GI Glands

Question 1

describe the fxn of liver

Answer 1

• produces and secretes most of circulating plasma proteins
  
  • albumins
  • lipoproteins (VLDL)
  • glycoproteins (haptoglobulin, transferrin)
  • prothrombin
  • non0immune alpha and beta gloublins
• storage and/or conversion of vitamins (A,D,K) and iron
• degrades drugs and toxins via conjugation and oxidation

Question 2

describe Glisson’s capsule

Answer 2

• fibrous CT encloses and subdivides the liver into lobes and lobules
• capsule surrounded by visceral peritoneum except where liver attached to other structures
• Glissons capsule is covered by the mesothelial lining of the peritoneum making the liver intraperitoneal

Question 3

Answer 3

Question 4

describe the porta hepatis

Answer 4

• the region where the main hepatic artery and the portal vein enter and the hepatic ducts leave the liver
• separates quadrate and caudate lobes of liver
• contrast with portal canal which contains branches of these vessels and found between 2 lobules

Question 5

describe the blood supply of the liver

Answer 5

• vascular components of the porta hepatis
• hepatic artery (25%) = fully oxygenated
• portal veins (75%) = venous blood from intestines, pancreas and spleen
  
  • rich in nutrients, endocrine secretions and blood cell breakdown products

Question 6

describe the venous drainage of the liver

Answer 6

• hepatic vein drains most of the blood from the liver
  
  • formed by the union of numerous sublobular veins
• sublobular veins collect blood from the central vein of each class liver lobule

Question 7

describe hepatic sinusoids

Answer 7

• discontinuous endothelium
  
  • numerous large fenestrations without diaphragm
  • gaps between endothelial cells
  • associated with Kupffer cells (macrophages), which are phagocytic cells from the monocyte lineage

Question 8

Answer 8

Question 9

describe hepatocytes

Answer 9

• microvilli on surface of cell
• foamy appearance of cytoplasm due to glycogen
• lipofuscin granules

Question 10

describe the surfaces of the hepatocyte

Answer 10

• adjacent neighboring hepatocytes (green)
  
  • form small, tunnel-like bile canaliculi that are special intercellular spaces
  • TJs between the hepatocytes
  • microvilli extend into the bile canaliculus from each hepatocyte
• adjacent space of Disse (red)
  
  • microvilli assist in the transfer of material to and from hepatocytes
    
    • this is where the endocrine secretion of the liver also takes place

Question 11

Answer 11

green = adjacent neighboring hepatocyte

red = space of Disse

Question 12

describe the peri-sinusoidal space (aka the space of Disse)

Answer 12

• it is the subendothelial space between the liver cells and the lining cells of the sinusoids
• basal lamina is not present in this space
• function:
  
  • exchange of material b/t the bloodstream and the hepatocytes (which do not contact the bloodstream)
    
    • therefore the adjacent liver surface is specialized for its endocrine functions
• reticular fibers help maintain the architecture of sinusoids
• un-myelinated nerve fibers
• short, blunt microvilli of hepatocytes

Question 13

what type of cells are found in the perisinusoidal space (of Disse)?

Answer 13

• stellate-shaped fat storing cells called Ito cells (which preferentially store vit. A)
  
  • in cirrhosis they play a significant role in fibrogenesis and subsequent portal hypertension

Question 14

Answer 14

Question 15

describe bile canaliculi

Answer 15

• receive the exocrine secretion of the liver (bile) thus representing the beginning of the duct system
• initial site of biliary tree
• convey bile to canals of Herring which then drain into the bile ductule

Question 16

describe biliary tree

Answer 16

• consist of the bile canaliculi (lined by hepatocytes) which travels to:
• canals of Herring (lined by both cuboidal cholangiocytes and hepatocytes), which travel to:
• intrahepatic bile ductules (found in the peri-portal space of Mall and lined by only cuboidal cholangiocytes) which drains into:
• interlobular bile (hepatic) ducts found in the portal triad
• main difference between Canal of Herring and the bile ductule is whether it is completely or partially lined by cholangiocytes

