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Semester 3 - Gastrointestinal > 5. Development of the GI Part 2 > Flashcards

5. Development of the GI Part 2 Flashcards

1
Q

What does the midgut give rise to?

A
  • Small intestine, including most of duodenum
  • Caecum & appendix
  • Ascending colon
  • Proximal 2/3 transverse colon
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2
Q

What is the first thing to happen to the midgut when it elongates enormously and runs out space?

A

It loops forming the primary intestinal loop

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3
Q

What connects the primary intestinal loop to the yolk sac?

A

Vitelline duct

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4
Q

What does the part of the midgut that is connected to the yolk sac by the duct develop into?

A

Ileum

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5
Q

What forms the axis of the primary intestinal loop and what is the midgut above and below the axis called?

A

Superior mesenteric artery. Cranial and caudal limbs

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6
Q

Why does physical herniation of the midgut occur?

A

Liver grows rapidly along with the primary intestinal loop, abdominal cavity too small to accommodate both

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7
Q

Where does the intestine herniate into in physiological herniation and what week does it occur?

A

Umbilical cord. 6th week

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8
Q

what does the carnial part become?

A

small intestine

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9
Q

what does the caudal part become?

A

large intestine

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10
Q

describe the Midgut rotation in steps

A

• There is a cranial limb and a caudal limb with an axis comprising the Superior Mesenteric Artery
• This group go through a series of counter clockwise 90 degree rotations (if viewed from the
front.
• The result of this is the caudal derivatives end up lying to the right of the cranial derivatives and the transverse colon being on top of the duodenum

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11
Q

What does the midgut rotate around?

A

superior mesenteric artery

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12
Q

What happens in the first rotation of the midgut?

A

Cranial limb moves to the right of the SMA, caudal limb moves to the left. Small intestine begins to develop, and herniates into the umblical cord.

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13
Q

What happens in the second rotation of the midgut?

A

Cranial limb moves below SMA, and caudal limb above. Caecal swelling develops from the caudal limb. Transverse colon begins to move in front of duodenum

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14
Q

What happens in the third rotation of the midgut?

A

Cranial limb moves to the left of SMA, and caudal limb to the right. Caecum remain at the sub-hepatic region.

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15
Q

At what stage in the rotation of the midgut does it return into the abdominal cavity and which part reenters first?

A

Returns during the third rotation(10th week), cranial limb enters first and moves to left side. (presence of caecal swelling stops it from entering)

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16
Q

What happens after the third rotation of the midgut?

A

Elongation of the ascending colon and decent of the caecal bud

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17
Q

what are midgut rotational problems?

A

Malrotation

Reversed rotation

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18
Q

describe malrotation

A

• Incomplete rotation
• Midgut loop makes only one 90° rotation
Left-sided colon

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19
Q

describe reversed rotation

A
  • Midgut loop makes one 90° rotation clockwise

* Transverse colon passes posterior to the duodenum

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20
Q

What is the main risk associated with midgut defects?

A

Volvulus

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21
Q

What is a volvulus?

A

twisting of the bowel

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22
Q

What can happen to a volvulus?

A

Can become strangulated and ischaemic

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23
Q

What are 3 abnormalities resulting from persistence of the vitelline duct?

A

Vitelline cyst, vitelline fistula, Meckel’s diverticulum

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24
Q

How does a vitelline cyst develop?

A

midportion of the vitelline duct remains patent and each end is obliterated, and mucus then accumulates within the cyst

25
Q

What is a vitelline fistula?

A

Failure of the Vitelline duct to obliterate, direct communication between the umbilicus and intestinal tract.

26
Q

What would you expect to see on a vitelline fistula?

A

contents of the intestinal tract coming out of the umbilicus.

27
Q

What is Meckel’s diverticulum?

A

Small bulge due to out pouching of the small intestine due to failure of the vitelline duct to completely obliterate.

28
Q

What is the most common GI congenital abnormality?

A

Vitelline diverticulum

29
Q

What is the rule of 2’s for a Meckel’s diverticulum?

A

2% population, 2 feet from ileocaecal valve, detected in under 2’s, 2:1 ratio males:females

30
Q

What might a Meckel’s diverticulum contain?

