duodenum. After birth, surgery may reveal that the infant has what?

A

A duodenal atresia.

37
Q

What is a duplication cyst?

A

A tubular structure with an internal lining of gastrointestinal epithelium, smooth muscle in its wall and adherence to some portion of the alimentary tract.

38
Q

Where does the liver develop?

A

In the ventral mesentery.

39
Q

The liver develops in the ventral mesentery. What also develops in the venral mesentery?

A

Gallbladder and bile ducts.

40
Q

Hepatic cords coalesce around extraembryoinic veins to form what structure?

A

Sinusoids.

41
Q

What are the gallbladder and cystic duct outgrowths of?

A

The bile duct.

42
Q

What does the growth of the liver divide?

A

Growth of the liver divides the ventral mesentery into falciform ligament and lesser omentum.

43
Q

What is the ligamentum venosum?

A

A fibrous remnant of the ductus venosus.

44
Q

What is an extrahepatic biliary atresia?

A

An incomplete canalization of the bile duct.

Symptoms include jaundice, dark urine and pale stool (no bile or bilirubin is being emptied into the intestine).

Treatment is surgical correction or a transplant.

45
Q

What gene encodes for the pancreas and duodenum?

A

PDX1

46
Q

What does the gene PAX 4 encode?

A

Cells secreting insulin, somatistatin and pancreatic polypeptide.

47
Q

What does the gene PAX 6 encode?

A

Cell secreting glucagon.

48
Q

When do Islets of Langerhans appear?

A

In the third fetal month

49
Q

When does insulin secretion occur?

A

In the fifth month.

50
Q

What does the biliary system (gallbladder and cystic duct) initially develop from?

A

A tubular structure that arises from elongation and molding of the caudal portion of the hepatic diverticulum.

51
Q

When do the dorsal and ventral pancreas fuse?

A

After clockwise rotation of the ventral bud around the caudal part of the foregut.

52
Q

What is the pancreas predominantly drained through?

A

The ventral pancreatic duct, which joins the common bile duct at the level of the major papilla.

53
Q

What does the dorsal pancreatic duct empty into?

A

The common bile duct at the level of the minor opapilla.

54
Q

What duct comprises the duct sharted between the liver and the ventral pancreas?

A

The hepato-pancreatic common duct.

55
Q

What does the main pancreatic duct derive from?

A

The merger of the dorsal and ventral pancreatic ducts.

56
Q

How can the pancreas be a duodenal obstruction?

A

When ventral and dorsal pancreatic buds form a ring around the duodenum.

57
Q

Where can accessory or ectopic pancreatic tissue be found?

A

From the distal esophagus through the primary intestinal loop.

It is most common in the stomach or ileum.

58
Q

What are the derivatives of the midgut?

A

Duodenum distal to entrance of bile duct.

Free small intestine (jejunum, ileum)

Cecum and appendix

Ascending colon

Right 2/3 or transverse colon

Superior mesenterc artery.

59
Q

Where do gut atresias and stenoses occur?

A

Anywhere along the intestine.

If they are in the upper duodenum, it is usually due to a failure to recanalize.

If they are caudal to the duodenum, these are probably due to vascular compromise.

60
Q

When does rapid growth of the midgut start?

A

About 6 weeks.

61
Q

As the gut loops into the umbilical cord, how does it rotate?

A

The loop rotates 90 degrees counterclockwise around the superior mesenteric artery.

62
Q

When does the herniated loop of the midgut return to the abdominal cavity?

A

About the 10th week.

It rotates an additional 180 degrees (270 total).

63
Q

What can occur if the midgut does not rotate fully?

A

There is an increased risk of entrapment of portions of the intestine.

It usually presents within the first week as a duodenal obstruction with bilious vomiting.

64
Q

What is a volvulus?

A

Abnormal twisting of the intestine that causes an obstruction.

It compromises the intestine or the blood flow.

65
Q

What is situs inversus caused by?

A

Bowel maltoration.

66
Q

What are two examples of body wall defects?

A

Omphalocele

Gastroschisis

67
Q

What is omphalocele?

A

A herniation of abdominal contents through an enlarged umbilical ring.

It is usually tmeporary and the gut returns into the abdomen as the embryo grows.

68
Q

What is gastroschisis?

A

A failure of the anterior abdominal wall musculature to close during folding.

Gut contents are NOT surrounded by a membrane use.

It is not associated with chromosomal abnormalities or other malformations.

69
Q

What is an ileal diverticulum a remnant of?

A

A vitelline duct.

70
Q

What is the ileal diverticulum a result of?

A

A failure of the vitelline duct to close.

71
Q

How are enteric neurons organized?

A

In ganglia found within two main plexi.

An outer myenteric plexus develops first and occupries a position between the longitudinal and circular muscle layers.

An inner submucosal plexus forms later in gestation and resides within the submucosa.

72
Q

What causes Hirschsprung’s disease?

A

A failure of migration of the neural crest cells that form the colonic ganglion cells.

73
Q

What is Hirschsprung’s disease?

A

A congential aganglionic megacolon. It is a motor disorder of the colon that causes a functional intestinal obstruction.

74
Q

What functions of the colon are lost without parasympathetic innervation?

A

The colon cannot relax or under peristalsis, resulting in a functional obstruction.

75
Q

Where is Hirschsprung’s disease most commonly found?

A

In the descending a sigmoid colon.

There is a decreased occurrence in the more proximal parts because these are associated with higher mortality rate and/or increased incidence of multiple congenital abnormalities.

76
Q

What is the treatment for Hirschsprung’s disease?

A

Surgery.

It involves removing the section of the colon that has no ganglia cells, then connecting the remaining healthy end of the colon to the rectum.

77
Q

How does rotation affect the peritoneal cavities?

A

It changes their size.

Their anatomical relationship of the organs to one another will also change.

Changes will also be found in the dorsal mesenteries. Structures will be primarily or secondarily retroperitoneal.

78
Q

What is a primarily retroperitoneal organ?

A

Any organ that developed outside the abdominal cavity which never had a mesentery to begin with.

79
Q

What is a secondarily retroperitoneal organ?

A

Portions of the gut tube whose mesentery has fused with the lining peritoneum.

80
Q

What are intraperitoneal organs?

A

Organs with a mesentery.

81
Q

During rotation and herization of the gut, some parts become pushed back, and become ____.

A

Secondarily retroperitoneal.

82
Q

How is the specification of the gut tube controlled?

A

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

A. White- Human Anatomy (23 decks)

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