Question 17

describe non-alcoholic fatty liver

Answer 17

• fat deposits in the liver without a history of alcohol abuse
• lipid filled cytoplasmic vacuoles very similar to alcoholic fatty liver disease
• associated with obesity, insulin resistance
• most severe form is non-alcoholic steatohepatitis (NASH)
  
  • cirrhosis
  • hepatocellular cancer

Question 18

describe liver chirrhosis

Answer 18

• changes due to chronic alcohol intake:
  
  • parenchymal injury and consequent fibrosis are diffuse, extending through the liver
  • fibrosis is irreversible
• mechanism:
  
  • collagen is deposited in all portions of the lobule
  • alterations in the sinusoidal endothelial cells
• net result is severe blood flow disruption and decrease in hepatocyte function
• nodular appearance is due to extensive fibrosis surrounding nodular clusters of healing hepatic tissue

Question 19

describe the hepatobiliary tree

Answer 19

• interlobular ducts -> R and L hepatic ducts -> common hepatic duct -> cystic duct which leads to the gallbladder
• the common bile duct delivers its content into the lumen of the duodenum via the ampulla of vater after joining with the main pancreatic duct

Question 20

describe the sphincter of Oddi

Answer 20

• proximal to the ampulla of Vater
• formed thickening of the muscularis externa of the duodenum at the ampulla
• regulates the flow of bile and pancreatic juice into the duodenum

Question 21

describe the gallbladder

Answer 21

• small, pear-shaped organ
• stores and concentrates bile manufactured by liver
  
  • stores 40-60 mL
• muscle wall contracts to force the bile in its lumen into the duodenum where the bile acts to emulsify fats
  
  • contraction is facilitated by hormone cholecystokinin (secreted by enteroendocrine cells)

Question 22

describe the epithelium of the gallbladder

Answer 22

• simple columnar epithelium
• apical microvilli
• junctional complexes at apical surface which form a barrier between the lumen and the intercellular compartment
• mitochondria at basal surface

Question 23

describe the lamina propria and the muscle layer of the gallbladder

Answer 23

• lamina propria
  
  • abundant fenestrated capillaries
  • highly convoluted in empty gallbladder
  • mucous glands proximal to the cystic duct -> abundant in cholecystis
• muscle layer
  
  • think layer of smooth muscle cells oriented in an olbique fashion

Question 24

describe the CT covering of the gallbladder

Answer 24

• dense, irregular collagenous, with nerves and blood vessels

Question 25

describe cholelithiasis (gallstones)

Answer 25

• 80% of stones are cholesterol stones
• risk factors = 4 Fs
  
  • advancing age (>40s)
  • females
  • fat
  • fertile
• clinical presentation:
  
  • symptomatic only if there is blockage

Question 26

describe serous cells

Answer 26

• pyramidal shape
• protein secreting cells
• spherical nucleus
• large amounts of rER, free ribosomes, prominient Olgi
• zymogens at the apical zone with basal or perinuclear organelles
  
  • hence basal basophilia and apical eosinophilia

Question 27

describe mucus cells

Answer 27

• mucin secreing cells
• nucleus flattened at base of cell
• mucinogen granules and large Golgi apparatus apically located
• appears “frothy” and stains weakly with H&E

Question 28

describe intralobular ducts

Answer 28

• intercalated ducts
  
  • smallest ducts
  • lined by low cuboidal epi.
  • secrete bicarb
• striated ducts
  
  • high cuboidal to columnar lining
  • contain abundant mt in the basal in-foldings
  • reabsorb more Na from primary secretion

Question 29

describe the parotid gland

Answer 29

• pure serous, compound, tubuloalveolar gland
• capsule: formed by the superficial cervical fascia -> collagenous
• secretory portion consists of serous amylase-producing cells that store this enzyme in granules
  
  • granules also contain peroxidase, lysozyme and cytstatins

Question 30

Answer 30

Question 31

describe an excretory duct

Answer 31

• travel in the interlobular and interlobar CT
• epithelium changes from simple columnar to stratified cuboidal/columnar and then turn into stratified squamous epithelium of oral cavity

Question 32

describe Stensen’s duct

Answer 32

• largest excretory duct of the parotid gland

Question 33

describe sublingual gland

Answer 33

• mixed, compound tubuloalveolar gland
• mostly mixed units with serous demilunes
  
  • purely serous units are not present