Histology of the Paraalimtary Tract Flashcards
About how many liters of fluid do we secrete from the paraalimentary tract each day?
About 4L. (2L from the pancreas, 1L from each the liver and salivary glands)
4 things that salivary glands secretion?
Digestive enzymes - salivary amylase.
Proteins etc. to maintain enamel.
Lysozymes - prevent bacterial overgrowth.
IgA
What do the duct cells of salivary glands look like?
They have myoepithelial cells and striations.
How do serous and mucous-secreting cells appear different?
Serous - cuboidal, more pink.
Mucinous - they look like the secrete mucus… more blue.
Are the islet (endocrine) and exocrine parts of the pancreas from different embryological origin? Relevance?
No - they’re from the same origin. (contrast with eg. adrenal cortex and medulla)
You can get tumors with mixed endocrine and exocrine phenotypes.
Which cells in the pancreas secrete bicarb?
Duct epithelial cells (not the acini).
duct epithelial cells also secrete mucins
How does the pancreas protect itself from digestive enzymes? (3 ways)
Most enzymes are made as inactive pro-enzymes.
Zymogen granules package them.
Secretion is into the lumen, and cells are protected by tight junctions.
(next lecture also mentions anti-trypsins)
4 liver functions? (big oversimplification)
Detoxification
Hormone converter (Vit D, T4->T3)
Storage
Synthesis
What molecule, produced by amino acid breakdown, is particularly important for the liver to clear as part of normal metabolism?
Ammonia - using glutamate and transaminases… and also made into urea.
What part of the liver can sense pain?
The capsule - it hurts when stretched.
4 compartment of liver blood flow?
Portal tract
Limiting plate
Cords (with fenestrated endothelium)
Terminal venules
Hepatocytes regenerate.
Yeah. Mitosis.
Where there should be collagen in the liver, normally?
Around the portal tract, a little bit around the central vein.
Not in the sinusoids, as this would impair exchange.
Does collagen in the liver just play a structural role?
Nope, it also plays a signaling role…. of some kind.
How is the collagen structure in the liver different from normal?
It stays in more of a gel… not organized into fibers.
What is “bile” composed of?
Conjugated bilirubin + bile salts.
What is the difference between conjugated and unconjugated bilirubin?
Bilirubin has glucuronide added to it in hepatocytes to make it water soluble.
Can you normally see bile canaliculi in liver H&E histology?
No, not without a special stain.
If you can see them, their probably distended due to bile blockage.
Where is GGT, subcellularly?
The apical bile canaliculus.
Where is ALT, subcellulary?
In the hepatocyte cytoplasm.
Where is AST, subcellularly?
In both the mitochondria and cytoplasm of the hepatocyte.
What are the “zones” of the liver based upon?
Which hepatocytes see incoming blood first.
Zone 1 is nearest the portal tracts, and sees incoming blood first. Zone 3 is closest to the central veins.
Which liver zone is most susceptible to ischemic injury?
Zone 3
What the signal for the gall bladder to contract and release bile?
CCK
What special ability does the gall bladder have? (that other parts of the gut / paraalimentary tract can’t do… except the saliva glands)
It has the ability to concentrate - it concentrates bile.
How do the tissue layers differ in the gall bladder?
There’s no muscularis mucoase (the lamina propria is continuous with the submucosa). The circular and longitudinal layers of the muscularis propria aren’t distinct.
