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Anatomy II > GI system embryology > Flashcards

GI system embryology Flashcards

1
Q

Which arteries supply the different parts of the gut?

A

unpaired branches of abdominal aorta

  • truncus coeliacus → foregut
  • a. mesenterica sup. → midgut
  • a. mesenterica inf. → hindgut
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2
Q

What are the derivatives of the foregut?

A

pharynx → ampulla pancreatica

  • pharynx
  • lower resp. system
  • esophagus + stomach
  • duodenum proximal to opening of bile duct
  • liver + biliary apparatus + pancreas
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3
Q

How does the esophagus develop?

Where do its structures originate from?

A
  1. seperation from trachea by treacheoesophageal septum (cf. flashcards for resp. system)
  2. obliteration of lumen + recanalization

orgin:

  • endoderm → epithelium + glands
  • 4th + 6th pharyngeal arch → striated m.
  • splanchnic mesenchyme → smooth m.
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4
Q

How does the stomach develop?

A

slight dilation in caudal part of foregut in median plane

  1. dorsal border grows faster than ventral
    → curvatura gastrica major
  2. rotation 90° clockwise around longitudinal axis
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5
Q

Explain the innervation of the stomach w/r/t its rotation

A

since:

  • left side → ventral surface
    → ant. wall innervated by truncus vagalis sin.
  • right side → dorsal surface
    → post. wall → innervated by truncus vagalis dex.
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6
Q

How do you call the structure attaching to the stomach?

Where else does it attach?

What does it eventually form?

A

dorsal mesogastrium

  • attaches to: post. abdominal wall
  • contains: spleen, celiac artery
  • forms: omental bursa

ventral mesogastrium

  • attaches to: ant. abdominal wall
    • duodenum to liver
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7
Q

How is the omental bursa formed?

Which structures does it form?

A

clefts forming in dorsal mesogastrium coalesce and form foramen omentale, demarcates opening to omental bursa (sac formed during rotation of stomach)

forms:

  • superior recess persists dorsal to right lung
  • inferior recess → disappears as layers of omentum majus fuse
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8
Q

How does the duodenum develop?

A

section around junction btw foregut and midgut

  1. forms C-shaped loop (= ansa duodenalis)
  2. pushed into retroperitoneal position by developing stomach (not pars superior!) → ​sec. retroperitoneal
  3. lumen obliterates → recanalization
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9
Q

How do the liver and biliary apparatus develop?

A

outgrowth from distal part of foregut (= hepatic diverticulum) extends into septum transversum

  1. enlarges and divides into 2 parts btw ventral mesogastrium
    - cranial part: liver primordium
    * - caudal part:* gall bladder primordium
    - stalk of caudal part: ductus cysticus
    - stalk connecting both parts: common bile duct
  2. future common bile duct moves to dorsal aspect of duodenum as duodenum grows
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10
Q

How does the “interior” of the liver develop?

A

endodermal cells → cords of hepatocytes + endothelial lining of intrahepatic part of biliary apparatus

→ hepatic cords anastomose around hepatic sinusoids

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11
Q

When does hematopoiesis in the liver begin?

A

6th week → bright reddish color to the liver

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12
Q

When does bile formation begin?

How do you call the dark green intestinal contents?

A

12th week

meconium

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13
Q

The ventral mesentery gives rise to which structures?

A
  • omentum minus (= lig. hepatogastricum, lig. hepatoduodenale, lig. hepatoesophageale)
  • lig. falciforme
  • lig. coronarium
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14
Q

How does the pancreas develop?

A

endodermal cells from caudal end of foregut form pancreatic buds btw the layers of the mesentery

  • ventral pancreatic bud (near entry of bile duct)
  • dorsal pancreatic bud (larger + more cranially)
  1. duodenal rotation carries ventral pancreatic bud dorsally → posterior to dorsal pancreatic bud
  2. pancreatic buds fuse (ventral pancreatic bud → proc. uncinatus)
  3. pancreatic ducts fuse
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15
Q

Which pancreatic bud is responsible for which pancreatic duct?

A

ventral pancreatic bud:

  • ductus pancreaticus

dorsal pancreatic bud:

  • proximal part → ductus pancreaticus acc.
  • distal part → ductus pancreaticus
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16
Q

How does the “interior” of the pancreas develop?

A

endoderm of pancreatic buds forms network of tubules

  • cell clusters at end → pancreatic acini
  • groups of cells btw acini → islets of Langerhans
17
Q

What are the derivatives of the midgut?

A

ampulla pancreatica → 1st 2/3 of colon transversum

  • duodenum distal to opening of bile duct
  • small intestine
  • cecum + appendix
  • colon ascendens + 1st 2/3 of colon transversum
18
Q

How does the first part of the intestines develop?

A
  1. midgut enlarges
  2. physiological umbilical hernia
  3. rotation of midgut loop
  4. retraction of intestinal loops
  5. fixation of intestines

​meanwhile: cecum and appendix develop

19
Q

What is the umbilical hernia?

Why does it happen?

A

midgut loop (= ansa umbilicalis intestini) projects into umbilical vesicle through omphalomesenteric duct

due to:

  • rapidly growing midgut
  • relatively massive liver + kidneys
  • degenerating mesonephros
20
Q

What is the embryological origin of the Meckel’s diverticulum?

A

remnant of omphalomesenteric duct (= vitelline duct)

21
Q

Describe the rotation of the midgut loop.

A
  1. 90° counterclockwise rotation around axis of a. mesenterica sup.
    → cranial limb (small intestine) → to the left
    → caudal limb (large intestine) → to the right
  2. cranial limb forms intestinal loops
22
Q

Describe the retraction of the intestinal loops.

A
  1. enlargement of abdominal cavity → small intestine returns
  2. further 180° counterclockwise rotation
    → cecum + colon asc. → to the right

→ 270° in total

23
Q

Describe the fixation of intestines.

What are the final lines of attachment of omentum majus?

A

organs pushed into sec. retroperitoneal position
since their mesenteries fuse with post. abd. wall as they are pressed against it

  • rotation of intestine
    → duodenum (exc. pars superior)
    → head of pancreas
  • enlargement of intestine
    → colon asc.
    → colon desc.

⇒ final lines of attachment of omentum majus:
flexura duodenojejunalis → valva ileocecalis

24
Q

Explain how cecum and appendix develop.

A

cecal diverticulum appears on antimesenteric border of caudal midgut loop

  1. apex grows slower than rest → appendicular diverticulum
  2. appendix increases in length
  3. AFTER BIRTH: cecum grows unequally → appendix comes to lie on medial side
25
Q

What are the derivatives of the hindgut?

A
  • distal 1/3 of colon transversum
  • colon descendens, sigmoideum
  • rectum
  • sup. part of anal canal
  • epithelium of urinary bladder + most of urethra
26
Q

Which changes does the cloaca undergo?

A

dorsally/ventrally cloaca divided by urorectal septum

  1. septum grows towards cloacal membrane → seperation of
    - rectum + sup. part of anal canal
    - urogenital sinus
  2. lumen occluded + recanalization → anal pit

Anatomy II (13 decks)

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