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GI Midterm > GI Embryology > Flashcards

GI Embryology Flashcards

1
Q

Endoderm Contributions to GI Tract

A

Mucosal Epithelium and GI glands except for lower 1/3 anus

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2
Q

Mesoderm Contributions to GI Tract

A

Muscular Wall

Connective Tissue

Vasculature

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3
Q

Ectoderm Contributions to GI Tract

A

Enteric ganglia, nerves, glia (neural crest)

epithelium of lower 1/3 anus

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4
Q

Cranio-caudal folding of endoderm

  • when
  • what does it form
  • special components
A

4th week: trilaminar disc to cylinder

  • single tube of endoderm
  • forms foregut, midgut, hindgut
  • Vitelline Duct: narrowed opening to yolk sac
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5
Q

Foregut Derivative in GI

A

Esophagus to Upper Duodenum

- liver, pancreas, gallbladder

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6
Q

Midgut Derivative in GI

A

lower duodenum to splenic flexure

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7
Q

Hindgut Derivative in GI

A

splenic flexure to anal canal

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8
Q

Foregut arterial supply

A

celiac trunk

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9
Q

Midgut arterial supply

A

superior mesenteric artery

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10
Q

hindgut arterial supply

A

inferior mesenteric artery

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11
Q

Mesentery definition

A

double fold of peritoneum attaching intestines to abdominal wall
- prevent organs from floating around

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12
Q

Dorsal Mesentery

- which organs are derivatives

A
  • connects organs to dorsal body wall
  • greater omentum (gastrosplenic, gastrocolic, splenorenal ligaments)
  • small intestine mesentery
  • mesoappendix
  • transverse mesocolon
  • sigmoid mesocolon
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13
Q

Ventral Mesentery

- which organs are derivatives

A

-connects foregut to ventral wall from septum transversum to umblicial vein

  • lesser omentum (hepatoduodenal, hepatogastric ligament)
  • falciform , coronary, triangular ligament of liver
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14
Q

Intraperitoneal organs

A

suspended by mesentery

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15
Q

Retroperitoneal organs

A

excluded from peritoneal cavity

  • SAD PUCKER
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16
Q

Secondarily retroperitoneal

A

initially suspended within mesentery but later fused with body wall

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17
Q

Foregut development: organs (6)

A 
Esophagus
stomach
liver
gall bladder
pancreas
upper duodenum
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18
Q

Describe Rotation of Stomach

A

1) Dilated of foregut endoderm
2) Rotates 90 degrees
- left side moves ventrally
- right side moves dorsally
- vagus nerve follows rotation ( left vagus on ventral stomach, right vagus on right stomach)
3) lesser sac posterior to stomach
4) dorsal mesogastrium enlarges to form greater omentum

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19
Q

Hypertrophic Pyloric Stenosis

  • definition
  • causes
  • manifestation
A
  • narrowing of pyloric lumen-> obstruction of food passage

causes:

  • gradual hypertrophy of muscularis externa (thickened muscle)
  • inability of sphincter to relax bc of faulty NCC migration

Manifestation

  • mass at right costal margin
  • non- bilous vomiting with feeding
  • small stool
  • can’t gain weight

exposure to erythromycin is associated with it

20
Q

Liver Formation

  • when
  • germ layer
  • components
A

week 4

  • endoderm-> hepatocytes, bile duct, hepatic duct
  • splanchnic mesoderm-> stromal cells, kuppfer cells, stellate cell

hepatic diverticulum

  • endoderm
  • connection of diverticulum to foregut= common bile duct
  • hematopoietic organ
21
Q

Gallbladder formation

- two components

A

1) Cystic diverticulum
- second outpouching of common bile duct
- from hepatic diverticulum
- cystic duct
- direct lumen recanalization

2) bile formation
- week 12
- hepatocytes

22
Q

Biliary Atresia

  • symptoms
  • treatment
A

Obliteration of extrahepatic or intrahepatic ducts

  • inflammation replaces duct with fibrotic tissue

Symptoms:

  • progressive jaundice
  • white colored stool
  • dark urine

TX: liver transplant

23
Q

Pancreas formation

  • when
  • describe location
A

week 5: rotation of stomach and migration of liver

Two buds from foregut inferior to cystic diverticulum (endodermal)

  • have exocrine and endocrine parts
  • Ventral pancreatic bud-> ventral mesentery
  • Dorsal pancreatic bud-> dorsal mesentery

Ventral pancreatic duct, cystic duct, and common bile duct move posteriorly

Ventral duct fuse with dorsal duct

  • main pancreatic duct: connection to duodenum and ventral pancreatic duct
  • accessory pancreatic duct: remnants of dorsal duct to duodenum
24
Q

Ventral pancreas fate

A

uncinate process, part of pancreatic head

25
Q

Dorsal pancreas fate

A

pancreatic head, body, tail

26
Q

Pancreas Anomalies (3)

A

1) Accessory Pancreatic Duct
2) Pancreas Divisum
- ventral and dorsal parts fail to fuse by week 8
- asymptomatic, abdominal pain
3) Annular pancreas
- poor migration of pancrease-> pancreatic ring around 2nd part of duodenum
- duodenal obstruction/stenosis
- BILOUS vomiting
- low birth weight

27
Q

Spleen formation

  • when
  • derivative
A

Week 4: mesenchymal condensation in dorsal mesogastrium

Week 5: spleen form

** derived from mesoderm NOT endoderm

28
Q

What are the derivatives of the midgut?

