Upper GI tract structure and function Flashcards
What are 2 reasons for chewing?
Prolong taste experience
Defence against choking
What does the water component of saliva (99%) do?
Softens
What do mucins do?
Part of saliva
Lubricant
What does alpha-amylase do?
Part of saliva as well as other bits of the tract
Catalyses breakdown of polysaccharides into di- and monosaccharides
What do electrolytes do in saliva?
Control tonicity and pH
What do lysozomes do in saliva?
Bacteriocidal
What portion of the oesophagus is has skeletal muscle in ME?
Upper 1/3
What proportion of the oesophagus has smooth muscle?
Lower 2/3
How many layers of muscle are there around the stomach?
3
The ones present along the rest of the tract as well as an oblique layer
How are the stomach muscles supplied?
Via the myenteric plexus
What are the 3 kinds of cells in a gastric gland?
Mucus neck cells
Chief cells
Parietal cells
What kind of cell produces mucus?
Mucus neck cells
What kind of cells produce pepsinogen?
Chief cells
What kind of cells produce HCl?
Parietal cells
What kind of cells produce intrinsic factor?
Parietal cells
What does carbonic anhydrase do?
Converst CO2 and H2O to carbonic acid
How do we get HCl in the stomach lumen?
Cl brought in via transporter with bicarbonate
Carbonic acid donates an H+ ion to become bicarbonate
H+ pumped into stomach lumen via H+/K transporter
What are the main roles of gastric mucus?
Protects from mechanical injury as a result of debris
Protects against acid corrosion
Protects from autodigestion
How does sensing food lead to gastric acid secretion?
Increased vagal tone
G cells activated
G cells produce gastrin
Gastrin acts on parietal cells
Increased vagal tone also causes ACh to act on parietal cells
How are ECL cells linked to gastric acid secretion?
ACh and gastrin may also act on ECL cells which produce histamine which then acts on parietal cells
How does distension lead to gastric acid secretion?
Distension activates vagal/enteric reflexes
Produces ACh which acts on parietal cells
How does the presence of peptides lead to gastric acid secretion?
Peptides in the lumen leads to activation of G cells
G cells produce gastrin
Gastrin acts on parietal cells