Gastric motility and Pancreatic function Flashcards
Which direction do peristaltic waves travel in the stomach?
From the body along the pyloric antrum
Where does most of the grinding occur?
Pyloric antrum
What is the role of the pyloric sphincter?
It stops chyme (gastric content) going through too fast (keeps duodenum not too acidic, and also helps stop dumping syndrome (osmotic effect into duodenum if too many small particles ie food), also acts as a wall to keep food in stomach and keep food churning around in the stomach
Which nerve plexus sits between the circular and longitudinal layers of the stomach?
Myenteric plexus (muscle gut)
WHat genarates the peristaltic rhythm? What type of wave/rhythm do they produce? How are the waves conducted? Is this wave reachimng threshold? WHat determines strength of contraction?
- Genarated by pacemaker cells (in longitudinal muscle layer)
- Slow waves produces rhythmic depol/repol ~ 3/min
- conducted through gap junctions in longitudinal muscle layer
- wave does not reach threshold - more depol required to reach threshold
- strength determined by frequency of waves
What effects the contraction? 2 (increasing contraction, 1 inhibition of motility)
Increasing contraction:
-Gastrin
-presence of food (distension of stomach wall - long and short reflexes
Inhibiting motlity:
- presence of food in duodenum - fat/acid/amino acid/hypertonicity
Where are the glands in the stomach (histiologically)?
Mucosal layer
Where are glands found in th esubmucosa in the GI tract?
Oesophagus and duodenum
What ar ehte submucosa glands in the duodenum called?
Brunner’s glands
What is secreted by Brunners glands?>
Bicarbonate
What triggers HCO3 release?
Acid in duodenum….
-Long (vagal) and short (ENS) reflexes and HCO3 secretion
-Secretin release from S cells -> HCO3 from pancreas and liver. Inhibited by acid neutralisation
What type of control is the inhibition of secretion release?
Negative feedback
WHat are the 3 parts of the panceras and where are they?
Head, body, tail
Head in C
Where are hte endocrine portuion of the pancreas and what do they produc and secrete?
Insulin and glucagon.
In the islets of Langerhans
What controls the release of glucagon/insulin?
Somatostatin - inhibitory
Where are the exocrine portion of th epancreas? Which cells produce what?
In acinar bulb things aka LOBULES
Acinar cells = digestive enzymes
Duct cells = bicarbonate
How are lobules combine to form the main pancreatic duct?
By tubes called Intercalated ducts - intralobuleducts - interlobule ducts
What is the shincter of Oddi, waht is it ak?
The opening of the pancreatic duct into the duodenum
aka sphincter of ampulla or choledochal sphincter
WHat happens if pancreatic duct gets blocked?
Can go through accessory pancreatic duct!
What do duct cells release?
Bicarbonate (HCO3)
What do acinar cells secrete?
Digestive enzymes in the inactive form of Zymogens
Pancreatic duct cell shape? Intestinal cell shape?
Duct cells are more cuboidal, acinar cells are more columnar (beer can)
What is autodigestion?
Digestion of the body by its own digestive enzymes
How are our digestive enzymes stored?
As Zymogens (to become EN-ZYMes they need tripsinogen to be coverted to trypsin by ENterokinase and trypsin to take the -OGEN)
Why do we store zymogens rather than enzymes?
To prevent autodigestion
What is Enterokinase? WHere is it found? What doe sit do?
It is the enzyme (found in brush border of duodenal enterocytes) that converts trypsinogen to trypsin so that trypsin can go onto turn zymogens into digestive enzymes within the safety of the intestinal lumen.
What is the role of Trypsin?
To turn the zymogens into their respective digestive enzymes in the intestinal lumen
What secertes Trypsinogen?
The pancreas (alongside the Zymogens
Pancreatic Enzyme -Proteases: how does it work where?
Acid hydrolysis - v efficient in the stomach
Hydrolysis everywhere else (inc. large intestine)
Cleave and break down proteins (peptide bonds)
eg pepsin
Pancreatic Enzyme - Nucleases - do what?
They help break down (hydrolyse) DNA and RNA
Pancreatic Enzyme - Elastases
Break downt he connective tissue eg collagen, elastin
Pancreatic Enzyme - Phospholipases what do
Break down the cell wall (phsopholipids) into fatty acids
Lipases - what do (Pancreatic enzyme)
Turn Triglycerides into fatty acids and glycerol
Alpha amylase do what?
CHO (Startch) - glucose and maltose
What is Bicarbonate secretion stimulated by? What is it released in ersponse to?
Stimulated by acid in the duodenum -> stimulates secretin release -> Secretin stimulates Brunners glands (in duodenal wall) -> produces bicarbonate -> neutralises acid -> decreases stimulus and inhibits secretion release (negative feedback)
What is Zymogen secretion stimlus?
CCK - Cholecystokinin (secreted by small intestine in response to fatty acids and amino acids in the intestin)
Wjat is CCK released in response to?
Intestinal Fatty and Amino Acids
What is the neural control of the pancreatic function?
Vagal and local reflexes when there is organic nutrints in the duodenum (to secrete bicarbonate and pancreatic enzymes)
