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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
Dorsal pancreas fate
pancreatic head, body, tail
26
Pancreas Anomalies (3)
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
Spleen formation - when - derivative
Week 4: mesenchymal condensation in dorsal mesogastrium Week 5: spleen form ** derived from mesoderm NOT endoderm
28
What are the derivatives of the midgut?
- lower duodenum (distal to bile duct) - jejunum - ileum - cecum - appendix - ascending colon - proximal 2/3 of transverse colon
29
What is the timeline of development of the midgut including rotation?
- 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
What is omphalocele?
- 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
What is gastroschiscis?
- herniation of abdominal contents through abdominal folds - 3-4/10,000 births - not covered by peritoneum
32
What is the difference between omphalocele and gastroschiscis?
omphalocele: covered in peritoneum gatrochiscis: not covered by peritoneum
33
What is Meckel's Diverticulum?
- 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
Yolk stalk connection pathologies
- Meckel's diverticulum - umbilical sinus - fibrous cord with immediate cyst - umbilicointestinal fistula - fibrous cord connecting SI to umbilicus
35
What is malrotation/nonrotation of midgut loop?
- 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
What is reverse gut rotation?
- completion of 90 degree CCW rotation followed by 180 degree CW rotation - results in transverse colon posterior to duodenum
37
What is volvulus? - complications - symptoms - when is there increased risk?
- twisting of bowel around its mesentery - complications: obstruction and infarction - symptoms: acute abdominal pain, vomiting, GI bleeding - increased risk with gut rotation abnormalities
38
Describe intestinal lumen formation
- lumen temporarily obliterated due to endodermal proliferation - vacuoles form as endodermal cells regenerate --> recanalization of lumen
39
What is duodenal stenosis?
partial occlusion of lumen due to incomplete recanalization
40
What is duodenal atresia?
failure to recanalize --> complete occlusion of lumen | -associated with trisomy 21 (down syndrome)
41
What is jejunal/ileal stenosis/atresia?
- due to vascular insufficiency | - prominent abdominal distension with ileal atresia/stenosis
42
What are the derivatives of the hindgut?
- distal 1/3 transverse colon - descending colon - sigmoid colon - rectum - superior 2/3 anal canal (to pectinate line)
43
Describe separation of cloaca
- urorectal septum partitions cloaca into dorsal anorectal canal and ventral urogenital sinus - cloacal membrane ruptures --> opens urogenital sinus and anal canal to exterior
44
Upper 2/3 of anal canal - germ layer - blood supply - innervation
- endoderm - superior rectal A from IMA and superior rectal V to IMV -->portal V - lumbar and pelvic splanchnic nerves
45
Lower 1/3 of anal canal - germ layer - blood supply - innervation
- ectoderm - inferior rectal A from pudendal A and inferior rectal V to internal pudendal V-->internal iliac V-->IVC - pudendal N branches
46
What is imperforate anus?
- 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
What is Hirschsprung's disease?
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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