LEC 24: Abdomen I

Question 1

What are the organs of the digestive tube

Answer 1

• mouth
• pharynx and esophagus
• stomach
• small intestine (duodenum, jejunum, ileum)
• large intestine (cecum, colon, rectum, anal canal, anus)

Question 2

What are the accessory organs of the digestive tract

Answer 2

• teeth
• salivary glands
• liver
• pancreas

Question 3

When does the primordial gut begin

Answer 3

Week 4

• FGF signal A-P axial patterning
• signals for induction of endoderm
  
  • FGF4 and activins
• Endoderm: specifies temporal and positional information
• stomodeum, proctodeum

Question 4

What are the 5 classes of foregut derivatives

Answer 4

• primordial pharynx and derivatives
• lower respiratory system
• esophagus and stomach
• duodenum–PROXIMAL to bile duct
• liver, billiary apparatus, pancreas

Question 5

Where does the esophagus and stomach derive from

Answer 5

foregut

Question 6

Where do the oral cavity, pharynx, tongue, tonsils, salivary glands, upper respiratory system derive from

Answer 6

foregut (primordial pharynx and derivatives)

Question 7

Where does the duodenum derive from

Answer 7

foregut

Question 8

Where do the liver, billiary apparatus, and pancreas derive from

Answer 8

foregut

Question 9

Development of esophagus

Answer 9

• T-E suptum separates esophagus
• epithelium obliterates lumen and then it is recanalized
• Upper 1/3: striated muscles from pharyngeal arches
  
  • move food down
• Lower 1/3: smooth muscle from surrounding splanchnic mesenchyme
• Cranial Nerve X (VAGUS)

Question 10

What innervates the esophagus and what is the main supplier of blood flow

Answer 10

• Cranial Nerve X (Vagus) innervates the esophagus
• Celiac trunk is the primary blood supply to the esophagus

Question 11

esophageal stenosis

Answer 11

• incomplete recanalization of esophagus during 8th week

OR

• failure of esophageal blood vessels to develop (atropy–lack of developing tissue causes dying)

Question 12

When does the development of the stomach occur

Answer 12

Stomach development happens in week 4

Question 13

Stomach development

Answer 13

• dilation of tubular structure
• fusiform enlargment
• initially oriented in median plane
• during weeks 4-6, broadens ventro-dorsally
  
  • dorsal boder grows faster, greater curvature forms
  • greater curvature toward vertebral column
  • lesser curvature towards anterior abdominal wall
  • surfaces are still left/right oriented

Question 14

Rotation of stomach

Answer 14

• Stomach, situated in median plane with greater curvature towards dorsal surface, lesser curvature toward ventral surface
• rotates 90 degrees in a clockwise direction
  
  • ​lesser curvature (ventral border) moves right
  • greater curvature (dorsal border) moves left
  • original left side now ventral surface
  • original right side now dorsal surface

Question 15

What nerves supply the walls of the stomach

Answer 15

LEFT VAGUS

• supplies anterior wall

RIGHT VAGUS

• supplies posterior wall

Question 16

How is the stomach suspended in the abdomen

Answer 16

The stomach is suspended by dorsal mesogastrium (originally in median plane)

• mesentary carried to the left during rotating
• this forms omental bursa

Question 17

omental bursa

Answer 17

• clefts in dorsal mesogastrium coalesce to form omental bursa
• with rotation, it is pulled to the left and stretched
• allows free movement of stomach

Question 18

ventral mesogastrium

Answer 18

• dorsal mesogastrium forms the omental bursa
• ventral mesogastrium suspends the stomach and duodenum to liver and ventral abdominal wall

Question 19

What are the recesses formed by the dorsal mesogastrium

Answer 19

• dorsal mesogastrium elongates to become the greater omentum
• inferior recess disappears when layers fuse

Question 20

Congenital Pyloric Stenosis

Answer 20

• 3/1000
  
  • males>females
• stenosis of pyloric canal
• obstruction of food
• projectile vomiting

Question 21

What is the duodenum derived from

Answer 21

Duodenum has a dual origin and dual blood supply

FOREGUT

• proximal to level of bile duct
• blood supplied by celiac trunk

MIDGUT

• blood supplied by superior mesenteric artery

Question 22

What is the blood supply to the duodenum

Answer 22

Duodenum derives from foregut (proximal to bile duct) and midgut

• celiac artery supplies the foregut derived portion
• superior mesenteric artery supplies midgut derived portion

Question 23

How does the duodenum rotate

Answer 23

• duodenal loop projects ventral
• with rotation, moves rightward
• the lumen becomes obliterated and then recanalizes during weeks 5-6

Question 24

duodenal stenosis

Answer 24

• partial occlusion of the lumen
• due to incomplete recanalization from defective vacuolization
• stomach contents (with bile) are vomited

Question 25

duodenal atresia

Answer 25

* complete occlusion of duodenum * 20-30% associated with Down Syndrome * segment without recanalization * can happen in multiple sections of duodenum * "double-bubble" sign -- polyhydramnios * backed up dilated duodenum because of atretic segment

Question 26

liver, gallbladder, and biliary apparatus

Answer 26

* during week 4, outgrowth in foregut * Fibroblast growth factors (FGF) from heart --\> bipotential cells --\> hepatic diverticulum * hepatic diverticulum extends into septum transversum (from early embryo folding) * hepatic diverticulum divides into 2 parts * endodermal cells --\> hepatic cords --\> sinusoids * mesenchyme in septum transversum --\> kupffer cells and hematopoetic tissue

Question 27

function of the gallbladder

Answer 27

emulsifies fatty foods

Question 28

Kupffer cells

Answer 28

macrophages derived from mesenchyme in septum transversum (get rid of bacteria)

Question 29

hematopoetic tissue

Answer 29

derived from mesenchyme in septum transversum (important for the formation of blood cells)

Question 30

significance of liver formation

Answer 30

* right lobe is larger * hematopoiesis (begins around week 6) * bile formation (begins at week 12)

Question 31

What is the gallbladder formed from

Answer 31

small part of hepatic diverticulum forms the gallbladder

Question 32

What is the cystic duct formed from

Answer 32

stalk of diverticulum

Question 33

role of bile duct

Answer 33

connects hepatic and cystic ducts to duodenum

Question 34

Where is the entrance of the common bile duct

Answer 34

common bile duct moves posteriorly with stomach rotation

Question 35

ventral mesentary

Answer 35

* lesser omentum * hepatogastric ligament * heaptoduodenal ligament * falciform ligament * forms visceral peritoneum of liver

Question 36

accessory hepatic ducts

Answer 36

* extrahepatic biliary atresia * 1:10,000 to 1:15,000 * failure of ducts to canalize or fetal infection

Question 37

development of pancreas

Answer 37

* caudal foregut endodermal cells--\>pancreatic buds (dorsal to ventral) * rotation of stomach, duodenum leads to pancreas lying on dorsal abdominal wall * ducts fuse to form main pancreatic duct * **exocrine:** endodermal tubules branch to form acinar cells and ducts * **endocrine:** clumps of cells from exocrine part form islets

Question 38

annular pancreas

Answer 38

* growth of bifid ventral pancreatic bud around duodenum * can cause duodenal obstruction

Question 39

Where does the spleen develop from

Answer 39

* spleen develops from mesenchyme in dorsal mesogastrium * thickening of mesoderm in dorsal mesogastrium * mesenchymal cells differentiate * capsule, connective tissue, parenchyma * center for hematopoiesis

Question 40

accessory spleen

Answer 40

* 10% of population * tail of pancreas is a gastrosplenic ligament