SECRETIONS OF THE PANCREAS Flashcards
Give 3 functions of the pancreas
- Important in digestion of nutrients, fat, protein
- Provides the appropriate environment for enzymatic digestion in the small bowel
- Regulates the fed and fasted states
What is the pancreas divided into and what do these drain into?
Lobules which drain into a ductular network
Name three types of ducts found in the pancreas
- Intralobular duct
- Interlobular duct
- Main duct
What is the function of the Oddi of the pancreas?
Regulates and prevents reflux
What is the acinus?
A cluster of acing cells that synthesise and secrete proteins into the lumen of the epithelial structure
What do pancreatic acinar cells secrete?
- Zymogens
- Digestive enzymes
- isotonic plasma like fluid that accompanies secretory proteins
What are zymogens?
Inactive enzyme precursors
What is the function of pancreatic duct cells?
Specialised for the transport of electrolytes
What is the function of centroacinar cells?
Function is questioned but they are located at the junction of the pancreatic acinar cells and duct cells
What is the function and importance of goblet cells?
Produce mucus important for
- Lubrication
- Hydration
- Mechanical production of surface epithelial cells
- Prevents pancreatic infections
What do acinar cells do in the unstimulated state?
Secrete low levels of digestive protein via a constitutive secretory pathway
How are acinar cells stimulated?
Stimulation is mediated through CCK receptors and muscarinic acetylcholine receptors on the basolateral cell membrane.
What signal pathway do acinar cells use?
The phospholipase C/ Ca2+ signal transduction pathway. PLC/PKC / Ca2+
What activates PKC which leads to the release of calcium? (2)
- ACh
- CCK
What is the main function of the pancreatic duct cell?
It secretes HCO3- rich fluid which alikalinises and hydrates protein - rich primary secretions of the acinar cell
What is the HCO3- rich fluid released from the pancreatic duct cell important for? (3)
- Enzymatic optimal pH
- Micelle formation
- Neutralising acid
What are the two major triggers of the pancreatic duct cell?
Secretin and ACh
Explain how Cl- recycling works
- The chloride channel that is involved in the exchange of Cl- and HCO3- is known as CFTR
- It is a cAMP activated Cl- channel
- It is found on the apical membrane of pancreatic duct cells
- Cl- diffuses out of the duct cells cytoplasm into the lumen of the duct by cystic fibrosis transmembrane regulator (CFTR)
- Cl- then cycles back into the cell via the Cl-/HCO3- exchanger
Where is secretin produced and what does it stimulate?
- Produced in S cells
- Stimulates HCO3- and fluid secretion by the ducts
What happens when the secretin receptor is activated?
- Adenylyl cyclase is stimulated
- This raises cAMP
- Raised cAMP triggers PKA
What type of mutation causes Cystic fibrosis and what is the consequence of this mutation?
- A mutation on the CF gene which alters the function of the CFTR exchanger
- The CFTR exchanger is prematurely degraded which leads to decreased secretion of HCO3 and water by the ducts
- There is protein rich primary secretion which causes ductal obstruction and damage to pancreatic tissue
- A reduced amount of pancreatic enzymes leads to maldigestion of nutrients
What is pancreatic juice and how much is produced per day?
- Pancreatic juice which is protein rich which is produced from the products of acinar, duct and goblet cells
- 1.5 L is produced per day
What inhibits pancreatic secretions and how?
Somatostatin inhibits pancreatic secretions by inhibiting the release of CCK and secretin
What are the three phases of pancreatic secretion and which one is responsible for the highest level of pancreatic secretion?
- Cephalic phase
- Gastric phase
- Intestinal phase
