Embryology of the GI tract Flashcards
1
Q
When in gestation does the gut begin to develop?
A
4th week
2
Q
What are the foregut derivatives?
A
Pharynx to duodenum distal to bile duct Liver Biliary apparatus Pancreas Respiratory system Celiac artery
3
Q
What are the midgut derivatives?
A
Duodenum to distal bile duct to right half or 2/3 of the TC SMA
4
Q
What are the hindgut derivatives?
A
DIstal to transverse colon to the superior part of the anal canal
- Bladder epithelium
- Urethra
- IMS
5
Q
Foregut, midgut, or hindgut: liver
A
Foregut
6
Q
Foregut, midgut, or hindgut: IMA
A
Hindgut
7
Q
Foregut, midgut, or hindgut: SMA
A
Midgut
8
Q
Foregut, midgut, or hindgut: biliary appratsu
A
Foregut
9
Q
Foregut, midgut, or hindgut: respiratory tract
A
Foregut
10
Q
Foregut, midgut, or hindgut: Pancreas
A
Foregut
11
Q
Foregut, midgut, or hindgut: celiac artery
A
Foregut
12
Q
What is the division in the large intestines from the midgut and the hindgut?
A
Halfway through to 2/3 through is the midgut. Rest is hindgut
13
Q
What is the stomodeum? What is it lined with?
A
Primitive mouth
Ectoderm
14
Q
What is the gut tube lined with: endoderm, ectoderm, or mesoderm?
A
Endoderm
15
Q
What is the end of the primitive gut tube called? What is this lined with?
A
Proctodeum–lined with ectoderm
16
Q
What layer of the developing embryo gives rise to most of the musculature of the GI tube?
A
Mesoderm
17
Q
What are the muscles that are associated with the mouth derived from?
A
pharyngeal arches
18
Q
Foregut, midgut, or hindgut: larynx/trachea
A
Foregut
19
Q
What are the folds that separate the trachea from the esophagus in the developing embryo?
A
tracheoesophageal folds
20
Q
In the developing GI tube, what is the initial part of the tube that buds off to form the trachea and respiratory system called?
A
Lung bud
21
Q
What is the septum that develops between the esophagu and the trachea?
A
Tracheo-esophageal septum
22
Q
When in development does the trachea/esophagus form?
A
4th week
23
Q
What happens if there is a short esophagus?
A
Pulls the stomach into the thoracic cavity
24
Q
What happens to the esophagus lumen as growth continues?
A
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
