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Microanatomy > GI Embryology > Flashcards

GI Embryology Flashcards

1
Q

Arteries and Gut Regions

A
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2
Q

Foregut

A

Esophagus

Stomach

Duodenum

Liver

Pancreas

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3
Q

Hindgut

A

Colon

Rectum

Anal Canal

Sigmoid

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4
Q

Midgut

A

Duodenum

Jejunum

Ileum

Colon

Cecum

Appendix

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5
Q

Pharyngeal Gut

A

Oral Cavity

Pharynx

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6
Q

Embryo Dev

A

Week 3 & 4 folding occurs into 3 disc layer

Endodermal lined gut tube connected to vitelline duct

Buccopharyngeal m. breaks down week 4 to form mouth= stomodeum

Cloacal m. ruptures in 7th week, creats opening for anus and urethra

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7
Q

Mesenteries

A

2x peritoneum that enclose organ & connect it to body wall

Peritoneaum simple squamous epith that secretes mucus and lines abdominal cavity

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8
Q

Dorsal Mesentary

A

extends from lower end of esophagus to cloacal region of hindgut.

Moditifed during dev to become:

Dorsal mesogastrium

mesoduodenum

proper

mesocolon

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9
Q

Ventral Mesentery

A

only in terminal esophagus, stomach & upper duodenum

Modified during development to become lesser omentum & falciform ligament.

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10
Q

Mucosa

A

Epithelial lining & glands (from endoderm)

Lamina propria

Muscularis mucosae

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11
Q

Splanchnic Mesoderm

A

Submucosa

Muscularis externa

Adventitia/serosa

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12
Q

Foregut Expanded

A

Esophagus- week 4 respiratory diverticulum is outgrowth from primitive gut tube.

Located caudal to primitive pharynx

Separated from dorsal part of foregut by tracheoesoph septum eventually.

Esophageal segment grows & eleongates during 2nd month.

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13
Q

Esophageal Atresia

A

Results from deviaton of tracheoesophageal septum in posterior direction associated w/ polyhydraminios

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14
Q

Short Esophagus

A

Failure of esophagus to elongate in proportion to dev of neck & thora.

Results in stomach being displaced cranially into thorax forming congenital hiatal hernia.

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15
Q

Stomach Dev

A

4TH week, dilation in foregut occurs

dorsal border grows fater than ventral border which yeild lesser & greater curvatures

Stomach develops in midline then rotates 90 CW then CCW

R & L vagus innervate post & ant walls

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16
Q

Omental Bursa

A

dorsal mesogastrim continues to expand during dev as 2x layered sac over both small intestines & transverse colon

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17
Q

Congenital Pyloric Stenosis

A

5x more common in males than in females

Hypertrophy of m. layer in pyloric region of stomach

After feeding stomach is distended= projectile vomiting!

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18
Q

Spleen Formation

A

Not foregut

Mesodermal origin- b/t layers of dorsal mesentery

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19
Q

Duodenum Formation

A

Week 4, distal foregut & proximal midgut join to form C shaped tube

Stomach rotation brings duodenum ultimately to lie on R side of abdominal cavity

Duodenum & pancrease head pressed dorsally against body wall.

R surface of dorsal mesoduodenum fuses with peritoneum.

Retroperitoneal position

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20
Q

Duodenal Formation 2

A

During 2nd month, duodenum epithelial proliferation, obliteration of lumen & recanalization

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21
Q

Duodenal Stenosis & Atresia

A

Stenosis partial occlusion of lumen due to incomplete recanalization of duodenum

Foreceful vomiting like in pyloric stenosis

Duodenal atresia complete closure of lumen & results in polyhydraminos

22
Q

Liver & Gallbladder Development

A

Glands of GT formed by complex interaction b/t endodermal outpocketings of primitive gut tube & surrounding mesenchyme (mesoderm)

*Use SHH & HOX

23
Q

Liver Bud

A

End of 3rd or beginning of 4th week, liver bud appears out of foregut

Caudal portion of liver bud differentiates into bile duct

overgrowth from bile duct gives rise to gallbladder & cystic duct.

