GI Physiology 4 Flashcards
Pancreatic secretions have what roles
Protective roles - HCO3 and mucus
Digestive roles - Enzymes
Cells of the pancreas include
Acinar cells
Duct cells
Goblet cells
Cells of the pancreas - Acinar cells
Protein synthesizing cell
Secretion of digestive enzymes
Secrete fluid
Cells of the pancreas - Duct cells
HCO3 secretion (important protective role)
Ion transport
Fluid transport
Cells of the pancreas - Goblet cells
Mucin secretion
- lubricates, hydrates, protects, and gives immune function
Pancreatic digestive enzymes - Inactive includes (one important one)
Trypsinogen
Pancreatic digestive enzymes - Active includes (4 important ones)
Alpha amylase
Lipase
Colipase
Trypsin inhibitor
Pancreatic digestive enzymes - Trypsinogen Function
INACTIVE
Functions in protein digestion
We do not want to initiate protein digestion in the pancreas (we want to wait until duodenum)
Pancreatic digestive enzymes - Alpha amylase Function
ACTIVE
Carb digestion
Pancreatic digestive enzymes - Lipase Function
ACTIVE
Lipid digestion
Pancreatic digestive enzymes - Colipase Function
ACTIVE
Lipid digestion
Pancreatic digestive enzymes - Trypsin Inhibitor
Inhibits trypsin
If we do not inhibit trypsin and protein digestion starts in pancreas, damage will occur
Stimulation of enzyme and fluid secretion - Key stimuli for secretion of fluid and enzymes
CCK and Ach
They promote Ca influx and promote docking of enzymes containing vesicles at the apical membrane
As you inc conc of CCK, you get inc in release of the enzymes
Multiple roles of CCK in the pancreas to include
CCK acts on the pancreas with reduces gastric emptying and stimulates acinar cells
Protection against and activation of digestive enzymes
Secretions of the pancreas can be very destructive so many of the digestive enzymes are inactive
Vesicles contain trypsin inhibitor
Low pH of vesicle prevents enzyme activation
How do we protect pancreas from its own secretions?
By making the proteases in the inactive form and keep the pH low in the vesicles
Trypsin inhibitor is there too just in case
Activation of enzymes in the____
DUODENUM
The on switch is located in the duodenum
When the enzymes empty into the duodenum, Entero Peptidase converts trypsinogen to trypsin and once you have a few molecules of trypsin they can go on to activate the other proteases
Duodenal Protection - Pancreas also functions to protect the
duodenum from the acid being emptied from the stomach to the duodenum
Duodenal protection - how does the pancreas protect it?
Acid come in, the duodenum senses it and releases secretin which stimulates the pancreatic ducts to release HCO3 which is important in protection
When you hear secretin think
GI PROTECTION
Duodenal protection - Negative regulation of acid secretion by secretin
Inc release of somatostatin
Dec gastrin secretion
Dec proton pump expression
Phase of pancreatic secretion - interdigestive - Pancreatic secretions during the interdigestive period parallel the _______
Therefore _____
Secretion is highest during ____
migrating motor complexes
Therefore, pancreatic secretions parallel motility
Secretion is highest during intestinal contractility
Phase of pancreatic secretion - interdigestive - Regulators of the cyclical pattern include
Stimulation by the PNS and CCK
Inhibition by alpha adrenergic input, somatostatin, and peptide YY (at the distal end of SI)
Phase of pancreatic secretion - interdigestive - During the “fed” state, there is a __ fold (inc/dec) in pancreatic secretions
5-20 fold INCREASE
Phase of pancreatic secretion - interdigestive - The spike in secretion during the “fed” state is primarily regulated by
CCK
However multiple signals inc pancreatic secretions
Phase of pancreatic secretion - interdigestive - during “fed” state, pancreatic secretions inc. What brings them back to basal levels
Peptide YY and somatostatin play important roles in returning the pancreatic secretion levels back to basal
Phases of pancreatic secretion
Cephalic
Gastric
Intestinal
Phases of pancreatic secretion - Cephalic
Stimulant?
Regulation pathway?
% max enzyme secretion
Stimulant = sight, smell, taste, mastication
Regulation pathway = Vagal pathways
% Max enzyme secretion = 25%
Phases of pancreatic secretion - Gastric
Stimulant?
Regulation pathway?
% max enzyme secretion
Stimulant = Distention, gastrin, peptides/peptones
Regulation pathway = Vagal/Gastrin
% Max enzyme secretion = 10-20%
Phases of pancreatic secretion - Intestinal
Stimulant?
Regulation pathway?
% max enzyme secretion
Stimulant = Amino acids, fatty acids, H+
Regulation pathway = CCK, Secretin, Enteropancreatic reflexes
% Max enzyme secretion = 50-80%
Phases of pancreatic secretion - greatest amount in what phase
Intestinal
Stimulated by nutrients (mainly fatty acids) which lead to release of CCK
Key regulators of pancreatic secretions - what are the primary nutrient regulators
Lipids or fatty acids are the primary nutrient regulators of pancreatic secretion
Lipids in the duodenum induce the release of CCK from I cells
Key regulators of pancreatic secretions - Others (besides nutrients)
Vagal stimulation
Gastric acid
Key regulators of pancreatic secretions - Others - Vagal stimulation - how?
Promotes the release of both pancreatic enzymes from acinar cells and HCO3 from duct cells
Key regulators of pancreatic secretions - Others - Gastric acid - How?
Promotes the release of secretin from duodenal S cells
Secretin will stimulate the duct cell to secrete HCO3
Pancreatitis - define
Inflammation of the pancreas
Pancreatitis - Common causes
Alcohol, gallstones, hypertriglyceridemia, blunt abdominal trauma, antimetabolites, estrogen, tetracylcine, HIV meds, or postoperatively
Pancreatitis - Description
Generally 3 phases
1 Initial - intrapancreatic digestive enzyme activation and acinar cell damage
2 Intrapancreatic inflammation
3 Proteolytic enzyme and cytokines effect distant organs
Pancreatitis - Consequences
Can range from mild, acute pancreatic complications to chronic and irreversible pancreatic damage
