Oesophagus and Stomach Flashcards
What are the layers in the oesophagus? (4)
Mucosae
Submucosae
Muscularis
Serosal Adventitia
What is the mucosae layer made up of?
Epithelium
Lamina propria (loose connective tissue that connects the other two layers together)
Muscularis Mucosae
What does the submucosae contain?
Connective tissue containing nerve plexus and glands
Where does the oesophagus start and end?
Start at C5 and end at T10
How is oesophagus designed for it’s function?
It’s function is to deliver food
It has to be robust and handle extreme temperatures and textures by being stratified non keratinising squamous epithelia.
What is the upper oesophageal sphincter made from?
Skeletal muscle
What is the lower oesophageal sphincter made from?
Skeletal and smooth muscle
What is the function of the gastro-oesophageal junction?
acid reflux is prevented by the diaphragm and has an epithelial transition
What is the point of the gastric folds in the stomach?
The folds stretchh when the stomach fills it allows the stomach to get bigger. When the stomach is full the folds are gone and the stomach wall is smooth
Give an example of when the diaphragm fails to prevent acid reflux?
Pregnancy when foetus pushes stomach upwards
5 sections of the stomach and what do they make?
Cardia and Pyloric only make mucus
Body and Fundus makes mucus, HCl and pepsinogen
Antrum makes gastrin
What are the functions of stomach?
- break down food into smaller particles stored due to aid and pepsin
- hold food and release at a controlled steady state into duodenum
- kill parasites and certain bacteria
What do cardiac and pylori sections make?
Mucus secreting with lots of bicarbonate that neutralises the stomach acid as it is trapped in mucus gel. This means epithelial surface of pH 6-7 but the lumen pH 1-2. Bicarbonate prevents acid damaging the cells.
In the body and fundus, what is made?
- Make acid that denatures large proteins
- Pepsinogen producing which is precursor to pepsin which breaks down protein
- mucus producing but with no bicarbonate
What does peristalsis do in stomach?
Propels chyme towards colon and driven by ANS by vagus nerve. It makes up 20% of contractions
What does segmentation do in stomach?
It is more common but weaker, it mixes everything up and moves fluid chyme towards pyloric sphincter and solid chyme move back up. It is less coordinated than peristalsis. It is controlled by a local system- enteric nervous system.
What do gastric chief cells do?
Secretes pepsinogen
What do gastric chief cells have that make them good at their job?
have lots of RER for making proteins
have lots of golgi for packaging and exporting
lots of apical secretion granules for SECRETE
What do parietal cells do?
secrete acid
What do parietal cells have that make them good at their job
Lots of mitochondria for lots of ATP
cytoplasmic tublulovesicles contain H+/K+ ATPase
internal caniculi extend to apical surface
What happens to parietal cells when they are activated?
the tubulovesicles fuse with membrane and microvilli, and project into canaliculi and project into lumen of stomach
what enzyme makes H+ and HCO3-?
Carbonic anhydrase
What kind of environment does pepsinogen need to break down into pepsin?
Acidic
What happens in pyloric antrium?
local peptide hormone - gastrin stimulate histamine release from chromaffin cells that stimulate acid production
What are the phases of gastric selection?
- cephalic
- gastric
- intestinal
What happens in the cephalic phase?
Before food enters the body, it prepares for the food bolus by increasing acid and pepsinogen production. It is a conditioned response to sensory stimuli via the vagus nerve
What happens in the gastric phase?
A powerful local response to local stimuli activating tissue in response via chemo and stretch receptors. The chemoreceptors activate muscles and glands releasing acid, pepsin etc to facilitate digestion. Stomach distention is a central nervous response via the vagus nerve
What happens in the intestinal phase?
The food that is left in the stomach goes into the intestine as chyme and intestines respond to the chemical constituents of chyme and the pH. Signals sent to brain leading to inhibitory (so enterogastric reflux) or excitatory effect (so stomach works harder)
When does an excitatory response happen in the intestinal phase?
When the chyme has a high protein content so the body alerts the stomach it’s not fully breaking down the food and needs to work harder
What hormones have an inhibitory effect on the intestinal phase?
gastric inhibiting peptide
cholecystokinin
secretin
What does omeprazole do?
inhibit histamine binding to receptors on parietal cells
What does ranitidine do?
H+/K+ATPase pump inhibitor
