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GI > Development Of Midgut And Hindgut > Flashcards

Development Of Midgut And Hindgut Flashcards

0
Q

How does the midgut start to develop?

A

Begins as a short tube, elongates enormously until it has run out of space
It then forms a primary intestinal loop

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1
Q

What structures does the midgut give rise to?

A 
Small intestine
Caecum
Appendix
Ascending colon
Prox two thirds of transverse colon
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2
Q

PICTURESGive features of the primary intestinal loop

A

The superior mesentric artery is its axis
It is connected to the yolk sac by the vitelline duct
Has cranial and caudal limbs

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3
Q

Why does physiological herniation occur?

A

Primary intestinal loop grows so rapidly at he same time as the liver. The abdominal cavity is too small to accommodate them so intestines herniate into umbilical cord

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4
Q

In which week does the physiological herniation occur?

A

6

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5
Q

PICTURE What happens in the first 90* turn?

A

The distal part of the gut tube is left and the proximal part is right

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6
Q

PICTURE What happens after the first 90* turn?

A

The distal part develops a bulge which will become the caecum/caecum bud
The proximal part becomes convoluted

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7
Q

PICTURE How does the midgut return to the abdominal cavity?

A

Proximal part returns first, passing under the distal part, making the second rotation
The distal limb then returns, making another rotation

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8
Q

What happens in the descent of the cecal bud?

A

Temporarily lies in the upper right quadrant, just beneath the liver
Descends down the right hand side of the abdominal cavity into the right iliac fossa
It develops a narrow diverticulum - the appendix

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9
Q

Derivatives of the proximal limb of the midgut?

A

Distal duodenum, jejunum, proximal ileum

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10
Q

Derivatives of the caudal/distal limb of the midgut?

A

Distal ileum, cecum, appendix, ascending colon, proximal two thirds of the transverse colon

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11
Q

What happens if there is incomplete rotation of the midgut?

A

When the midgut makes only one 90* rotation, colon and cecum are the first to return causing a left sided colon

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12
Q

What happens if there is reverse rotation?

A

Midgut makes a rotation clockwise

Transverse colon passes posterior to the duodenum

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13
Q

What is a vitelline cyst?

A

Caused by persistence of the vitelline duct in the middle but both ends form fibrous strands
A cyst forms in the middle portion

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14
Q

What is a vitelline fistula?

A

When the whole vitelline duct remains patent over the entire length, forming a direct communication between the umbilicus and intestinal tract.

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15
Q

What is a Meckel’s diverticulum?

A

When a small portion of the vitelline duct persists, forming an outpocketing of the ileum

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16
Q

When can problems arise in a Meckel’s diverticulum?

A

If it contains heterotopic pancreatic tissue or gastric mucosa
Can cause ulceration, bleeding, perforation

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17
Q

Give the rule of twos about the Meckel’s diverticulum

A 
2% of population
2ft from ileocoecal valve
2 inches long
Detected in under 2s
2:1 male:female
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18
Q

When a Meckel’s diverticulum becomes inflamed, what is the main differential diagnosis?

A

Appendicitis

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19
Q

What incomplete recanalisation lead to?

A

Atresia of the tube affected - lumen is obliterated

Stenosis of the tube - lumen is narrowed

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20
Q

What can contribute to the incomplete recanalisation?

A

‘Vascular accident’

Impairment of blood supply to that part of the tube

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21
Q

Where can incomplete recanalisation occur?

A

Oesophagus
Bile duct
Small intestine
Duodenum (most common)

22
Q

What is pyloric stenosis?

A

Hypertrophy of the circular muscle in the region of the pyloric sphincter NOT A RECANALISATION FAILURE

23
Q

Clinical presentation of pyloric stenosis?

A

Projectile vomiting in infants

24
Q

What can ‘vascular accidents’ be caused by?

A

Malrotation
Volvulus
Body wall defect

25
Q

Clinical presentation of gastroschisis?

A

Protrusion of abdominal contenders through the body wall directly into the amniotic cavity.
Occurs lateral to umbilicus
Viscera are not covered by peritoneum or amnion

26
Q

Clinical presentation of an omphalocoele/examphalos?