A
  • lower duodenum (distal to bile duct)
  • jejunum
  • ileum
  • cecum
  • appendix
  • ascending colon
  • proximal 2/3 of transverse colon
29
Q

What is the timeline of development of the midgut including rotation?

A
  • midgut herniates out of umbilicus at week 6 (around day 50)
  • 90 degree counterclockwise (CCW) rotation
    • distal part develops cecum, proximal part becomes convoluted
  • body and abdominal cavity grows and midgut returns (day 70)
  • proximal returns first, passes under distal portion toward left (another 90 degree CCW)
  • distal portion returns (another 90 degree CCW)
30
Q

What is omphalocele?

A
  • fetal abdominal wall defect
  • 2.5/10,000 births
  • herniation through umbilicus with peritoneal covering
  • increased risk with trisomy 13 or 18
  • etiology:
    • herniated bowel does not fully retract
    • failure of lateral fold closure –> wall weakness –> bowel herniation
    • malformation of connective tissue of skin and hypaxial musculature of body wall –> wall weakness
31
Q

What is gastroschiscis?

A
  • herniation of abdominal contents through abdominal folds
  • 3-4/10,000 births
  • not covered by peritoneum
32
Q

What is the difference between omphalocele and gastroschiscis?

A

omphalocele: covered in peritoneum
gatrochiscis: not covered by peritoneum

33
Q

What is Meckel’s Diverticulum?

A
  • incomplete obliteration of vitelline (omphalomesenteric) duct
  • true diverticulum: all layers of bowel wall
  • most common congenital anomaly of GIT
  • rule of 2: 2x in males, 2 inches, 2 feet from ileocecal valve, 2% of population, 2 first years of life, 2 types gastric or pancreatic
  • usually clinically asymptomatic
  • abdominal swelling, obstruction, RLQ pain, GI bleed
34
Q

Yolk stalk connection pathologies

A
  • Meckel’s diverticulum
  • umbilical sinus
  • fibrous cord with immediate cyst
  • umbilicointestinal fistula
  • fibrous cord connecting SI to umbilicus
35
Q

What is malrotation/nonrotation of midgut loop?

A
  • completion of first 90 degree CCW rotation, but does not do remaining rotations
  • results in left sided colon and right sided intestines
  • 1/500 births
  • complications: formation of fibrous Ladd bands can lead to volvulus duodenal obstruction
36
Q

What is reverse gut rotation?

A
  • completion of 90 degree CCW rotation followed by 180 degree CW rotation
  • results in transverse colon posterior to duodenum
37
Q

What is volvulus?

  • complications
  • symptoms
  • when is there increased risk?
A
  • twisting of bowel around its mesentery
  • complications: obstruction and infarction
  • symptoms: acute abdominal pain, vomiting, GI bleeding
  • increased risk with gut rotation abnormalities
38
Q

Describe intestinal lumen formation

A
  • lumen temporarily obliterated due to endodermal proliferation
  • vacuoles form as endodermal cells regenerate –> recanalization of lumen
39
Q

What is duodenal stenosis?

A

partial occlusion of lumen due to incomplete recanalization

40
Q

What is duodenal atresia?

A

failure to recanalize –> complete occlusion of lumen

-associated with trisomy 21 (down syndrome)

41
Q

What is jejunal/ileal stenosis/atresia?

A
  • due to vascular insufficiency

- prominent abdominal distension with ileal atresia/stenosis

42
Q

What are the derivatives of the hindgut?

A
  • distal 1/3 transverse colon
  • descending colon
  • sigmoid colon
  • rectum
  • superior 2/3 anal canal (to pectinate line)
43
Q

Describe separation of cloaca

A
  • urorectal septum partitions cloaca into dorsal anorectal canal and ventral urogenital sinus
  • cloacal membrane ruptures –> opens urogenital sinus and anal canal to exterior
44
Q

Upper 2/3 of anal canal

  • germ layer
  • blood supply
  • innervation
A
  • endoderm
  • superior rectal A from IMA and superior rectal V to IMV –>portal V
  • lumbar and pelvic splanchnic nerves
45
Q

Lower 1/3 of anal canal

  • germ layer
  • blood supply
  • innervation
A
  • ectoderm
  • inferior rectal A from pudendal A and inferior rectal V to internal pudendal V–>internal iliac V–>IVC
  • pudendal N branches
46
Q

What is imperforate anus?

A
  • congenital defect
  • opening to anus is missing/blocked due to persistent anal membrane
  • 1/5000 births
  • low, intermediate, high distinction - relative to levator ani muscles and pelvic bony landmarks
47
Q

What is Hirschsprung’s disease?

A

AKA congeinital aganglionic megacolon

  • 1/500 live births
  • abscence of ganglionic plexus due to failure of NCC to migrate
  • presentation
    • intestinal wall hypertrophy proximal to aganglionic segment
    • lack of peristalsis (colon fails to relax)
    • abnormal colonic dilation/distension (megacolon)
  • treatment: surgical removal or constricted distal segment

GI Midterm (10 decks)

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