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Embryology Flashcards

1
Q

Where does body cavity form from?

A

lateral plate mesoderm - divides into parietal (somatic) and visceral (splanchnic) mesoderm

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2
Q

parietal mesoderm

A

forms parietal serous membranes

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3
Q

visceral mesoderm forms?

A

visceral serous membranes and muscles/CT of guts

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4
Q

body wall defects due to failure of ventral body wall fusion

A

viscera herniates through defect:

  • ectopic cordis
  • gastroschisis
  • bladder/cloacal exstrophy
  • Cantrell’s pentology
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5
Q

dorsal mesentery

A
  • suspends gut tube to posterior body wall
  • extends from caudal foregut to hingut
  • mesoesophagus, greater omentum, splenorenal lig, phrenicocolic/splenic lig, mesentery proper, mesoappendix, transverse mesocolon, sigmoid mesocolon
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6
Q

ventral mesentery?

A

suspeds gut tube to anterior body wall - extends from foregut to proximal duodenum
- derivatives: lesser omentum (hepatogastric, hepatoduodenal ligmanets), falciform ligament, coronary and triangular ligament.

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7
Q

primary retroperitoneal

A

kidneys, ureters, bladder

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8
Q

secondary retroperitoneal

A
  • initially entire gut tube has dorsal mesentary, but fusion occurs: duodenum, ascending/descending colon; pancreas
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9
Q

peritonealized

A

stomach, spleen, Parts 1/4 of duodenum, jejunum, ileum, transverse and sigmoid colon

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10
Q

septum transversum forms…

A

plate of mesoderm which separates thoracic and peritoneal cavity.

  • forms bulk of diaphragm; muscle and central tendon of diaphragm
  • does not completely separate thoracic and abdominal cavities; leaves openings on either side of foregut called “pericardioperitoneal canals”
  • mesoderm forms in neck from cervical somites C3,4,5 = phrenic n.
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11
Q

pleuropericardial/peritoneal membranes

A
  • pleuripericardial separate pleural and pericardial cavities
  • pleuroperitoneal: separate pleural and peritoneal cavities
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12
Q

what four sources contribute to formation of diaphragm?

A

septum transversum: central tendon and muscle

- pleuroperitoneal membranes: central tendon

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13
Q

how does diaphragm position change?

A

mesoderm forms from cervical somites 3-5
will descend into thorax by week 8
innervation: motor: phrenic, sensory: phrenic to central tendon; intercostal nn. to muscle

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14
Q

Posterolateral defect

A

type of congenital diaph, hernia
cause: Failure of pleuroperitoneal membranes to form.

  • lungs and heart are compressed; common cuase of pulmonary hypoplasia
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15
Q

parasternal hernia

A

more common

cause: Small gap between sternal and costal portion of diaphragm.
- can cause strangulation of herniated gut

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16
Q

eventration of diaphragm

A

cause: Lack of muscle differentiation within diaphragm - failure of myotome migration
- results in abdomina viscera balooning, compression of lungs, and hypoplasia.

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17
Q

3 germ layers contribution to gut tube:

A
  1. endoderm: epithelium and glands (inner lining)
  2. mesoderm: connective tissue and smooth muscle
  3. ectoderm: epithelium at ends of tube
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18
Q

foregut

A

esophagus, stomach, parts 1/2 of duodenum; liver, gallbladder, pancreas, spleen.

  • celiac artery
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19
Q

midgut

A

3/4 of duodenum, small intestine, cecum, appendix, ascending colon, proximal 2/3 or transverse colon

  • SMA
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20
Q

hindgut

A

distal 1/3 of transverse colon, anal canal

IMA

21
Q

esophageal atresias/stenoses

A

Failure of gut to recanalize (can affect entire gut; most common in duodenum).

  • endoderm proliferates and forms a plug, recanalizations normally occurs and the plug is reopened.
  • can also be caused by malformation of tracheoesophageal septum
  • stenosis: incomplete recanalizations
  • atresia: no recanalization
22
Q

congenital hiatal hernia

A

Cause: Failure of esophagus to fully elongate.

- pulls stomach through diaphragm

23
Q

tracheoesophageal fistula

A

Cause: Deviation of tracheoesophageal septum

  • results in blind ending esophagus
24
Q

rotation of stomach

A
  • stomach rotates 90 clockwise around longitudinal axis: dorsal part (greater curvature)is on left, ventral part (lesser curvature) on right
  • stomach also rotates around anterioposterior axis: pyloric part moves upward and to right; cardiac portion moves down and to left
25
Q

omental bursa

A
  • when stomach rotates it stretches dorsal mesentery. the Omental bursa comes to lie inferior and posterior to stomach
  • during later development, the layers of the greater omentum fuse
  • results in formation of greater omentum
26
Q

pyloric stenosis

A

Cause: Pathological hypertrophy of pyloric sphincter.