A

Persistence of physiological herniation

Covering of amnion

27
Q

What has the worst survival rate? Omphalocoele or gastroschisis?

A

Omphalocoele

28
Q

Why is omphalocoele different to an umbilical hernia?

A

In an omphalocoele, there is no covering of skin or subcutaneous tissue, just a covering of amnion

29
Q

What does the hind gut give rise to?

A 
Distal third of the transverse colon
Descending colon
Rectum
Superior part of anal canal
Epithelium of urinary bladder
30
Q

What divides the anal canal and what does this indicate?

A

The pectinate line
Histologically distinct inferior and superior parts
Differences in arterial and venous supply, lymphatic drainage and innervation

31
Q

What is the cloaca and what is it covered by?

A

The part where the hindgut ends

Covered by the cloacal membrane

32
Q

What divides the cloaca and into what?

A

A wedge of mesoderm called the urorectal septum

Divided into the urogenital sinus anteriorly and anorectal canal posteriorly

33
Q

What is the blood supply above and below the pectinate line?

A

Above - inferior mesentric artery

Below - pudendal artery

34
Q

What is the epithelium above and below the pectinate line?

A

Above - simple columnar

Below - stratified squamous

35
Q

Lymph drainage above and below the pectinate line?

A

Above - internal iliac nodes

Below - superficial inguinal nodes

36
Q

Innervation above and below the pectinate line?

A

Above - S2, 3, 4 pelvic parasympathetic nerves

Below - S2, 3, 4 pudendal nerve

37
Q

What sensation can be felt above and below the pectinate line?

A

Above - stretch only

Below - temperature, touch, pain

38
Q

Is visceral pain well or poorly localised?

A

Poorly

39
Q

What is imperforate anus?

A

Failure of the anal membrane to rupture

40
Q

What other hindgut defects see there?

A 
Anal canal or anorectal agenesis
Hindgut fistulae (between anal canal and bladder)
41
Q

Which ligament connects the spleen and the stomach?

A

Gastrolienal ligament

42
Q

What structures does the dorsal mesentery become?

A

Greater omentum
Gastrolienal ligament
Mesocolon
Mesentery proper of the ileum and jejunum

43
Q

Which structures does the ventral mesentery become?

A

Lesser omentum from foregut to liver

Falciform ligament from liver to ventral body wall

44
Q

Blood supply of the midgut?

A

Superior mesentric artery and vein

45
Q

Innervation of the midgut?

A

Parasympathetic - vagus nerve

Sympathetic - superior mesenteric ganglion and plexus

46
Q

Blood supply of the hind gut?

A

Inferior mesenteric artery and vein

47
Q

Innervation of the hindgut?

A

Parasympathetic - pelvic - S2, 3, 4

Sympathetic - inferior mesenteric ganglion and plexus

48
Q

Give a timeline in weeks of gut development

A
  1. Tubular gut begins to form
  2. Primordium of liver, pancreas, and trachea. Buccopharyngeal membrane ruptures
  3. Expansion and early rotation of the stomach. Primary intestinal loop appears. Caecum and bile duct
  4. Liver growth. Herniation of intestinal loop. Appendix. Urorectal septum appears
  5. Pancreatic buds fuse. Cloacal partitioning complete. Rupture o cloacal membrane
  6. Anti-clockwise rotation of intestinal loop. Recanalisation
  7. Return of herniated loop
49
Q

What does the endoderm of the gut tube give rise to? (Below are just a few structures)

A

Liver
Pancreas
Lung

50
Q

What do you get if there is failure of the ceacal bud to descend?

A

Sub hepatic caecum

51
Q

What is the allantois?

A

Structure that serves as a respiratory and waste storage organ for embryos.
Extends from ventral region of urogenital sinus to umbilicus.

52
Q

What does a remnant of the allantois become in adult life?

A

A distal portion of the allantois called the urachus becomes a fibrous cord and forms the median umbilical ligament.

53
Q

What happens if the urachus remains patent?

A

Urachal fistula or cyst in this region

GI (21 decks)

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