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Flashcards in Ward I Deck (56)
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Describe the flow of pancreatic secretions.

Pancreatic secretions flow into larger intralobular ducts & into the main pancreatic duct-->duodenum


What are the 4 types of pancreatic secretions?

proteolytic enzymes
carbohydrate enzyme
pancreatic lipase
cholesterol esterase


What are examples of proteolytic enzymes?

Tyrpsin, chymotrypsin, carboxypolypeptidase


What is the main carbohydrate enzyme & what does it do?

pancreatic amylase: breaks glycogen, starch & carbs into di & trisaccharides


What does pancreatic lipase do?

hydrolyzes neutral fat to fatty acids & monoglycerides


What does cholesterol esterase do?

hydrolyzes cholesterol esterases & phospholipases so that fatty acids can be separated from phospholipids


How do you activate trypsinogen?

enterokinase (released from mucosa when it contacts chyme)


How do you activate chymotrypsinogen?



What is the purpose of the trypsin inhibitor?

it is released from glandular cells in the pancreas & prevents the trypsinogen from being activated in the secretory cells, acini or pancreatic duct...otherwise it would eat the pancreas! Sad.


What happens in the pancreatic acinar cell?

protein synthesis happens in the RER.
proteins are collected in the cisternal cavity
the enzymes are condensed into vacuoles
there they are concentrated into zymogen granules
the zymogen granules fuse w/ the apical membrane & rupture to release their contents


Where are bicarb ions & water secreted from in the pancreas?

from the epithelial cells of the ducts of the acini
**when stimulated to release zymogen granules, also releases the bicarb & water


How do the conc'n of the ions in this secretion compare to that of plasma? What pH is created by the bicarb ions?

Na+ & K+ similar to plasma
Cl- less than plamsa
HCO3- produces a pH of 8.2


What are the 2 proposed mechanisms for how bicarb is secreted?

I. Acinar cells secrete stuff w/ Na+ & K+ & the duct cells secrete stuff w/ a ton of bicarb.
II. Acinar cells secrete stuff rich in bicarb. Duct cells exchange the bicarb for Cl-. When flow is fast, less bicarb can be exchanged.


What is HCO3- secretion from duct cells dependent on?

the amount of luminal Cl- ions to exchange with!!
exchanger on the apical membrane
HCO3- made by CA from the CO2 diffused from blood


What are the 4 basic stimuli that are critical in determining pancreatic secretions?



When is ACh released?

from parasympathetic vagal nerve terminals & from other cholinergic nerves in the enteric nervous system


When is gastrin released?

it is released during the gastric phase of the stomach


When is CCK released?

when food enters the SI...it is released from the duodenal mucosa


When is secretin released?

secreted when low pH products enter the SI


Which of the stimuli cause the pancreatic acinar cells to prepare the digestive enzymes?

**but no fluid secretion!!


What does secretin do?

Thankfully, secretin stimulates large secretions of bicarb soln from ductal cells in the pancreas, but doesn't affect enzyme secretions.


During the cephalic phase of digestion...what is released? Does this cause pancreatic enzyme secretion?

ACh released @ pancreas. Causes enzymes to be secreted in acini. But NO real secretions b/c of lack of fluid to flow that stuff thru the duct.


During the gastric phase of digestion...what is released? Does this cause pancreatic enzyme secretion?

Gastrin released
There still aren't really secretions from the pancreas b/c of the lack of fluid...


During the intestinal phase of digestion...what is released? Does this cause pancreatic enzyme secretion?

Secretin & CCK are released...
This is stimulated by the chyme when it enters the duodenum...
These 2 substances travel in the blood & stimulate the pancreas to secrete enzymes. With the secretin stimulating the duct cells to release bicarb & water...it can actually flow into the SI.


Let's focus in on secretin release. What cells release it? What 2 substances really stimulate its release? What pH makes it ideal to release? What 2 things potentiate its release?

Secretin is released from S cells. HCl/Gastric acid & long chain fatty acids stimulate this release. The HCl creates a lower pH...when it gets to like 4.5 secretin is released. CCK & ACh potentiate the release of secretin.


Let's focus in on CCK. What cells release it? What 2 things prompt its release?

I cells in the duodenal mucosa & upper jejunal mucosa release it.
Proteoses & peptones prompt its release. These are products of long chain fatty acid digestion.


The bicarb released in the duodenum is a part of a protective mechanism to get rid of extra HCl. This protects the intestinal mucosa from being destroyed! Describe this mechanism.

HCl + NaHCO3- --> NaCl + H2CO3 -->H2O + CO2
The CO2 is absorbed in the blood & expired in the lungs. This gets rid of extra acid.


Aside from a protective mechanism...what else does bicarb do in the SI that's awesome?

The HCO3- raises the pH of the lumen to around 8. This is ideal for the function of pancreatic enzymes.


What are the 2 main functions of bile?

1. emulsify large fat particles into small fat particles that can be broken down by pancreatic lipases. Furthermore, bile salts help transport these break down products thru the SI mucosa.
2. helps w/ excretion of waste products from the blood (like bilirubin & excess cholesterol)


T/F Bile consists of both organic & inorganic compounds.