A

Ectopic gastric or pancreatic tissue, intestines are not adapted for gastric secretions

31
Q

What can happen to the lumen of the gut due to its rapid growth?

A

Many become partly or completed obliterated.

32
Q

Which parts of the gut lumen may become obliterated due to rapid growth?

A

Oesophagus, small intestine, bile duct

33
Q

What is the process of restoring the lumen in the gut tube where it has been obliterated?

A

Recanalisation

34
Q

What can occur if recanalisation is unsuccessful?

A

Fully unsuccessful = atresia (Lumen obliterated),

partly = stenosis (Lumen narrowed)

35
Q

What is pyloric stenosis and what is a characteristic sign of this in babies?

A

o hypertrophy of the circular muscle in the region of the pyloric sphincter
o NOT a recanalisation failure
o Common abnormality of the stomach in infants
o narrowing of the exit from the stomach causes characteristic projectile vomiting

36
Q

where does atresia/stenosis commonly occur?

A

duodenum

37
Q

What is gastroschisis?

A

Defect of ventral abdominal wall, failure of the wall to close during embryonic folding. Resulting in extrusion of gut tube through abdominal wall. Not covered in peritoneum.

38
Q

What is the gut tube exposed to in gastroschisis?

A

Aminotic fluid as it is not covered in peritoneum, which can damage the gut.

39
Q

What is the prognosis of gastroschisis?

A

90-95% survival rate, depending on how much of the gut is on the outside

40
Q

What is omphalocele?

A

Persistence of physiological herniation, covered in peritoneum - midgut herniation fails to return to abdominal cavity

41
Q

What is omphalocele often associated with?

A

With other genetic conditions (often trisomies)

42
Q

why is omphalocele mortality higher than gastroschisis?

A

omphalocele associated with other developmental abnormalities

43
Q

what are the two Anterior abdominal wall defects

A

gastroschisis

omphalocele

44
Q

What does the hindgut give rise to?

A
  • Distal 1/3 transverse colon
  • Descending colon
  • Rectum
  • Superior part of anal canal
  • Epithelium of urinary bladder
45
Q

What separates the anal canal into its histological superior and inferior parts?

A

Pectinate line.

46
Q

What germ layer is responsible for development of the superior and inferior parts of the anal canal?

A

Superior = endoderm, inferior = ectoderm

47
Q

What is the arterial supply to the superior and inferior anal canal?

A

Superior = IMA, Inferior = Pudendal A

48
Q

What is the nerve supply to the superior and inferior anal canal?

A

Superior = S2-4 pelvic parasympathetics, Inferior = S2-4 Pudendal Nerve

49
Q

What is the lymphatic drainage of the superior and inferior anal canal?

A

Superior = deep internal iliac nodes, Inferior = Superficial inguinal nodes

50
Q

What is the epithelial lining of the superior and inferior anal canal?

A

Superior = columnar epithelium, Inferior = stratified squamous

51
Q

What is the consequence of two embryonic tissues to the anal canal

A
  • above the pectinate line the only sensation possible is stretch, vague pain
  • while below the pectinate line the tissue is temperature, touch and pain sensitive, localised pain
52
Q

Where does visceral pain from foregut, midgut and handgut localise to?

A

Epigastric area, periubilical area and suprapubic

53
Q

What are 3 congenital abnormalities of the anal canal?

A

Imperforate anus, anal/anorectal genesis, hindgut fistulae (e.g urorectal fistula)

54
Q

What is imperforate anus?

A

Failure of anal membrane to rupture, anal opening not present.

55
Q

what divides the cloaca and into what?

A

urorectal septum divides the cloaca into urogenital sinus and anorectal canal

56
Q

what is anorectal genesis?

A

problems with blood supply to hindgut

57
Q

Which derivatives of the midgut and hindgut retain their mesenteries?

A 
o Jejunum
o Ileum
o Appendix
o Transverse colon
o Sigmoid colon
58
Q

Which derivatives of the midgut and hindgut become secondary retroperitoneal?

A

o Duodenum
o Ascending colon
o Descending colon
o Rectum (no peritoneal covering in distal 1/3)

Semester 3 - Gastrointestinal (17 decks)

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