Embryology of the GI tract Flashcards Preview

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Flashcards in Embryology of the GI tract Deck (94):
1

When in gestation does the gut begin to develop?

4th week

2

What are the foregut derivatives?

Pharynx to duodenum distal to bile duct
Liver
Biliary apparatus
Pancreas
Respiratory system
Celiac artery

3

What are the midgut derivatives?

Duodenum to distal bile duct to right half or 2/3 of the TC SMA

4

What are the hindgut derivatives?

DIstal to transverse colon to the superior part of the anal canal
-Bladder epithelium
-Urethra
-IMS

5

Foregut, midgut, or hindgut: liver

Foregut

6

Foregut, midgut, or hindgut: IMA

Hindgut

7

Foregut, midgut, or hindgut: SMA

Midgut

8

Foregut, midgut, or hindgut: biliary appratsu

Foregut

9

Foregut, midgut, or hindgut: respiratory tract

Foregut

10

Foregut, midgut, or hindgut: Pancreas

Foregut

11

Foregut, midgut, or hindgut: celiac artery

Foregut

12

What is the division in the large intestines from the midgut and the hindgut?

Halfway through to 2/3 through is the midgut. Rest is hindgut

13

What is the stomodeum? What is it lined with?

Primitive mouth
Ectoderm

14

What is the gut tube lined with: endoderm, ectoderm, or mesoderm?

Endoderm

15

What is the end of the primitive gut tube called? What is this lined with?

Proctodeum--lined with ectoderm

16

What layer of the developing embryo gives rise to most of the musculature of the GI tube?

Mesoderm

17

What are the muscles that are associated with the mouth derived from?

pharyngeal arches

18

Foregut, midgut, or hindgut: larynx/trachea

Foregut

19

What are the folds that separate the trachea from the esophagus in the developing embryo?

tracheoesophageal folds

20

In the developing GI tube, what is the initial part of the tube that buds off to form the trachea and respiratory system called?

Lung bud

21

What is the septum that develops between the esophagu and the trachea?

Tracheo-esophageal septum

22

When in development does the trachea/esophagus form?

4th week

23

What happens if there is a short esophagus?

Pulls the stomach into the thoracic cavity

24

What happens to the esophagus lumen as growth continues?

First becomes obliterated by proliferating cells, then subsequently recanualizes

25

What is an esophageal atresia?

Failure of the esophagus to fully connect

26

What is most common form of esophageal/tracheal defect?

Atresia of the proximal esophagus, and fistula between the distal part and the trachea

27

Where do fistula between the trachea and the esophagus usually occur?

Mid to distal esophagus

28

What are the three mechanisms that bring about esophageal stenosis?

1. Stenotic region contains sequestered respiratory tissue elements
2. Fibromuscular hypertrophy d/t myenteric plexus damage
3. Mucosal diaphragm is present

29

What layer of the GI tract is the myenteric plexus in?

Between the two layers of the muscularis externa (inner circular layer, outer longitudinal layer)

30

What is the lusoria artery? What does this cause?

Failure of the Right brachiocephalic trunk to form, leaving the right common carotid branching directly off of the aorta, and an artery coming off of the left side of the trachea to form the right subclavian

May cause obstruction of the trachea

31

What part of the stomach grows faster:ventral or dorsal side?

Dorsal side

32

Which way does the GI tract rotate?

Clockwise

33

Which vagus nerve most anteriorly: the right or left?

Left

34

What is the acronym for remembering which vagal trunk is anterior and which is posterior??

LARP (left anterior, right posterior)

35

When does development of the stomach begin?

4th week of development

36

What is infantile pyloric stenosis?

Marked thickening of the pylorus in the muscularis externa

37

What is the US landmark that can be seen with infantile pyloric stenosis?

Sonolucent donut

38

What are the ssx of infantile hypertrophic pyloric stenosis?

Projectile vomiting (without bile)

39

What is the treatment for infantile pyloric stenosis?

Myotomy

40

When in development does the duodenum being to develop?

4th week

41

What is the arterial supply to the duodenum? Why?

Celiac and SMA since it's the junction between the foregut and the midgut

42

Which way does the duodenum rotate in development?

Clockwise (just like the stomach)

43

Junction of the caudal and cranial regions of the duodenum is just distal to what structure?

Common bile duct

44

What happens to the lumen of the duodenum in development? When does this occur?

Obliteration of the lumen, and subsequent recanalization

5th-8th week

45

What are the causes of duodenal obstruction? (5)

a. Incomplete recanalization (stenosis), usually
b. Annular pancreas (stenosis)
c. Recanalization does not occur – atresia
d. Mutations in sonic hedgehog signaling have been implicated
e. Obstruction of jejunum or ileum is due to a vascular accident

46

What is the common radiological sign of duodenal atresia?

Double bubble sign--dilation of areas immediately proximal and distal to the atresia

47

What is the most frequent cause of jejunal and ileal atresia and stenosis?

Vascular accident--NOT a failure to recanalize

48

What is the most frequent site of duodenal stenosis?

Ampulla of Vater

49

What are the three stages of midgut rotation?

