1 - Development of the Abdominal Viscera Flashcards

1
Q

Objectives: Explain embryonic origin of adult abdominal viscera

Ventral Mesentery Origin + Named Parts (Falciform, Lesser Omentum, Hepatogastric, Hepatoduodenal)

A
  • Ventral Mesentery: Origin
    • Growth of liver causes bulge into abdominal cavity; pulling Septum transversum
    • Double Layer of Peritoneum (Ventral Mesentery) suspends between foregun and anterior abdominal wall
    • = Derived from Inferior Region of Septum Transversum
  • Ventral Mesentery: Named Parts
    • Falciform Ligament
      • Connects liver to abdominal wall; free margin carriers umbilical vein
    • Lesser Omentum
      • Connects liver to foregut
    • Hepatogastric Ligament
      • Connects liver to stomach
    • Hepatoduodenal Ligament
      • Connects liver to duodenum
      • Carries portal triad: Hepatic A., Portal V., Bile Duct
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2
Q

Objectives: Explain developmengal basis of peritoneal-organ relationships

A
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3
Q

Objectives: Explain developmental basis of congenital malformations

A
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4
Q

Objectives: Explain the clinical significance of dual innervation and blood supply to the anal canal

A
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5
Q

Explain the development of the esophagus?

Region of gut?

A
  • Esophagus:
    • Region: Foregut
    • Formed by tracheoesophageal septum in foregut tube
    • Separated from trachea by esophagotracheal ridge
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6
Q

Explain the development of the stomach

Region of gut?

Impact on Vagus N.?

A
  • Stomach
    • Region: Foregut
    • Starts as dilation in tube
    • Dorsal Surface grows faster (becomes greater curvature)
    • Rotates 90 degrees and slightly clockwise
    • Rotation results in formation of Lesser Sac
  • Impact of Vagus: Rotation of Stomach spins them
    • Anterior = Left
    • Posterior = Right
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7
Q

Explain the development of the liver?

Region of gut?

A
  • Liver:
    • Region: Foregut
    • Develops as bud - Hepatic Diverticulum off of foregut
    • Grows ventral, pushing into inferior septum transversum
      • ​Growth pulls Septum Transversum along; liver becomes suspended by Ventral Mesentery
    • Septum transversum becomes Central Tendon of Diaphragm; not covered by visceral peritoneum (bare area)
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8
Q

Explain the development of the Gall Bladder and Pancreas

What becomes the bile duct?

What causes migration of ventral pancreas and bile duct?

What occurs as pancreatic buds fuse; and what is the fate of the ventral and dorsal ducts?

What is unique about the ventral duct?

A
  • Arise from Hepatic Diverticulum
  • Dorsal Pancreas develops as bud off dorsal developing duodenum
  • The Common Stalk of the Liver and Gall Bladder becomes the bile duct
  • Rotation of duodenum causes ventral pancreas and bile duct to migrate dorsally
  • As pancrease fuses, ducts anastomose
    • Ventral Duct = Main pancreatic duct; opens with common bile duct on 2nd part of duodenum
      • Smaller duct, initial development with bile duct drives persistence as main duct
    • Dorsal Duct = May persist as accessory pancreatic duct
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9
Q

Clinical: Annular Pancreas

A
  • Rare congenital abnormality
  • Ring of pancreatic tissue encircles descending portion of duodenum
  • Cause: Incomplete rotation of the pancreatic ventral bud
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10
Q

Explain the development of the spleen?

How is it unique?

A
  • Not an outgrowth of the gut
  • Forms as independent condensation of mesoderm
  • Part os mesentry fuses with posterior abdominal wall
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11
Q

Explain midgut development

What is Physiological Umbilical Herniation?

Gastroschisis

Omphalocele

A
  • Liver and midgut grow fast; as midgut elongates, intestinal loops project into the umbilical cord (Physiological Umbilical Herniation); normal!
  • Gastroschisis: Ventral body wall defect that results in herniation of intestinal loops into the amniotic cavity; caused by failure of body wall to close
  • Omphalocele: Ventral body wall defect that results when parts of the gut tube that normally herniate into the umbilical cord to fail to return to abdominal cavity
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12
Q

Explain the concept of midgut rotation

How many times does it rotate?

What is Meckle’s Diverticulum?

A
  • When intestines project into umbilical cord, midgut loop rotates 90 degress CCW along axis of Superior Mesenteric Artery and Vitelline Duct
  • Cecum forms as a swelling on the distal (caudal) loop
  • As intestines return to abdomen, they rotate another 180 degrees CCW (270 deg total)
  • Meckle’s Diverticulum: Persistence of Vitelline Duct
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13
Q

Explain hindgut development

Cloaca?

Proctoderm?

What is the fully formed anal canal derived from? What is the separation of these sources?

A
  • Cloaca: Part of hindgut proximal to the cloacal membrane
    • Urogenital Septum divides into:
      • Urogenital Sinus (Anterior)
      • Anorectal Canal (Posterior)
  • Proctoderm: Indentation of body wall that pushes inward toward anorectal canal to form distal opening of tube
  • The fully formed anal canal is derived from both cloaca (hindgut) and proctodeum (body wall); their separation is the Pectinate Line
    • ​Above Line - Inferior Mesenteric / Autonomic
    • Below Line - Internal Iliac / Spinal Nerves
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