GIM 2 Flashcards
What are the 3 regions of the pharynx?
Nasopharynx
Oropharynx
Laryngopharynx
What are the different types of oral epithelium?
Masticatory epithelium - keratinized stratified squamous epithelium found on structures involved in chewing
Lining epithelium - non-keratinzied stratified squamous epithelium found on all other surfaces
What are the different types of tongue papillae?
Filiform - mechanical
Fungiform - thermoregulatory
Circumvallate - sensory
Foliate - sensory
What are the 3 main layers of oral cavity mucosa?
Epithelium - stratified squamous non-keratinizing
Lamina propria- papillary layer, reticular layer
Submucosa - salivary gland, nerves, veins, bone
What are the different types of taste receptor cells?
Type 1 - Epithelial sodium channel (ENaC) - salty Type 2 - T1R/T2R - unami, sweet, bitter Type 3 - TRP receptor - sour Type 4 - replace taste receptor cells G-protein receptors in GI tract
What is the structure of a taste bud?
Open to surface via a taste pore
Sensory fibres penetrate base
Shielded by a selective barrier
What are the 3 paired large salivary glands in the oral cavity?
Sublingual - under tongue
Submandibular - under jaw
Parotid - cheeks
What is the histological appearance of salivary glands?
Irregular lobes divided by connective tissue strands called septa
What are the 2 parts of a salivary gland?
Acini
Duct
What is a myoepithelial cell?
Spider like contractile cell that mediates salivary expulsion
What is the function of acinar cells?
Produce primary saliva secretion (isotonic with plasma)
Secrete some salivary proteins
What is the functions of salivary ductal cells?
Modify salivary secretion:
Actively reabsorb Na+ and Cl-
Secrete K+ and HCO3-
Create a secretion that is hypotonic to plasma
How does and increase in salivary flow rate affect electrolyte concentration?
Na+, HCO3- and Cl- increase where K+ remains the same
How does parasympathetic stimulation of acinar cells affect salivation?
Production of large volumes of serous saliva (enzyme rich)
Vasodilation
How does sympathetic stimulation affect salivation?
Production of small volumes of thick saliva (mucous rich)
What are the functions of saliva?
Digestion - enzymes Mucous - aids swallowing Protection - IgA Solvent for taste Moisturiser - aids speech Oral hygiene Bicarbonate neutralises food acids - reduces dental cavities
Why is stomach food storage important?
Allows a delivery rate to small intestine appropriate for optimal digestion
What are the 3 layers of the alimentary canal?
Inner pipe - mucosa
Buffer space - submucosa
Outer pipe - muscularis
What are the 2 types of outermost layers of the alimentary canal?
Adventitia- lining of intraperitoneal surfaces
Serosa- parts attached to other body regions
How is a tumour staged in layered organs such as the alimentary canal?
By which layers are involved regardless of size
What epithelium is found in the oesophagus?
Non-keratinizing stratified squamous epithelium
What are the two main types of oesophageal cancer?
Squamous-cell carcinoma - tobacco, alcohol
Adenocarcinoma - long term acid reflux
What are the two types of stomach mucosa?
Non-oxyntic - mucus producing
Oxyntic - acid and pepsinogen producing
Describe the gastric mucosa
Hugh glandular mucosa forming gastric glands. Surface covered in thick mucus
What are the 4 different gastric epithelial cells?
Mucous - secrete mucus and bicarbonate
Parietal/oxyntic - secrete intrinsic factor and H+ ions
Enteroendocrine - secrete gut hormones
Chief/zymogenic - secrete pepsinogen
What is the purpose of mucus in the stomach?
Lubricant to prevent mechanical damage
Traps bicarbonate
Traps epidermal growth factor (EGF) which supports healing of gastric mucosal damage
How is the gastric wall protected from the acidic environment in the stomach?
As more acid is secreted by parietal cells, more bicarbonate is created and delivered to mucosal cells as a protective barrier
Why is surface folding in the GI tract so important?
Increased surface area for absorption of nutrients
In the stomach, what cells produce HCl?
Parietal
What is the role of secreted HCl in digestion in the stomach?
Activates pepsin and provides optimal pH
Aids breakdown of connective tissue and muscle fibres
Non-specific defence mechanism
What is the role of intrinsic factor (IF) in digestion?
Binds vitamin B12 and allows its absorption in the ileum
Secreted by parietal cells
What happens in the cephalic phase of gastric secretion?
What nerve is active?
