29 Questions
What is the primary function of tonic contractions in the proximal part of the stomach?
To generate a sustained compressive force that reduces the volume occupied by food
What is the role of rugae in the stomach mucosa?
To allow the stomach to expand as it becomes distended with food and liquid
What type of relaxation is induced in the proximal part of the stomach upon entry of food from the esophagus?
Receptive relaxation
What is the effect of sympathetic stimulation on the force of gastric smooth muscle contractions?
It reduces the force of gastric smooth muscle contractions
What is the primary function of the proximal part of the stomach in gastric motility?
To store food and liquid
Which part of the gastrointestinal tract is the most distensible?
Stomach
What is the primary function of the mucus secreted by mucous cells in the gastric gland?
To protect the gastric mucosa from acid and enzymes
Which type of cells in the gastric gland secrete a hormone that stimulates the parietal cells to secrete hydrochloric acid?
G cells
What is the effect of vagal stimulation on gastrin secretion?
It increases gastrin secretion
What is the mechanism by which gastrin secretion is reduced when a high amount of hydrochloric acid is present in the stomach?
Negative feedback mechanism
What is the primary function of pepsinogen secreted by chief cells in the gastric gland?
To break down proteins into peptides
Into which structure do the secretions from the exocrine cells of the gastric gland flow?
Canaliculus
What is the primary role of carbonic anhydrase in the parietal cells?
To catalyze the formation of carbonic acid from H2O and CO2
What is the net result of the action of the Cl-/HCO3- antiporter in the parietal cell?
Increased concentration of Cl- ions in the parietal cell
What is the purpose of the proton pump (H+/K+ ATPase) in the parietal cell?
To actively transport H+ ions into the stomach lumen
How do HCO3- ions exit the parietal cell?
In exchange for Cl- ions through the Cl-/HCO3- antiporter
What is the characteristic of the gastric juice compared to plasma?
Isotonic
What is the typical pattern of gastric acid secretion throughout the day?
Lower in the morning and higher in the afternoon and evening
Which of the following hormones is produced in the duodenum and inhibits gastric acid secretion?
Secretin
What is the effect of acetylcholine on hydrochloric acid secretion?
Stimulation
What is the primary role of hydrochloric acid in the gastrointestinal tract?
Killing microbes present in the food
Which of the following neurotransmitters inhibits gastric acid secretion?
Somatostatin
Where are the receptors for the five agents that regulate gastric acid secretion located?
Basolateral membrane of parietal cells
At what pH range does gastric lipase operate best?
pH 5-6
Why is gastric lipase important in newborn infants?
Because gastric acid secretion is not fully established
What happens to gastric lipase when it enters the duodenum?
It is inactivated by pancreatic proteases
What is absorbed by the mucous cells of the stomach?
Water, ions, certain drugs, and alcohol
What is the primary function of the stomach in terms of nutrient absorption?
To absorb a small amount of nutrients
In patients with pancreatic insufficiency, what can gastric lipase do?
Partly compensate for the impaired digestion of fat
Test your knowledge of the mechanisms of gastric motility, including the role of sympathetic stimulation, hormones, and smooth muscle cells in the stomach. Learn about the contractile and autorhythmic cells, and the differences in proximal and distal stomach function.
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