EXAM #1: EMBRYOLOGY OF THE GI SYSTEM Flashcards Preview

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Flashcards in EXAM #1: EMBRYOLOGY OF THE GI SYSTEM Deck (54):
1

What germ layer do the stomodeum and protodeum develop from?

Ectoderm

2

What are the derivatives of the foregut?

Pharynx to duodenum distal to the bile duct, plus:
- Liver
- Biliary apparatus
- Pancreas
- Respiratory system

3

What artery supplies the foregut?

Celiac artery

4

What are the midgut derivatives?

Duodenum distal to the bile duct to the right half of the transverse colon

5

What artery supplies the midgut?

SMA

6

What are the derivatives of the Hindgut?

Distal half of the transverse colon to the superior part of anal canal, plus:
- Bladder epithelium
- Most of the urethra

7

What artery supplies the Hindgut?

IMA

8

What part of the primitive gut does the respiratory system develop from?

Foregut

9

Describe the normal development of the esophagus.

1) Single tube
2) Branching of a lung bud and foregut from common tuve
3) Trachea and respiratory passageway are separted by tracheoesophageal folds that form a septum
4) Esophagus elongates

****Note that growth of the epithelium in the lumen of the esophagus nearly obstructs the esophagus and then re-canalizes****

10

What is a Short Esophagus?

Failure of the esophagus to elongate pulls some of the stomach into the thoracic cavity that can lead to lung hypoplasia

11

What is esophageal atresia?

Failure of the esophagus to form

12

What is tracheoesophageal fistula?

- Proximal esophageal atresia
- Fistula forms between trachea and distal esophageal segment

13

What is esophageal stenosis?

Narrowing of the esophageal lumen

14

What are the three mechanisms that cause esophageal stenosis?

1) Sequestration of respiratory tissue elements
2) Myenteric plexus damage that causes hypertrophy (muscularis mucosa)
3) Mucosal diaphragm

15

What vascular anomaly can lead to esophageal stenosis?

4th branch on the LEFT side of the aortic arch; an anomalous right subclavian retroesophageal artery

16

What is the eponym for an anomalous right subclavian retroesophageal artery?

Lusorian artery

17

Describe the normal development of the stomach.

1) Expansion of primitive gut tube
2) More dorsal growth than ventral
3) 90 degree CLOCKWISE rotation
4) Slight pivot from growing esophagus

18

What part of the primitive stomach becomes the greater curvature?

Dorsal

19

What part of the primitive stomach becomes the lesser curvature?

Ventral

20

What is the LARP mnemonic?

Left= Anterior
Right= Posterior

21

What is Infantile Hypertrophic Pyloric Stenosis?

Hypertrophy of the pyloric sphincter in the neonate

22

What is the US characteristic that is pathognomonic for an Infantile Hypertrophic Pyloric Stenosis?

Sonolucent donut

23

What is the hallmark sign of Infantile Hypertrophic Pyloric Stenosis?

Non-bilious projectile vomiting

24

What causes duodenal stenosis?

Incomplete recanalization of the duodenum

25

What causes duodenal atresia?

Complete failure of recanalization

26

Mutations in what growth factor have been implicated in duodenal obstruction?

Sonic Hedge Hog

27

What x-ray findings is pathogmnemonic for duodenal atresia?

Double Bubble Sign

28

What is the most common cause of jejunal and ileal atresia?

Vascular accident, NOT failure of recanalization

29

What are the three stages of midgut rotation? What happens during these stages?

1) Herniation into the umbilical cord
2) Reduction back into the abdominal cavity
3) Fixation to posterior abdominal wall

30

What happens to the cranial and caudal limbs in midgut rotation? What is the axis of rotation?

Axis= SMA

Cranial= superior to SMA
- Undergoes rapid elongation
- Comes back in to left

Caudal= inferior to SMA
- Comes back in to right and inferior

31

What direction does the midgut rotate?

1) 90 degrees COUNTER-CLOCKWISE going OUT
2) 90 degrees counter clockwise
3) Additional 90 degrees COUNTER-CLOCKWISE

32

What is Omphalocele?

Failure of midgut reduction--results in external abdominal contents

33

What is a midgut nonrotation?

Midgut ROTATES, but only the first 90 degrees

34

What is the manifestation of midgut nonrotation?

Reversal of midgut contents--left sided-colon and right-sided small intestine

35

What is reversed rotation of the midgut?

270 degree rotation CLOCKWISE instead of counter- clockwise

36

What is the manifestation of reversed midgut rotation?

- Duodenum is anterior to the SMA
- Transverse colon is posterior to SMA

37

What is the mixed rotation of the midgut?

- Cranial limb rotates but caudal limb doesn't in first rotation
- 2nd rotation, only caudal limb rotates

38

What is the manifestation of mixed rotation of the midgut?

1) Cecum lies inferior to pylorus
2) Peritoneal bands form over duodenum
3) Duodenal obstruction
- Peritoneal bands
- Volvulus

39

How does a midgut volvulus appear on imaging?

1) "Corkscrew sign" on CT
2) Whirpool sign on US

40

What is a Meckel's Diverticulum?

Persistence of the vitelline duct that forms an outpocketing of the ileum--a TRUE diverticulum

41

What type of diverticulum is a Meckel's Diverticulum?

True--all walls involved

42

What causes ulceration of a Meckel's Diverticulum?

Heteroptoic parietal cells that screte HCl

43

How is the cloaca normally partitioned?

1) Urorectal septum divides the cloaca (terminal hindgut) into dorsal and ventral portions
- Ventral= urogenital sinus
- Dorsal= rectum
2) Urorectal septum contacts cloacal membrane forming:
- Anal membrane
- Urethral membrane
3) Anal membrane lies at bottom of proctodeum

44

What is the division of the dual derivation of the anal canal?

Pectinate line
- Proximal= hindgut
- Distal= ectoderm

45

What is the white line in the anal canal?

Division between internal and external sphincters

46

What arteries and veins supply the anal canal from the hindgut?

Superior rectal artery and veins

47

What lymph nodes supply the anal canal above the pectinate line?

IM

48

What arteries and veins supply the anal canal below the pectinate line?

Inferior rectal

49

What lymph nodes drain the anal canal distal to the pectinate line?

Superficial inguinal

50

Describe the innervation of the anal canal.

Superior to pectinate line= ANS

Inferior to pectinate line= Inferior rectal nerve

****No pain with issue superior to pectinate line*****

51

What is a Congenital Megacolon?

Absence of Myenteric Plexus in the colon that leads to contraction and dilation similar to achalasia

52

What is an annular pancreas?

Bilobed pancreas wraps around the duodenum

53

What can an annular pancreas cause?

Duodenal stenosis

54

What sign can be present with an annular pancreas on x-ray?

Double bubble