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GI System > Development Of The Gut 3,4 > Flashcards

Development Of The Gut 3,4 Flashcards

1
Q

What are 4 things the Midgut gives rise to?

A
  • Small Intestine, including most of duodenum
  • Caecum and appendix
  • Ascending colon
  • Proximal 2/3 of Trasverse Colon
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2
Q

What is the Primary Intestinal Loop?

How is it connected to the Yolk Sac?

What are its 2 ends?

A
  • An enormous elongation of the midgut that has ran out of space, so makes a loop around the Superior Mesenteric Artery
  • By Vitelline Duct
  • Has a Cranial and Caudal limb
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3
Q

In week 6, what happens to the Primary Intestinal Loop?

What else happens?

A

Elongates very rapidly and herniates into Umbilical cord

Liver also grows rapidly (abdominal cavity too small for both so intestine herniates)

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4
Q

What happens to the Primary Intestinal Loop once it has formed?

A
  • Cranial end (Small Intestine) elongates
  • Loop undergoes 3 90 degree clockwise rotations
  • Small intestine finishes on the left and large intestine on the right
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5
Q

What happens to the Cecum between rotations 2 and 3?

A

Descends from its original position, where the liver would be

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6
Q

What should have happened to the intestinal loop by week 10?

A

Should have returned to abdominal cavity

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8
Q

Reversed rotation is a developmental problem associated with the Rotation of the Primary Intestinal Loop.

Describe it
What do we end up with?

A
  • Midgut loop makes 1 90 degree Anti-Clockwise rotation instead of 3 clockwise ones
  • Transverse colon ends up posterior to duodenum
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9
Q

What is an Omphalocoele?

A

This is when the rotated midgut loop fails to return to abdominal cavity by week 10 (Still remain in umbilical cord)

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10
Q

What are 2 Anterior Ab Wall defects of the Midgut

A
  • Omphalocoele

- Gastroschisis

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11
Q

Malrotation is a developmental problem associated with the Rotation of the Primary Intestinal Loop.

Describe it
What do we end up with

A
  • This is when only 1 (as opposed to 3) 90 degree rotation is made
  • Left sided colon
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12
Q

Describe Gastroschisis (sometimes confused with Omphalocoele)

A
  • Failure of the abdominal wall to close during lateral folding of the embryo
  • Leaves gut tube and derivatives outside body cavity
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13
Q

Compare the;

  • Mortality rate
  • Quality of gut development

in Omphalocoele and Gastroschisis

A

Omphalocoele:

  • Higher (More associated developmental abnormalities)
  • Semi normal (Not exposed to amniotic fluid)

Gastroschisis:

  • Lower
  • Negatively affected, as herniated contents not covered in peritoneum
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14
Q

The Vitelline Duct is the connection between midgut and yolk sac, and should regress by week 7.

What are 3 possible abnormalities when it remains?

A
  • Vitelline Cyst
  • Vitelline Fistula
  • Meckel’s Diverticulum
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15
Q

Describe a Vitelline Cyst

Describe a Vitelline Fistula

A

Cyst:
- Patent middle section of previous Vitelline Duct

Fistula:
- Vitelline Fistula remains completely intact, connecting midgut and umbilicus (Fetal matter can exit here)

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16
Q

Describe a Meckel’s Diverticulum (most common Vitelline duct abnormality)

A
  • Essentially another appendix, but off of the small intestine
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17
Q

With reference to Meckel’s Diverticulum, what is the Rule of 2s?

A
  • 2% of population
  • 2 feet proxima to ileo-caecal valve
  • Usually detected in under 2s
  • 2:1 ratio male: female (more common in males)
18
Q

In some gut structures, cell growth becomes so rapid that the lumen is partially/ completely closed off.

What process occurs to restore the lumen?
What can partial/ complete failure of the process lead to?

A
  • Recanalisation occurs
  • Partial failure-> Stenosis (Lumen narrowed, mostly in duodenum)
  • Complete failure-> Atresia (Lumen obliterated/ no lumen)
19
Q

Describe Pyloric Stenosis

Describe its incidence

What is it characterised by?

A
  • Hypertrophy of circular muscle in region of pyloric sphincter (NOT a recanalisation failure)
  • Common stomach abnormality in infants
  • Projectile vomiting, caused by narrowing of exit from stomach
20
Q

What are 5 things the Hindgut gives rise to?

A
  • Distal 1/3 of transverse Colon
  • Descending colon
  • rectum
  • superior part of anal canal
  • epithelium of urinary bladder
21
Q

Describe how the Cloca is separated into Urogenital and Ana structures in week 4-7

A

Urorectal Septum (wedge of mesoderm) descends, dividing Cloaca into an anterior Urogenital Sinus and posterior Anorectal canal

22
Q

In Week 7, what happens to the Cloacal membrane?

A

Ruptures, opening anorectal canal to amniotic fluid

23
Q

What is the Proctodeum

A

The ectoderm covering a depression where the anus is going to be

24
Q

Describe the development of the anal canal

A
  • When anal membrane rutures the cloacal membrane, some Proctodeum enters the anal canal
  • Hence the anal canal is split into Superior( Deeper) and Inferior parts
25
Q

What is the Pectinate/ dentate line?

A

An imaginary line between the histologically distinct Superior and Inferior parts of the anal canal

(These parts have a different arterial supply, innervation, venous and lymphatic drainage)

26
Q

Compare the parts of the anal canal Above and Below the Pectinate line in regards to Arterial supply

A

Above/ Superior part: Inferior Mesenteric Artery

Below/ Inferior part: Pudendal artery

27
Q

Compare the parts of the anal canal Above and Below the Pectinate line in regards to Innervation

A

Above:
- S2,3,4 Pelvic Parasympathetics

Below:
- S2,3,4 Pudendal nerves

28
Q

Compare the parts of the anal canal Above and Below the Pectinate line in regards to Lymphatic drainage

A

Above:
- Internal iliac nodes

Below:
- Superfical Inguinal nodes

29
Q

Compare the parts of the anal canal Above and Below the Pectinate line in regards to Epithelia type

A

Above:
- Columnar (Like in rest of gut)

Below:
- Stratified squamous

30
Q

Describe the possible sensations Above and Below the Pectinate line

A

Above:
- Only stretch (Chemical injury can lead to vague pain, however)

Below:
- Temperature, touch and pain sensitive

31
Q

3 Hindgut abnormalities are

  • Imperforate anus
  • Anal/ anorectal agenesis
  • Hindgut fistulae

State their causes

A

IA: (No anal sphincter)
- Failure of anal membrane to rupture

AA: (anus doesn’t form)
- Problems with blood supply

HF: (Between rectal and anal section, and either bladder or vagina)
- Abnormalities during development

32
Q

List 4 structures of midgut/ Hindgut with fused mesenteries

A
  • Ascending colon
  • Descending colon
  • Duodenum
  • Rectum (No peritoneal covering in distal 1/3)
33
Q

Why are Omphalocoeles not exposed to any amniotic fluid?

State and explain the reason omphalocoeles have a high mortality rate, despite semi-normal development of the gut

A
  • They have a covering of peritoneum

- Associated with other genetic developmental abnormalities

GI System (26 decks)

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