Pancreas Flashcards
How is the pancreas positioned in the abdominal cavity
completely RETROPERITONEALapart from Tail
How is the tail of the of the pancreas arranged
The tail of the pancreas is attached to the spleen and is intraperitoneal
During trauma what can happen to the body of the pancreas
The body can be crushed against the vertebral bodies during trauma
What can inflammation/carcinoma of the pancreas cause
The head of the pancreas is closely related to the common bile duct meaning a carcinoma or inflammation of the head of the pancreas can block the bile ductresulting in post-hepatic/obstructive jaundice
How are the arteries arranged with the pancreas
the superior mesenteric vein & artery are entrapped between the head and uncinate process
What are the different parts of the pancreas derived from
The uncinate process comes from the ventral bud (the rest of the pancreas comes from the dorsal bud)
Why can a duodenal ulcer cause vomitting of blood
the superior gastroduodenal artery runs in close proximity to the duodenum, so a duodenal ulcer can eventually erode into the gasproduodenal artery resulting in haemorrhage and haematemesis (vomiting of blood)
How does the pancreas develop
The pancreas develops as two separate out growths - the ventral & dorsal pancreas and during development of the embryo the ventral bud rotates around and fuses with the dorsal pancreas - in effect becoming the head of the pancreas
Describe the blood supply of the pancreas
The pancreas receives its main blood supplyfrom the coeliac trunk which arises directlyfrom the aorta and divides at the coeliac axis to form the gastric arteries, the hepatic artery & the splenic artery
What does the ceoliac trunk divide into at the coeliac axis
gastric arteries, the hepatic artery & the splenic artery
What supplies the head of the pancreas and why is it arranged like it is
the splenic artery•The superior mesenteric artery which runs“through” the head for the simple reason that it is enveloped during the rotation when the dorsal and ventral pancreas fuse, provides some supply to the head of the pancreas
Describe the venous drainage of the pancreas
Venous drainage is achieved mainly by the splenic vein which then joins the superior mesenteric vein to form the portal vein
what does the exocrine pancreas secrete
- HCO3- (bicarbonate)
- Digestive enzymes
Where do the exocrine secretions come from in the pancreas
Secretions arise from the acinar tissue of the pancreas
How are things secreted from the pancreas
The secretions are secreted into ducts which converge into the pancreatic duct which in turn joins the common bile duct just before it enters the duodenum at the ampulla of Vater
Function of the sphincter of Oddi
The sphincter of Oddi is a separate bundle of circular muscle which regulates flow into the duodenum and may serve also to prevent mixing of bile & pancreatic juice within the pancreatic duct
What will reflex of bile down the pancreatic duct cause
Reflux of bile down the pancreatic duct will result in acute inflammation because of its detergent properties
where does the accessory pancreatic duct emerge
The accessory pancreatic duct usually emerges above the ampulla of Vater
What secretes HCO3-
why
Secreted by epithelial cells lining the ducts known as duct cells
In order to protect the duodenal mucosa from gastric acid
It also buffers the material entering the duodenum to a pH suitable for enzyme action
where is secretin produced
produced in the small intestine
What stimulates the secretion of HCO3-
The release of the gastrointestinal hormone SECRETIN in response to the presence of acid in the duodenum stimulates the secretion of HCO3 - from both the pancreas & liver & also potentiates the action of the hormone CCK (which stimulates enzyme secretion)
Other than stimulating CCK and HCO3- secretion what else does secretin do
Secretin also inhibits acid secretion and gastric motility in the stomach
What secretes HCO3- into the duct lumen. via what
The pancreatic duct cells secretes HCO3- into the duct lumen via an apical membrane Cl-/HCO3- exchanger
Cl-/HCO3- exchanger 1
What happens first
Formed by H+ which was pumped out of the duct cell in exchange for Na+ via a Na+/H+ exchanger
Cl-/HCO3- exchanger 2
what happens when H+ is pumped out of the duct cell in exchange for Na+
H+ then reacted with HCO3- in the blood resulting in the formation of carbonic acid (H2CO3) which then rapidly dissociates to H20 & CO2
Cl-/HCO3- exchanger 3
What happens when H2CO3 dissociates into H20 and CO2
CO2 then enters the duct cell via diffusion where, under the action of the enzyme carbonic anhydrase reacts with the H2O in the duct cell to produce carbonic acid which then dissociates to form H+ and HCO3-, the H+ can then be pumped out again via the Na+/H+ exchanger)
Where does the Exchange of H+ for Na+ occur
While the H+ prodcued is exchanged for extracellular Na+ on the basolateral side of the cell
What does the H+ exchanged do
The H+ enters the pancreatic capillaries to eventually meet up in the portal veinblood with the HCO3- produced by the stomach during the generation of luminal H+
What is the energy for secretion of HCO3- provided by
Na+/K+ - ATPase pumps on the basolateral membrane
Why does Cl- to accumulate within the cell
The Cl- normally does not accumulate within the cell because these ions are recycled into the lumen via the CFTR channel (Cystic Fibrosis Transmembrane Conductance Regulator)
Via a paracellular route Na+ & H2Omove into the ducts due to the electrochemical gradient established by chloride movement through the CFTR
What is paracellular route
(moving through spaces between the cells e.g. tight junction)
What is transcellular transport
Through membrane porters of channels (through the cell)
What is somatostatin and where is it found
produced by the D cells in the pancreatic islets/ islets of Langerhans is a powerfulinhibitor of pancreatic exocrine secretion
What cell types do the islets of langerhans contain
- Alpha cells - produce glucagon
- Beta cells - produce insulin & amylin
- Delta/D cells - produce somatostatin
- PP cells - produce pancreatic polypeptide
Function of alpha cells
produce glucagon
function of beta cells
produce insulin and amylin
Function of delta cells
produce somatostatin
Function of PP cells
produce pancreatic polypeptide
What does autoimmune destruction of the islets langerhans cause
diabetes mellitus i.e. normal diabetes
What is type 1 diabetes
pancreas failure to produce enough insulin
What is type 2 diabetes
cells fail to respond to insulin properly
When do most exocrine secretions happen
Intestinal phase
How does the cephalic phase effect pancreatic secretion
Initiated by the sensory experience of seeing & eating food and primarily involves parasympathetic vagus nerve stimulation of acinar cells to produce digestive enzymes
How does the gastric phase effect pancreatic secretion
Initiated by the presence of food within the stomach and also primarily involves parasympathetic vagus nerve stimulation of acinar cells to produce digestive enzymes
By the end of the cephalic & gastric phases, the pancreatic ducts are filled with inactive digestive zymogens ready for release into the intestinal lumenalong with bicarbonate via the sphincter of Oddi
When amino acids + fatty acids are present in the duodenum then CCK is released and the gallbladder contracts inducing enzyme secretion
