Pacreatic Exocrine Secretion Flashcards
What does the pancreas do?
Bicarbonate secretion
Bicarbonate secretion
Total 1 litre/24 hours
Bicarbonate production is dependant on Epithelial cells in Pancreatic duct producing HCO3- & H2O
Bicarbonate secretion protects duodenal mucosa by
neutralising stomach acid
Buffers duodenal contents to optimise pH for enzyme digestion
Resting phase maintains low flow- predominantly Na+ & Cl- ions
High flow rates Na+ & HCO3- ions
The pancreas is continually secreting bicarb and water, but it’s in stimulation to food entering the stomach and other
stimuli to then get high rates of flow to aid digestion
Enzymes- proteases
Protein digestion is initiated by pepsin in the stomach
Majority occurs in small intestine
Pancreatic proteases: trypsin and chymotrypsin
Stored as proenzymes (trypsinogen and chymotrypsinogen) to ensure no damage to the cells own proteins
Trypsinogen activated by enterokinase which is secreted by small epithelial cells
Trypsin activates chymotrypsinogen and additional trypsinogen
Once the proteases have been exosytosed from the secreted vesicles the trypsin inhibitor is also diluted and then becomes ineffective as it is overwhelmed by the amount of trypsin and chymotrypsin
Enzymes- lipases
Triglycerides cannot be absorbed across intestinal mucosa
Lipases hydrolyse triglycerides to monoglyceridees and free fatty acids
Bile salts (come out in response to CCK once you’ve eaten a meal) aid triglyceride digestion and absorption of monoglycerides and free fatty acids
Fat digestion is dependent on pancreatic and hepatic secretion
Orlistat- pancreatic lipase inhibitor (antibody drug)
Enzymes- amylase & others
Hydrolyses starch to maltose (glucose- glucose disaccharide) and maltotriose (trisaccharide) and limit dextrins
Pancreas is major source of amylase
Salivary amylase has a small role
Ribonuclease, deoxyribonuclease, gelatinase and elastase are helpful in metabolising
Enzyme secretion
Cephalic stage: anticipatory stage where we can sense theres a meal coming due to vagus innervation and pelvic
This results in start of salivation and gastric in stomach
Low level stimulus in anticipation of a meal
Intestinal stage where secretin, cholecystokinin and gastrin are secreted
Secretin will cause a flush out of bicarbonate and water for the pancreas and all of the enzymes will get flushed down the pancreatic duct into the second part of the duodenum
Control of secretion
Slide 15
Control of secretion
Pancreatic secretions contain enzymes to digest protein, starch and triglyceride
Gastrin and CCK stimulate enzyme secretion and neutralise gastric acid entering small intestine
As proteins and fats are digested and absorbed, pH rises and stimuli for CCK an secretin disappear and pancreatic secretion reduces
Endocrine function
Insulin and glucagon are vital for carbohydrate and lipid metabolism
Pancreatic exocrine insufficiency
Symptoms
Maldigestion, diarrhoea, steatorrhoea, weight loss
Consequences
Malnutrition
Osteoporosis
Increased cardiovascular morbiditiy
Symptom burden
