Embryology of GI Flashcards

1
Q

Define Gastrulation

A

Occurs when a blastula (single layer) folds and enlarges to create a gastrula (three layers)

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2
Q

What are the three germ layers of a gastrula

A

ectoderm, mesoderm, endoderm

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3
Q

When does the primordial gut form

A

4th week

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4
Q

What is the cranial end closed by

A

oropharyngeal membrane

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5
Q

What is the caudal end closed by

A

cloacal membrane

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6
Q

What thee parts does the primordial gut tube divide into

A

foregut, midgut, hindgut

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7
Q

Endoderm of the primordial gut forms

A

most of gut, epithelium and glands

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8
Q

Epithelium from cranial and caudal end are derived from

A

ectoderm (stomodeum) and anal pit (proctodeum)

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9
Q

In 4th week the intra-embryonic coelom becomes

A

embryonic body cavity

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10
Q

Embryonic body cavity divides into

A

Pleural, Pericardial and Peritoneal cavities

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11
Q

Primordial pharynx derived from

A

foregut

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12
Q

Lower respiratory tract derived from

A

foregut

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13
Q

Oesophagus derived from

A

foregut

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14
Q

Stomach derived from

A

foregut

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15
Q

Duodenum (part above opening of bile and pancreatic duct) derived from

A

foregut

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16
Q

Liver derived from

A

foregut

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17
Q

Biliary apparatus derived from

A

foregut

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18
Q

Pancreas derived from

A

foregut

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19
Q

Oesophageal Atresia

A

congenital condition causing oesophagus to end in a blind end pouch. Caused by failure of recanalization

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20
Q

Tracheoesophageal fistula

A

abnormal connection in one or more places between the oesophagus and the trachea. Caused by abnormal deviation of trachea-oesophageal septum

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21
Q

What is a coelom

A

a cavity lined by an epithelium derived from mesoderm (organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks)

22
Q

Three main developments of the stomach

A
  1. Rotation of stomach – Rotates
    90 degree clock wise
  2. Mesenteries of stomach
  3. Formation of omental bursa (lesser sac)
23
Q

What is hypertrophic pyloric stenosis

A

blockage of the passage out of the stomach due to thickening (hypertrophy) of the muscle at the junction between the stomach and the intestines - treatment is surgical

24
Q

Development of liver

A

hepatic diverticular (liver bud) is a cellular extension of foregut endoderm that gives rise to the parenchyma of the liver

25
Q

Liver (duct) anomaly

A

accessory hepatic ducts (5%)

26
Q

Extrahepatic biliary atresia

A

one or more bile ducts are abnormally narrow, blocked, or absent

27
Q

Development of pancreas

A

formation of a ventral and a dorsal pancreatic bud

  • dorsal pancreatic bud forms the head, neck, body, and tail
  • ventral pancreatic bud forms the uncinate process
28
Q

Annular pancreas

A

ventral bud fails to migrate around the duodenum correctly

29
Q

What can an annular pancreas cause

A

duodenal stenosis

30
Q

Development of spleen

A

during the 5th week mesenchyme differentiates to form the spleen - spleen is a MESODERMAL derivative and not an endodermal derivative of the gut tube

31
Q

Distal part of duodenum derived from

A

midgut

32
Q

Jejunum derived from

A

midgut

33
Q

ileum derived from

A

midgut

34
Q

caecum derived from

A

midgut

35
Q

appendix derived from

A

midgut

36
Q

ascending colon derived from

A

midgut

37
Q

promixal 2/3rds of transverse colon derived from

A

midgut

38
Q

Midgut loop (main events)

A

Herniation – Physiological umbilical herniation

Rotation of midgut loop – 90 degrees counterclockwise in the umbilical cord

Retraction of intestinal loops – 180 degrees more counterclockwise rotation

Fixation of intestines

39
Q

remnants of the vitalline duct can cause

A

meckel diverticulum - slight bulge in the small intestine present at birth.
May form a vitalline cyst, fistula or ligament

40
Q

What is an omphalocele

A

herniation of abdominal viscera through an enlarged umbilical ring - may include liver, stomach, intestinal loops.
Viscera covered by a layer of amnion

41
Q

What is gastroschisis

A

Herniation of abdominal contents directly through the body wall into the amniotic cavity - not covered by peritoneum or amnion

42
Q

Distal 1/3rd of transverse colon derived from

A

hindgut

43
Q

descending colon derived from

A

hindgut

44
Q

sigmoid colon derived from

A

hindgut

45
Q

rectum derived from

A

hindgut

46
Q

upper part of anal canal derived from

A

hindgut

47
Q

lining of bladder and urethra formed from

A

endoderm of hindgut

48
Q

What is the cloaca

A

expanded terminal part of the hindgut and endoderm lined chamber

49
Q

Urorectal fistula

A

congenital defect in the urorectal septum resulting in passage of urine through the rectum

50
Q

Rectovaginal fistula

A

abnormal connection between the rectum and the vagina

51
Q

Rectoanal atresia

A

rare anorectal malformation associating a normal anal canal with a stricture or a complete rectal atresia

52
Q

Imperforate anus

A

failure of anal membrane to break down