  • results in occulsion of pyloric region; vomitting and no weight gain
27
Q

what does spleen form from?

A
  • forms from mesenchymal cells within the two layers of dorsal mesogastrium
  • rotation of gut results in spleen being on left side of ab. cavity
28
Q

liver and gallbladder formation?

A
  • hetpatic diverticulum: outgrowth from second portion of duodenum
29
Q

liver formation

A

endoderm gives rise to parenchyma; mesoderm gives rise to stroma
functions as a hematopoietic organ during 2nd month
bile formation begins week 12

30
Q

gallbladder and cystic duct formation

A
  • forms from an evagination of bile duct.

- because of rotation of foregut, bile duct passes posterior to duodenum

31
Q

extrahepatic biliary atresia

A
  • blockage of biliary duct due to lack of recanalization

- results in an underdeveloped liver

32
Q

formation of pancreas?

A

arises from endodermal outgrowths of duodenum (dorsal and ventral buds). rotation of duodenum causes fusion of buds. most of pancreas is derived from dorsal bud - ventral bud forms the head and uncinate process

  • main pancreatic duct derived from ventral pancreatic duct and distal dorsal pancreatic duct
  • accessory pancreatic duct derived from proximal part of dorsal pancreatic duct
33
Q

aberrant pancreatic tissue

A

Cause: Abnormal migration of pancreatic tissue.

can degrade surrounding tissue

34
Q

Annular Pancreas

A
  • atresia of pancreas b/c of bifid ventral pancreatic bud; during rotation the bifid bud encircles the duodenum.
  • after fusion of the pancreas, the annular tissue can constrict the duodenum
35
Q

duodenal atresia/stenosis

A

Cause : Failure of gut to recanalize (can affect entire gut; most common in duodenum).

  • often affecting 3///4th portions
  • digested food and bile are forcible vomited = green colord
  • distended epigastrium b/c overfilled stomach
  • baby not swallowing amnionic fluid - thus mother often has polydramnios
36
Q

Duodenum development

A

foregut: parts 1/2. midgut parts 2/3.

- as stomach rotates, pulls duodenum superirorly and to right, resulting in a C-shaped duodenum

37
Q

white vs. green vomit?

A

white vomit: proximal to 2nd part of duodenum

green: distal to 2nd part of duodenum

38
Q

midgut development

A

physiological herniation week 6
midgut rotates 270 counterclockwise
midgut retracts weeks 10-12 (jejunum enters first to lie on left side, cecum returns last to lie in RLQ)

39
Q

omphalocele

A

Cause : Midgut loop fails to retract into abdomen.

  • tissue protrudes through umbilicus and is covered by amniotic membrane
  • often part of more severe syndromes
40
Q

gastroschisis

A

Cause: Ventral body wall defect; gut herniates through weakness in abdominal wall.

  • typically lateral to umbilicus on right.
  • usually results from incomplete fusion of ventral body wall during folding
  • herniated bowe is NOT covered by amniotic membrane; bathed in amniotic fluid
41
Q

umbilical hernia

A

Cause: Weakness in skin of umbilicus

  • results when gut herniates into umbilical cord after returning to abdominal cavity
  • loops of bowel herniate through an impercetl closed umbilicus along midline
  • herniated tissue is covered by skin, subcutaneous tisue
42
Q

Ileal diverticulum

A

Cause: vitelline duct fails to regress
2% of pop, 2x more likely in males, 2 feet distal of ileum, 2 inches long, 2% become symptomatic
- presents similar to appendicitis, but appendicitis is rare in toddlers

43
Q

Malrotation of gut

A

may result in volvulus and potential loss of blood sypply

44
Q

atresias/stenoses of midgut

A

cause: recanalization defect or ischemia

45
Q

retrocolic hernia

A

entrapment of small intestine behind colon
- can be due to failure of ascending colon to become retroperitoneal, resulting in a long mesocolon which may allow abnormal movements and potentially volvulus of the colon

46
Q

hindgut development

A
  • cloaca: distal most portion of gut tube; endoderm lined cavity which will contribute to formation of hindgut and urogenital system
  • urorectal septum divides cloaca into urogenital sinus and anorectal canal
  • Cloacal membrane ruptures during week 7
  • pectinate line; marks division between ectoderm/endoderm
47
Q

hirschprung’s disease (congenital megacolon)

A

Cause: failure of neural crest to migrate into gut (usually hindgut)

  • results in absence of parasympathetic ganglia, thus a portion of gut is paralyzed, and tremendous distension of colon occurs
  • fecal matter is blocked in the paralyzed portion
48
Q

fistulas and atresias of hindgut

A

Cause: malformation of urorectal septum

  • rectourethral and rectovaginal fistulas result from an anterior displacement of the hindgut.
  • rectoanal atresias result from loss of vascular suppply or failure of recanalizations
49
Q

imperforate anus

A

cause: failure of cloacal membrane to rupture

- blocked anus

GI (12 decks)

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