As growth continues, liver bud extends into septum trasnversum

24
Q

Septum Transversum

A

Plate of splanchnic mesoderm lies b/t thoracic cavity & stalk of yolk sac. Appears on day 22

Ultimately becomes: central tendon of diaphragm & ventral mesentery

Hepatic cords (foregut endoderm) diff into hepatocytes & lining of biliary ducts

Umbilical & vitelline v.–> hepatic sinusoids

CT, hematopoietic tissue & Kupffer cells derived from mesoderm of septum transversum

25
Bare A of Liver
Mesoderm on surface of liver fomrs visceral peritoneum of liver, except A where it lies in contact with diaphragm (bare A of liver)
26
Functions of Developing Liver
Hematopoiesis- 5 to 6 week Bile production- 12th week, bile drains down newly fomred bile duct & stored in intestines. As bile released into intestines it gives meconium its characteristic green color
27
Gallbladder & Extrahepatic Duct Development
Bile Duct- narrow channel b/t liver bud & foregut Gllbladder & cystic duct- formed from outgrowth of bile duct gallbladder also undergoes mitosis whereby lumen is obliterated
28
Accessory Hepatic ducts & duplication of gallbladder
Also extrahepatic biliary atresia Intrahepatic biliary atresia- from maternal infection
29
Pancreas Formation
In 5th week Two buds originating from endodermal lining of duodenum Duodenum rotates 90 CW, the ventral bud carried dorsally (along with bile duct), eventually located posterior to dorsal bud. 2 buds fuse in 6th week Dorsal bud- head, body & tail Ventral bud- uncinate process
30
Exocrine and Endocrine Pancreas
Exocrine- none Endocrine- Islets of Langerhan start to develop in 3rd month. A cells diff first, followed by B cells or D cells Not known when F cells are formed. Glucagon first detected in fetal plasma by 15th week, insulin in 5th month.
31
Ectopic Pancreatic Tissue
Can be found anywhere from distal esoph to tip of primary intestinal loop Most freq in duodenum or mucosa of stomach 5% Meckel's Diverticulum contains pancreatic tissue
32
Annular Pancreas
2 portions of ventral bud rotates in opp direction & encircle the duodenum from both sides
33
Midgut Dev
Midgut rapidly expands in 5th week resulting in fomraiton of U shaped loop Same time as primary intestinal loop rotates 90 CCW around an axis formed by SMA
34
Physiological Herniation
In 6th week all intestinal loops enter extraembryonic cavity in umbilical cord Due to rapid growth of cephalic limb Expansion of liver
35
Retraction of Herniated Loops
In 10th week, intestine re enter abdominal cavity As it returns it undergo a further 180 CCW rotation Due to regression of 2nd kidnye sys, reduced growth of liver, expansion of abdominal cavity During dev midgut undergoest 270 degree CCW rotation!
36
Fixation of Intestines
Mesenteries of ascend & descend colon are fixed against peritoneum & later fuse, therefore they become retroperitoneal. Transverse mesocolon fuses w/ post wall of greater omentum, maintainign its mobility
37
Atresia or stenosis of gut
would cause considerable backup in gut leading to excessive GI distension & excessive vomiting in newborns. Most commonly caused by vascular accidents
38
Apple Peel Atresia
10% of bowel atresia, occurs in jejunum
39
Recanalization
40
Omphalocele
Failure of return of intestinal loop into body cavity after phys herniation 6-10 weeks Associated w/ high rate mortality, sever cardiac & NTDs & chrom abnormalityes
41
Gastroschisis
Herniation of abdominal contents through defect in abdominal wall directly into amniotic cavity. Not covered by amnion & peritoneaum, occurs lateral to the umbiliucs Not associated w chrom abnormalites or othere severe defects. Excellent survival rates. \*ventral wall defect\*
42
Vitelline Duct Abnormalities
As intestines reenter abdomen, vitelline duct obliterated Except: Remnant of vitelline duct, may contain ectopic pancreatic or gastric tissue
43
Abnormal Rotation
44
Hindgut Dev
In embryonic period of cloaca is subdivided into anorectal canal (post) & urogenital sinus (ant) Accomplished by means of urorectal septum.
45
Anal Canal
Upper 2/3 formed from anorectal canal (hindgut) Lower 1/3 formed from invagination of ectoderm Junction is known as pectinate line. At pectinate line epith undergoes a sudden transition from simple columnar to stratified squamous. BV: cranial portion- sup rectal a. Caudal portion- inf rectal a.
46
Imperforate Anus
No anal opening, lack of recanalization of anal canal, failure of anal mem to break down .
47
Rectoanal Atresia & fistula
ectopic positioning of anal opening, due to incomplete separation of anorectal canal from urogenital sinus
48
Differentiation
Primite gut diff into diff organs depending on reciprocal inteaction b/t endoderm & mesoderm. Mesoderm HOX dictates type of structure that will fomr Endoderm SHH induces HOX expression in mesoderm
49
Appendix
50
Anal Canal
Upper 2/3= simple columnar Lower 1/3= stratified squamous non keratinized Anus- stratified sqamous keratinized of skin
51
Anal Canal Sphincters
Internal Anal sphincter- thickened inner layer of muscularis externa External anal sphincter- skeletal m.

Microanatomy (9 decks)

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