Upper GI Tract Flashcards
- Give a brief definition of digestion
- Give a brief definition of absorption
Process of breaking down macromolecules to allow absorption
Process of moving nutrients and water across a membrane
- Describe the distribution in the number of teeth in the oral cavity
8 incisors
4 canines 8 premolars 12 molars
- What is the largest jaw muscle and the muscle in charge for biting?
- What are the 2 enzymes released by the salivary glands?
Masseter
Lingual lipase (fat digestion) Salivary amylase (carbohydrate digestion)
- What are the intrinsic muscles of the tongue responsible for?
- What are the extrinsic muscles of the tongue responsible for?
Fine motor control and moving food
Gross movement of tongue Assists mechanical digestion
- Which vertebrae is the oesophagus between?
- What are the three subdivisions of the oesophagus?
C5 and T10
Cervical oesophagus - cricopharyngeal muscle to suprasternal notch Thoracic oesophagus - suprasternal notch to diaphragm Abdominal oesophagus - diaphragm to cardia of stomach
- What is the function of the oesophagus?
- How does the structure of the oesophageal epithelium relate to its function?
Conduit for food, drink and swallowed secretions from pharynx to stomach
Non-keratinising Wear & Tear lining - to withstand extreme temperatures and aid texture Lubrication - mucus secreting glands (goblet cells)
- What is the Z line in the oesophagus?
Line where the pink mucosa of the oesophageal sqaumous epithelium meets the red mucosa of the gastric columnar epithelium
- What is the significance of this Z line in Barrett’s oesophagus?
- What is Barrett’s oesophagus?
Here, the epithelium of the lower oesophagus undergoes metaplasia
So the gastric mucosa extends into the oesophagus, meaning it would be important to determine the Z line in these cases
when the separation between pink (oesophagus) and red (stomach) mucosa is higher than normal
- Is the upper or lower oesophageal sphincter a true sphincter?
- Is skeletal muscle found in the upper or lower oesophagus?
- Is smooth muscle found in the upper or lower oesophagus?
upper
both
lower
- Why does this epithelial transition at the gastro-oesophageal junction occur and how does this develop to cancers?
Acid reflux means that the lower oesophagus is more acidic than normal
To cope with this, the squamous cells above the gastro-oesophageal junction become columnar epithelium- columnar are more resistant to acid This change to columnar epithelium makes the cells unstable, leading to dysplasia and then becomes cancers
- Why is a hiatus hernia a risk factor for developing cancer of the oesophagus?
Because the opening of the diaphragm causes it to be larger and so there is a portion of the stomach that slips into the chest which prolongs exposure to the lower oesophagus, associating with acid reflux
- How does the anatomical orientation of the stomach to the oesophagus reduce the risk of acid reflux?
Stomach lies at an angle to the oesophagus
Other ligaments also suspend the gastro-oesophageal junction at an acute angle to prevent acid reflux
the diaphragm also prevents reflux
- what are gastric folds
- Why are the gastric folds present?
coiled tissue in mucosal and submucosal layers of stomach
To increase the surface area of the epithelium of the gastro intestinal tract so that more amount of digestion and more absorption can occur
What happens in the oral phase of swallowing?
Chewing and saliva prepare bolus
Both oesophageal sphincters constricted
What happens in the Pharyngeal Phase?
Pharyngeal musculature guides food bolus towards oesophagus
Both oesophageal sphincters open
What happens in the Upper Oesophageal Phase?
Upper sphincter closes
Superior circular muscle rings contract and inferior rings dilate
Sequential contractions of longitudinal muscle
What happens during the lower Oesophageal Phase?
Lower sphincter closes as food passes through
- What are the functions of the stomach?
Breaks food into smaller particles (acid & pepsin)
Holds food, releasing it in controlled steady rate into duodenum Kills parasite and certain bacteria
- What do the cardia and pyloric regions of the stomach secrete?
- What do the body and fundus of the stomach secrete?
- What does the antrum of the stomach secrete?
mucus only
Mucus, HCl, Pepsinogen
Gastrin
- How much acid is produced per day by the stomach and what is the H+ concn. of this acid?
- What allows the pH of the epitheliual surface to be between 6 and 7 when the lumen is between 1 and 2?
2L
150mM H+
Mucus coating with HCO3- trapped in the mucus gel
- Which layer of muscle carries out segmentational contraction?
- Which layer of muscle carries out peristalsis contraction?
Circular
Longitudinal
- Is segmentation or peristalsis the stronger contraction?
- Which method of contraction occurs most often?
Peristalsis
Segmentation - 80% of contractions
- Where does peristalsis propel chyme to?
- Where does segmentation move chyme to?
Towards the colon
Fluid chyme towards pyloric sphincter Solid chyme pushed back to the body
- Describe the nervous stimulation of peristalsis?
- Describe the nervous stimulation of segmentation?
Activated by the ANS
Stretching activated enteric nervous system
- What do the chief cells of the stomach secrete?
- How are these chief cells adapted to secretion?
Pepsinogen
Abundant RER Golgi packaging and modifying for export Masses of apical secretion granules
- What do the paritetal cells of the stomach secrete?
- How is the parietal cell adapted for this function?
Hydrochloric acid (HCl)
It has many mitochondria It has cytoplasmic tubulovesicles which contain H+/K+ ATPase - responsible for the secretion of HCl into the lumen of the stomach contains Internal canaliculi (secretory surfaces)
- Explain how the parietal cells secrete HCl?
Na+/K+ pump, transports Na+ into interstitial fluid from the parietal cell and K+ transported from interstitial fluid into the parietal cell
K+ then moves into the canncaliculi that have fused with the tubulovesicles
CO2 taken up by parietal cells and reacts with H20 using carbonic anhydrase, forming H+ and HCO3- HCO3- transported out by AE1 antiporter and exchanged with Cl, which is transported into the parietal cell and then into cannaliculi H+/K+ ATPase transports H+ into the canaliculi and moves K+ from the canaliculi back into the parietal cell
- How is this HCl secretion triggered?
H2 receptors which are found on the surface of the parietal cells
When histamine gets released from different triggers, this is detected by the H2 receptors which starts the process of HCl secretion
- Describe the cephalic phase of gastric secretion
Thought, sight, smell and taste of food stimulates gastric secretion
Vagus nerve activates parietal cells through ACh to trigger the whole cascade
- Describe the gastric phase of gastric secretion
Food in stomach activates the stretch- and chemo-receptors
Signals sent to and from the brain via Vagus nerve to activate the secretion of acid
- Describe the intestinal phase of gastric secretion
Once the chyme with pH less than 2 reaches the duodenum
Signal is transmitted by the vagus nerve and this causes secretion of hormones that inhibit the secretion of gastric HCl and pepsin too These hormones are Gatric inhibtory peptide, Cholecystokinin and Secretin
- What is the enterogastric reflex?
Nervous reflex where stretching of the wall of the duodenum results in inhibition of gastric motility and reduced rate of emptying of the stomach
It is a feedback mechanism used to regulate the rate at which partially digested food leaves the stomach and enters the small intestine
- What is the mechanism of action of Omeprazole?
- What can Omeprazole be used as a treatment for?
Blocks the protein pumps (H+/K+ ATPase)
Indigestion, heartburn and acid reflux
- What is the mechanism of action of Ranitidine?
- Would chyme fatty acid content and protein content increase or decrease acid secretion in the stomach?
Blocks the H2 receptors to prevent the triggering of the whole cascade by Histamine
decrease
