Biochemistry - gastric secretion

What is the primary function of hydrochloric acid (HCl) in gastric secretions?

HCl creates an acidic environment for activating pepsinogen, digesting proteins, and killing ingested microorganisms.

What is intrinsic factor and why is it important?

Intrinsic factor is a glycoprotein secreted by parietal cells that is essential for the absorption of vitamin B12 in the small intestine.

What do chief cells secrete and what are their functions?

Chief cells secrete pepsinogen and gastric lipase; pepsinogen gets activated to pepsin for protein digestion, and gastric lipase initiates fat digestion.

Describe the mechanism of HCl secretion in the stomach.

1. CO2 and Cl- enter the parietal cells. 2. CO2 forms carbonic acid (H2CO3) which dissociates to H+ and HCO3-. 3. H+ is secreted into the gastric lumen while Cl- exits the parietal cell into the lumen, combining with H+ to form HCl.

What is the role of gastric mucus?

Gastric mucus protects the stomach lining from acid and mechanical damage by providing a viscous, alkaline barrier.

Which cells in the stomach secrete gastrin hormone and what does this hormone do?

G cells secrete gastrin; it stimulates parietal cells to produce HCl and promotes pepsinogen release from chief cells.

What are the types of cells found in the gastric glands?

The gastric glands contain parietal cells, chief cells, mucous cells, and endocrine cells.

What is the pH level of gastric juice and what does it indicate?

The pH level of gastric juice ranges from 1 to 3, indicating a highly acidic environment conducive for digestion.

What is the daily secretion volume of gastric juice?

Approximately 2 to 3 liters of gastric juice is secreted daily.

How does bicarbonate function in the gastric secretion process?

Bicarbonate helps to neutralize gastric acid near the stomach lining, protecting the epithelial cells from acid damage.

What is the role of pepsin in digestion?

Pepsin is an enzyme that digests proteins into smaller peptides in the acidic environment of the stomach.

What triggers the release of gastrin?

The release of gastrin is triggered by the presence of food in the stomach, especially proteins.

How do proton pump inhibitors work?

Proton pump inhibitors block the proton pump in parietal cells, reducing HCl production and lowering stomach acidity.

What is the significance of the pH of gastric juice?

The low pH (1-3) of gastric juice is crucial for activating digestive enzymes and killing pathogens.

What are the effects of high acidity on gastric lining?

High acidity can lead to damage of the gastric lining and conditions such as gastritis or ulcers.

What are mucous cells responsible for in the stomach?

Mucous cells secrete mucus that protects the stomach lining from acid and mechanical injury.

What is the function of gastric lipase?

Gastric lipase initiates the digestion of fats in the stomach.

What factors can increase gastric acid secretion?

Factors that can increase gastric acid secretion include stress, consumption of spicy foods, and certain medications.

What is the difference between endocrine and exocrine secretions in the stomach?

Endocrine secretions, like gastrin, enter the bloodstream, whereas exocrine secretions, like HCl, are released into the gastric lumen.

How does the stomach protect itself from its own acidic environment?

The stomach protects itself through the secretion of mucus and bicarbonate, creating a barrier between the acid and the gastric epithelium.