Secretion In GIT Flashcards
What are the 4 key components of all digestive secretions?
1) Water
2) Ions
3) Mucous
4) Enzymes
What are 4 functions of saliva?
1) Lubrication (mucin facilitates chewing and swallowing)
2) Antibacterial effect (lysosome and antibodies in saliva)
3) Enzymic digestion (amylose breaks down starch)
4) pH regulation (bicarbonate neutralises acid produced by bacteria)
Complete the sentence:
Saliva secretion is entirely under ….
Neural control
What are the 4 types of cell found in the glandular part of the stomach?
- Mucin producing cells
- Parietal cells
- Chief cells
- Endocrine cells
What are the functions of mucin producing cells, parietal cells and chief cells?
- Mucin producing cells produce mucous
- Parietal cells produce hydrochloric acid
- Chief cells produce pensinogen
What are the 3 types of endocrine cells found in the glandular region of the stomach?
1) G cells (produce Gastrin)
2) ECL cells (produce histamine)
3) D cells (produce somatostatin)
What is the purpose of intrinsic factors within the stomach?
Intrinsic factors help to ensure absorption of B12 in the stomach
How does somatostatin impact G cells
Somatostatin has a negative impact on G cells (the more somatostatin produced, the fewer G cells there are)
What are the 3 phases of gastric secretion?
Cephalic Phase
Gastric Phase
Intestinal Phase
What is the difference between each of the 3 phases?
Cephalic phase is elicited by sight/ smell/ taste of food. It is mediated by the vagus nerve.
Gastric phase is elicited by presence of food in the stomach, mediated by neural reflexes abdominal hormones.
Intestinal phase mediated via neural reflexes and hormones
During the intestinal phase of gastric secretions, there is initially a simulator effect then followed by an inhibitory effect, why is this?
To ensure that secretions are not continuous
What are the exocrine and endocrine functions of the pancreas?
Exocrine: produces pancreatic juices
Endocrine: Produce insulin, glucagon and somatostatin
Roteases digest proteins, what are the 3 proteases produced by the pancreas?
Trypsinogen -> trypsin
Chymotrypsinogen -> chymotrypsin
Procarboxypeptidase -> carboxypeptidase
What is the function of alpha amylase?
To digest starch
Lipase digest fats, what are the 3 lipases produced by the pancreas?
1) Triaglycerol hydrolase
2) cholesterol ester hydrolase
3) Phospholipidase A2
What are the key points about the Cephalic phase of pancreatic secretions?
- Cephalic phase increases in association with feeding
- Mediated by vagal nerves that run into the glands
- Affected by Gastrin secretion in the stomach
What are the key points about the gastric phase of pancreatic secretions?
- Increases in association with feeding
- Mediated by vagal nerves to the glands and Gastrin secretion in the stomach
When does the intestinal phase of pancreatic secretion begin?
When chyme enters the duodenum
How is the intestinal phase of pancreatic secretion mediated?
Mediated by secretin and CCK release
What is the function of secretin?
- Inhibits Gastrin release from G cells
- Inhibits response of parietal cells to secretagogues
- Stimulates pancreas to produce HCO3- rich fluid
- Increase production of bile by the liver
What is the function of CCK?
Inhibits secretions from parietal cells
Stimulates pancreas to increase enzyme secretion
What is the role of the liver in digestion?
- Hepatocytes produce bile
- Regulates the release of nutrients into the blood
What is the name of the ducts that secrete bile?
Bile canaliculi
How does the sphincter of oddi control the release of bile?
When the sphincter is relaxed, bile is released into the small intestine
When it is contracted, no bile is released.
What does bile contain?
- 95% water
- Bile acids
- Cholesterol
- Phospholipids
- Bile pigments
How are primary bile acids made?
Synthesised from cholesterol in the hepatocyte
How are secondary bile acids deformed?
When primary bile acids undergo dihydroxylation by bacteria in the small intestine
How are bile salts formed?
Primary and secondary bile acids conjugate with an amino acid (taurine/ glycine)
What is the function of bile salts?
Act as detergents to emulsify lipids
Form micelles
How do bile acids recirculate back to the liver?
By enterohepatic circulation
What happens when fat is detected on CCK producing cells?
- More CCK produced
- Sphincter of Oddi opens
- More bile released into small intestine