Before food arrives, gastric secretion stimulated by expectation of food
Activity of vagus nerve
What happens in the gastric phase of gastric secretion?
When food reaches the stomach.
Mechanical stimulation of food in antrum induces local vago-vagal reflexes
Peptide fragments stimulate gastrin release from G-cells
What happens in the intestinal phase of gastric secretion?
Circulating amino-acids and gastrin act on parietal cells
What is gastrin?
Peptide hormone that stimulates the release of HCl by parietal cells
How is gastrin production regulated?
Somatostatin release inhibits gastrin secretion when pH drops below 2
What is the function on bicarbonate in the duodenum?
Neutralise acid chyme for optimal digestion pH (neutral/slightly alkaline)
Micelle formation (fat absorption)
Protects duodenal mucosa
What is the role of pancreatic amylase?
Digestion of carbohydrates (splits a-1,4 glycosidic links)
How are monosaccharides transferred from gut lumen to vascular system?
Sodium co-transporters
What are the 2 major classes of pancreatic proteolytic enzymes?
Endopeptidases - cleave interior peptide bonds
Exopeptidases - cleave external peptide bonds
How are proteins broken down after the stomach?
Pancreatic proteolytic enzyme break down proteins into peptides
Peptides broken down into amino acids by peptidase on the brush border of epithelial cells.
How is fat digested?
Bile acids emulsify lipid droplets to increase surface area and create micelles to enable absorption
What happens to lipids after absorption?
Resynthesized into triglycerides and combine with protein, phospholipids and cholesterol to form a chylomicron
How is pancreatic secretion stimulated?
Vagus nerve - cephalic and gastric phases
Secretin - stimulates HCO3- when acid in duodenum
Cholecystokinin (CCK) - stimulates enzyme rich secretion when fat and protein in duodenum
How are pancreatic secretions reduced?
Sympathetic activation and somatostatin
What is commensal flora?
Micro-organisms that are resident without damage to the host. Can be beneficial
What are transient flora?
Micro-organisms that reside for a short time without damage to the host
What are opportunist flora?
Only capable of invading or damaging host when immunity is compromised
What is campylobacter?
Acquired from raw food with a 2-5 day incubation. Symptoms of diarrhoea, abdominal cramp and vomiting.
What is Haemolytic Uraemic Syndrome (HUS)? What causes it?
Damage to the small blood vessels of the kidneys that lead to platelet destruction and anaemia. Caused by E. coli 0157 and increased risk with antibiotics
How would you diagnose Helicobacter pylori infection?
Urease breath test:
Carbon-13 urea swallowed, H-pylori breaks down urea, carbon dioxide with carbon-13 is exhaled
What does Helicobacter pylori infection cause?
Chronic gastritis
Duodenal ulcer disease
Inflammation
What treatment method is used to eradicate H-pylori infection?
Triple therapy. Combination of 2 antibiotics from metronidazole, amoxicillin and clarithromycin and a PPI and/or H2 antagonist.
1 week then PPI alone
What is gastro-oesophageal reflux disease (GORD) and what does it cause?
Reflux of gastric contents into oesophagus that leads to oesophagitis (heartburn)
What is the main cause of peptic ulceration?
H-pylori infection
How is gastric acid secretion increased?
Histamine (H2 receptors)
Gastrin
Acetylcholine ((M receptors)
How is gastric acid secretion decreased?
Prostaglandins
Bicarbonate and mucus release
What are the benefits of antacids with dyspepsia treatment?
What are some examples?
Rapid relief but not a cure. Raise pH
Sodium bicarbonate, magnesium hydroxide
What are alginates and how do they work?
Alginic acid when combined with saliva forms a foam which floats on gastric contents and protects the oesophagus during reflux
How do histamine receptor antagonists provide dyspepsia relief?
Prevent activation of histamine receptors which increase cAMP leading to H+ release from parietal cells. Provide short term symptomatic relief
How do PPIs help treat dyspepsia?
Irreversible inhibition of proton pump inhibitor, inhibiting H+ secretion. Higher risk of campylobacter infection.
What is an example of a PPI?
Omeprazole
How do NSAIDs cause gastric ulceration?
NSAIDs inhibit cyclo-oxygenase. COX-1 is linked to gastric protection.
How do you minimise GI damage from NSAIDs?
Prescribe with PPI and misoprostol (PGE1 analogue that acts on prostanoid receptors to inhibit gastric H+ secretion)