-Herniation into umbilical cord
-Reduction from umbilical cord
-Fixation

50

When does development of the midgut start?

6th week

51

What is the reason for the umbilical herniation seen in the midgut development?

not enough room in the abdominal cavity for a rapidly growing midgut

52

Where is the yolk stalk attached to the midgut?

apex of the midgut loop

53

What separate the cranial and caudal limbs of the midgut during development? How do the two rotate about this?

SMA--rotate counterclockwise

54

Which part of the midgut GI tract herniates into the umbilical cord (cranial or caudal)? What happens to relieve this?

Cranial--elongation

55

How many degrees does the midgut rotate about the SMA?

270

56

The cranial limb of the midgut moves to the right or to the left? How about the caudal part?

Cranial = right
Caudal = left

57

When in development does the midgut return to the abdomen? Which part returns first: cranial or caudal portion

10th week--cranial returns first

58

What is it called when the intestines fails to reduce back into the abdominal cavity?

Omphalocele

59

What is an omphalocele? What is the cause?

When the intestines fails to reduce back into the abdominal cavity d/t incomplete closure of the abdominal wall

60

What happen in the nonrotation defect of the midgut? Symptoms of this?

first 90 degrees of rotation occurs, but not more, leading to a left sided colon

Usually asymptomatic

61

What is a reversed rotation? Symptoms? Why?

Midgut loop rotates 270 in a clockwise direction, leading to a duodenum that is anterior to the SMA, and a transverse colon that is posterior to the SMA

Stenosis d/t SMA

62

What is mixed rotation of the midgut? Symptoms?

mixed rotation (90 degrees for cranial, 180 for caudal) leading to cecum that lies inferior to the pylorus, and peritoneal bands descending over the duodenum

Peritoneal bands and volvulus usually cause duodenal obstruction

63

How are volvuli formed in mixed rotation?

90 degrees of rotation of the cranial limb, and 180 degrees of rotation for the caudal limb, leads to twisting about one another

64

What is Meckel's (ileal) diverticulum? What can cause ulceration of this?

Ileal diverticulum that represents the remnant of the proximal part of the yolk stalk

Parietal cells can form here, leading to acid production

65

When do the cecum and appendix appear in development?

6th week

66

What part of the intestines is not fused to the peritoneum?

Transverse colon

67

What is the cause of an umbilical hernia?

Intestine do return to the abdominal cavity but then herniate prenatally or postnatally

68

What is the goal of partitioning the cloaca?

Differentiating the urinary system and the GI tract

69

What are the two division of the cloaca?

Urogenital sinus

Rectum

70

What separates the cloaca?

Wedge of mesenchyme

71

When does the urorectal septum fuse with the cloacal membrane?

7th week

72

What is the line that separates the proximal and distal portions of the anal canal? What is the proximal part derived from? Distal?

Pectinate/dentate line
Proximal derived from hindgut
Distal derived from proctodeum

73

What is the lymph drainage from distal segment of the anal canal?

Inguinal lymph nodes

74

What is the lymph drainage of the proximal segment of the anal canal, above the pectinate line?

IM lymph nodes

75

What is the nerve supply above and below the pectinate line?

Above - ANS

Below = inferior rectal n

76

What is the arterial supply above and below the pectinate line?

Above = superior rectal a
Below = infection rectal a

77

What is Hirschsprung's disease?

Failure of the development of the Myenteric plexus in the intestines, leading to toxic megacolon

78

What is a persistent cloaca?

When the cloaca does not close, leading to one orifice for GI tract, urinary, and genital system

79

What is persistent anal membrane?

failure to open the anal canal, leading to atresia

80

What is an anal pit?

When the anal canal deviates anteriorly into the perineum

81

What is a rectovaginal fistula?

Anal canal/vaginal fistula

82

What is a rectourethral fistula?

Poopy urethra

83

How do the liver and biliary apparatus arise?

as a ventral outgrowth from the caudal part of the foregut

84

What are the 2 parts of the liver bud as it forms?

Cranial and caudal parts

85

What does the cranial part of the liver bud form?

Liver

86

What does the caudal portion of the liver bud form?

Gallbladder and cystic duct

87

What is Alagille syndrome?

Familial intrahepatic cholestasis caused by a decreased number of bile ducts in the portal spaces

88

Which bud of the pancreas is larger: the dorsal or ventral portion?

Dorsal

89

As the duodenum rotates (___), what happens to the pancreas?

Clockwise

ventral pancreatic bud mashes into the dorsal bud

90

Most of the pancreas is derived from which pancreatic bud?

Dorsal bud

91

The main pancreatic duct forms from what?

Duct of the ventral bud, and the distal part of the dorsal bud's duct

92

How does an annular pancreas arise? Problems?

Bifid ventral bud

May cause GI obstruction

93

What is pancreatic divisum?

Results when the ventral and dorsal pancreatic ducts do not fuse, forcing pancreatic secretions out of the tiny minor sphincter of the pancreas

94

What is the main issue with Pancreas divisum?

May predispose to chronic pancreatitis