Histology of the Paraalimtary Tract

Question 1

About how many liters of fluid do we secrete from the paraalimentary tract each day?

Answer 1

About 4L. (2L from the pancreas, 1L from each the liver and salivary glands)

Question 2

4 things that salivary glands secretion?

Answer 2

Digestive enzymes - salivary amylase.
Proteins etc. to maintain enamel.
Lysozymes - prevent bacterial overgrowth.
IgA

Question 3

What do the duct cells of salivary glands look like?

Answer 3

They have myoepithelial cells and striations.

Question 4

How do serous and mucous-secreting cells appear different?

Answer 4

Serous - cuboidal, more pink.

Mucinous - they look like the secrete mucus… more blue.

Question 5

Are the islet (endocrine) and exocrine parts of the pancreas from different embryological origin? Relevance?

Answer 5

No - they’re from the same origin. (contrast with eg. adrenal cortex and medulla)
You can get tumors with mixed endocrine and exocrine phenotypes.

Question 6

Which cells in the pancreas secrete bicarb?

Answer 6

Duct epithelial cells (not the acini).

duct epithelial cells also secrete mucins

Question 7

How does the pancreas protect itself from digestive enzymes? (3 ways)

Answer 7

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)

Question 8

4 liver functions? (big oversimplification)

Answer 8

Detoxification
Hormone converter (Vit D, T4->T3)
Storage
Synthesis

Question 9

What molecule, produced by amino acid breakdown, is particularly important for the liver to clear as part of normal metabolism?

Answer 9

Ammonia - using glutamate and transaminases… and also made into urea.

Question 10

What part of the liver can sense pain?

Answer 10

The capsule - it hurts when stretched.

Question 11

4 compartment of liver blood flow?

Answer 11

Portal tract
Limiting plate
Cords (with fenestrated endothelium)
Terminal venules

Question 12

Hepatocytes regenerate.

Answer 12

Yeah. Mitosis.

Question 13

Where there should be collagen in the liver, normally?

Answer 13

Around the portal tract, a little bit around the central vein.
Not in the sinusoids, as this would impair exchange.

Question 14

Does collagen in the liver just play a structural role?

Answer 14

Nope, it also plays a signaling role…. of some kind.

Question 15

How is the collagen structure in the liver different from normal?

Answer 15

It stays in more of a gel… not organized into fibers.

Question 16

What is “bile” composed of?

Answer 16

Conjugated bilirubin + bile salts.

Question 17

What is the difference between conjugated and unconjugated bilirubin?

Answer 17

Bilirubin has glucuronide added to it in hepatocytes to make it water soluble.

Question 18

Can you normally see bile canaliculi in liver H&E histology?

Answer 18

No, not without a special stain.

If you can see them, their probably distended due to bile blockage.

Question 19

Where is GGT, subcellularly?

Answer 19

The apical bile canaliculus.

Question 20

Where is ALT, subcellulary?

Answer 20

In the hepatocyte cytoplasm.

Question 21

Where is AST, subcellularly?

Answer 21

In both the mitochondria and cytoplasm of the hepatocyte.

Question 22

What are the “zones” of the liver based upon?

Answer 22

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.

Question 23

Which liver zone is most susceptible to ischemic injury?

Answer 23

Zone 3

Question 24

What the signal for the gall bladder to contract and release bile?

Answer 24

CCK

Question 25

What special ability does the gall bladder have? (that other parts of the gut / paraalimentary tract can’t do… except the saliva glands)

Answer 25

It has the ability to concentrate - it concentrates bile.

Question 26

How do the tissue layers differ in the gall bladder?

Answer 26

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.