4.1 Function of the Stomach Flashcards
(23 cards)
What is receptive relaxation?
Vagally mediated relaxation of the orad region (fundus and upper body) which allows food to enter the stomach without raising the intragastric pressure. It prevents food reflux when swallowing.
What is peristalsis?
Coordinated contractions of the stomach to mix the stomach contents
What is ejected from the stomach and how regularly?
Chyme is ejected in liquid form at 3 ‘squirts’ a minute
Why is the stomach acidic?
To unravel proteins
Kill bacteria
Activates proteases
What cell releases HCl?
Parietal cell
What molecules stimulate parietal cells?
Gastrin, histamine and acetylcholine
Where is gastrin secreted from?
G cells
Where are G cells located?
The antrum of the stomach
What are G cells stimulated by?
Peptides in the stomach (Gastrin-releasing peptide (GRP)) Vagal stimulation (acetylcholine)
Where is histamine released from?
Enterochromaffin-like cell (ECL)
What cell releases pepsinogens?
Chief cells
What cells release somatostatin?
D cells
What molecule inhibits gastrin?
Somatostatin
What stimulates somatostatin to be released?
Low pH
How is HCl made in the gut?
Water is split into its ions
The H+ combines with Cl- in the stomach lumen. Cl- is moved out of parietal cells by swapping with HCO3-
What happens to OH- after water has split in the gut?
Combines with CO2 to become HCO3-
This is moved into the blood stream as the alkaline tide
Name the three stages of digestion and the proportion of time spent in each stage
Cephalic (30%)
Gastric (60%)
Intestinal (10%)
What is meant by the ‘cephalic’ stage of digestion?
Smelling, chewing, tasting, swallowing with direct parietal cell stimulation by the vagus nerve. G cells are also stimulated and GRP is released.
What is meant by the ‘gastric’ stage of digestion?
Distention of the stomach stimulates the vagus nerve to stimulate parietal and G cells. Amino acids and peptides also stimulate G cells. Food acts as a buffer in the stomach
What is meant by the ‘intestinal’ stage of digestion?
G cells are inhibited by somatoctatin
How does mucous work to protect the stomach?
Mucous is released by mucous cells in gastric glands. It forms a thick, alkaline layer that sticks to the epithelial cells. This protects the epithelial cells.
Name 3 toxins that damage the stomach wall
Alcohol- dissolves mucous layer
H. pylori- causes acute gastritis
NSAIDs- inhibits prostaglandins
Where does food enter the stomach?
The oesophagus
