Week 2 - Peptic Ulceration Flashcards
What are the 4 types of salivary glands?
Parotid - in cheek - serous, watery secretion
Submandibular - under chin - mainly serous secretion
Sublingual - under tongue - mainly mucous secretion
Simple - random places - mainly mucous
What is the role of acinar cells?
Responsible for primary secretion, isotonic with plasma
Some salivary proteins secreted
What is the role of duct cells?
Modify secretion by acinar cells
Actively reabsorb Na+ and Cl- ions
Secrete K+ and HCO3- ions
Impermeable to water
Excess absorption = saliva is hypotonic to plasma
Lable the 4 cell types?
What are the functions of saliva?
- Breakdon food components
- Activate taste buds
- Produce mucus for swallowing
- Moisturiser to aid speech
- Promotes oral hygeine
- Contains bicarbonate –> neutralises acids in food reducing cavities
What happens to ion concentrations when high salivary flow rate?
What happens when acinar cells are parasympathetically vs sympathetically stimulated?
Para = + serous saliva is produced, rich in enzymes
Symp = small amount of thick saliva rich mucous produced
What role does bradykinin have in saliva production?
+ bradykinin = vasodilatation = increase in saliva secretion
What are the 2 phases of swallowing?
Oropharyngeal –> food bolus directed into oesophagus
Oesophageal –> oesophagus is protected from damage caused by passing food bolus via mucous secretion
What are the 2 regions of gastric mucosa?
Where are mucosal gland cells found?
Oxyntic mucosa = in fundus and body of stomach
Pyloric gland area = in antrum
In gastric pits
What is the role of parietal, cheif and surface epithelial cells in stomach?
Parietal = secrete HCl and intrinsic factor
Cheif = secrete pepsinogen
Surface epithelial = secrete mucous
How do parietal cells produce HCl?
P takes H+ in exchange for K+
A moves carbonate into blood and Cl- into cell
C transports Cl- and K+ into gastric lumen
What is the relationship between stomach HCl and pepsinogen?
HCl = provides acidic environment for pepsin to digest food
What is the cephalic phase of gastric secretion?
- Gastric secretion stimulated prior to food arriving
- Stimulated by thought of expectation
- Contributes 30-50% gastric secretions
- Is dependent upon vagus nerve activity
What is the gastric phase of gastric secretion?
- When food reaches stomach
- Contributes 50-60% gastric secretions
- Occurs due to local vagal reflexes in response to mechanical stimulation
- Gastrin release from G-cells stimulated by peptide fragments of partially digested proteins
What is the intestinal phase of gastric secretion?
- Contributes 5% of gastric secretions
- Due to circulating AAs or gastrin
What effect does pH and enterogastrone have on gastrin release?
pH < 2 = inhibition of gastrin release from G cells via somatostatin release
Enterogastrone = released when duodenum distended or chyme = inhibits gastrin release
How are gastric mucosa protected from autodigestion?
Luminal membranes = H+ impermeable = connected via tight junctions = no H+ between cells
Negative feedback = pH less than 2 inhibits G-cells via somatostatin from D-cells
Mucus = release from surface epithelial cells
Rapid repair of damaged mucosa
What is the role of duct cells, centrocinar and acinar cells in the pancreas?
HCO3- exchange with Cl-
Bicarbonate secretion for neutralising acid chyme
Enzyme rich alkaline secretion
What controls pancreatic secretions?
What is the role of acetylcholine in the pancreas?
Vagus nerve
Potentiates actions of secretin and cholecystokinin
What are the functions of secretin and cholecystokinin?
Secretin = released in repsonse to acid in duodenum –> stimulates HCO3- production
Cholecystokinin = stimulates enzyme rich secretion released in response to fat and protein in duodenum
Wjhat is the role of somatostatin in the pancreas?
Inhibits pancreatic secretions
How are carbohydrates digested in the SI?
- Digested as complex carb
- Digestion ceases in acidic stomach environment
- digestion from pancreatic alpha-amylase
- Subsequent digestion by enzymes of SI brush border
- Sodium dependent process
How are proteins digested in the SI?
- Digested in stomach by pepsin
- Halted by alkaline pancreatic secretions
- Endo and exopeptidases are pancreatic enzymes for digestion
- Enzymes secreted in inactive form into duodenum
- Further digestion by peptidases on brush border, fomring AAs
- Absorbed via passive diffusion or facilitated transport
- Intracellular peptidases breakdown peptides
How are lipids digested in the SI?
- Digested by pancreatic lipase (water soluble)
- Fats emulsified by bile acids from liver, released by gall bladder
- Monoglycerides and FFAs formed from pancreatic lipase action (absorbed by forming micelle)
- Triglycerides reformed intracellularly, combined with phospholipids, cholesterol and protein
- Forms chylomicron
- Chylomicron is transported via lymphatic system
What are the main investigations for GI infection?
Grow bacteria in culture
Look for specific toxins
Look for parasites with microscope
Attempt to detect specific antigens / antibodies
What are problems with C. diff infection?
- Vegetative cells produce toxin
- Can colonise and not cause disease
- Antibiotics kill other bacteria, allowing C. diff to thrive
- Disease = diraahoea - toxic megacolon - perforation
- Metronizadole for mild disease, vancomycin for severe
What are problems with H. pylori infection?
- Chronic gastritis
- Bacterial
- Duodenal ulcer disease = 80%
- Inflammatory response
- Association with gastric adenocarcinoma
- Urea breath test, gastric biopsy, serology
- 2 antibiotics + PPI for treatment
What are 4 anti-emetic drugs?
H1-receptor antagonists
Anti-muscarinic agents
Dopamine antagonists
5-hydroxytryptamine antagonists
What are 3 common causes of diarrhea?
Rotavirus - damages small bowel villi
Invasive bacteria - damage epithelium
Adhesive enterotoxigenic bacteria - adhere to brush border, + cAMP, Cl- and Na+ secretion followed by water
When are antibiotics, orlistat, misoprostol and PPIs used in diarrhoea?
Antibiotics = superinfection
Orlistat = Pancreatic lipase inhibitor used for steatorrhea
Misoprostol = used for inflammatory type response
PPIs = used in infectionq
How do opioids help in diarrhoea?
Reduce tone and peristaltic movements of GI muscles
Reduce ACh release
+ transit time
+ water reabsorption
Symptomatic relief
Can cause constipation
How can you treat constipation?
Osmotic laxatives:
- Lactulose
- Macrologs
- Magnesium
Bulking agents stimulating GI activity:
- Stimulant laxatives
- Prucalopride
Treatment for IBS?
Lactulose or loperamide
Antispasmodics
Amitriptyline
How do you treat IBD?
Anti-inflammatories and immunosupressants
- 5-aminosalicylates
- Corticosteroids
- Immuniosupressants
