GI Tract II Flashcards
Why do we chew?
- Fruit and veg have indigestible walls
- To increase SA:V
- Finer particles prevent blockages
Distribution of skeletal and smooth muscle in the oesophagus
Upper 1/3 - skeletal
Lower 2/3 - smooth
Location of the oesophagus
Runs posterior to trachea, heart and lungs, anterior to vertebrae and pierces the diaphragm before entering stomach
What is primary peristalsis?
Continuation of peristaltic wave that commences in oropharynx and spreads to oesophagus
What is secondary peristalsis?
Sweeps down any remaining food. Trigger is distension of oesophagus
Which cranial nerves innervate the skeletal muscle of the upper 1/3 of the oesophagus?
CN IX and CN X
Which cranial nerves innervate the smooth muscle of the lower 2/3 of the oesophagus?
CN X
What is a hiatus hernia?
Loss of fat by the plug between oesophagus and stomach. Acid refluxes and enters bottom of oesophagus –> heartburn
Give an example of a disease associated with the oesophagus
Barrett’s oesophagus
What is Barratt’s oesophagus?
Metaplasia (abnormal change) of cells lining lower oesophagus
What change occurs in Barratt’s oesophagus?
The normal stratified squamous epithelium is replaced by simple columnar epithelium with goblet cells (found in stomach)
Symptoms of Barrett’s oesophagus
None but associated with acid reflux
- heart burn
- dysphagia
- Haematemesis
- Erosion of teeth
How can you treat Barratt’s oesophagus?
Get rid of acid
-Proton pump inhibitor
Endoscopic surveillance
oesophagus resection
The main way to manage Barratt’s oesophagus is to get rid of the acid but what would be an adverse effect of this?
More susceptible to food poisoning
What kind of circles does food in the stomach form?
Concentric circles - old food by the wall, newest food in the centre
What do G cells in the stomach secrete?
Gastrin
What is gastric juice secreted by?
Gastric glands that cover almost the entire lumen of the stomach
Which GI tract structure provides the most potent signals in controlling stomach emptying?
Duodenum
Factors that increase rate of stomach empyting
- Increased food volume in the stomach
- Gastrin - hormone produced by G cells in the astral mucosa. Mainly increase production of gastric juice. Also stimulates motor activity of pyloric pump
Factors that decrease rate of stomach emptying
Stretch of duodenal wall
- directly inhibits pyloric pump via enteric nervous system in the gut wall
- vagus nerve to brainstem –> inhibit excitatory signals to stomach
Give an example of a pathology of the stomach
Peptic ulcer
What is a peptic ulcer?
Damage to the wall of the stomach by stomach aid
What lines the inside of the stomach so that it doesn’t get damaged?
Mucus
Causes of peptic ulcers
Helicobacter pylori —> chronic inflammation in the astral mucosa
- acid secretion –> erosion of gastric wall
Non-steroid anti-inflammatory drugs e.g. ibuprofen (long term/high doses)
How could you treat peptic ulcers?
- Proton pump inhibitor
- ‘triple therapy’ if caused by Helicobacter pylori
Lamoxicillin, Clarithromycin and PPI
Where does gastric cancer develop from?
Lining of the stomach
What are the folds that increase the surface area for absorption in the GI tract and where are they most well-developed?
Folds of Kerckring
Well-developed in the duodenum and jejunum
What are fats broken down into?
Monoglycerides and free fatty acids
Breaking down fat mechanism
- Micelles carried to the brush border and penetrate the recesses in between the agitating microvilli
- The monoglycerides and free fatty acids diffuse out of the micelle into the interior of the epithelial cell. Micelles remains in chyme and emulsifies more fats acting as a ‘ferry’
- Monoglycerides and free fatty acids are taken up by smooth ER, converted into triglycerides and released to form chylomicrons through the basolateral membrane, up through the thoracic lymph duct and emptied to the blood
What are Peyer’s patchers?
Areas of lymphoid tissue for local immune protection
Why does the colon have a high concentration of goblet cells?
Mucus secretion
What are haustra?
The pockets which give the colon a segmented appearance
What are the tenia coli?
3 bands of longitudinal muscle seen on the ascending, transverse, descending and sigmoid colon
What does aldosterone enhance at the large intestine?
Na+ absorption
What happens at the colon when dehydrated?
Lots of aldosterone secreted by the cortices of the adrenal gland
Composition of faeces
3/4 water and 1/4 solid matter
What gives faeces their brown colour?
Stercobilin and urobilin
