Phases of Digestion

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Questions and Answers

What percentage of gastric secretion is attributed to the cephalic phase of digestion?

10 percent

80 percent

50 percent

20 percent (correct)

What triggers the cephalic phase of gastric secretion?

The release of gastrin

The swallowing of food

The sight, smell, thought or taste of food (correct)

The presence of food in the stomach

What is the primary function of hydrochloric acid in the stomach?

To break down carbohydrates

To lower the pH and break apart food (correct)

To stimulate gastric activity

To release gastrin

What is the term for the thick, semi-liquid mass of partly digested food that is passed from the stomach to the duodenum?

Chyme Signup and view all the answers

During the gastric phase, what stimulates gastric activity?

The stretching of the stomach wall Signup and view all the answers

What is the primary function of the gastric phase of digestion?

To break apart food into smaller molecules Signup and view all the answers

What is the initial response of the duodenum to the arrival of chyme?

It enhances gastric secretion Signup and view all the answers

What is the primary role of gastrin in the digestive process?

To stimulate gastric activity Signup and view all the answers

What is the primary function of gastrin in the stomach?

To stimulate the secretion of pepsinogen and hydrochloric acid Signup and view all the answers

What is the role of enteroendocrine cells in the intestine?

To produce hormones that regulate the digestive system Signup and view all the answers

What is the effect of chyme entering the duodenum on gastric secretion and motility?

It suppresses gastric secretion and motility Signup and view all the answers

What is the function of secretin in the duodenum?

To stimulate the secretion of sodium bicarbonate in the pancreas and bile in the liver Signup and view all the answers

What is the role of the enterogastric reflex?

To suppress gastric secretion and motility Signup and view all the answers

What is the primary function of cholecystokinin (CCK) in the duodenum?

To stimulate the release of digestive enzymes in the pancreas and the emptying of bile from the gall bladder Signup and view all the answers

How does the stretching of the duodenum affect gastric function?

It enhances gastric function via the vagal nerve Signup and view all the answers

How many main hormones are involved in the regulation of the digestive system?

5 Signup and view all the answers

Study Notes

Phases of Digestion

The cephalic phase of digestion begins when food is seen, smelled, thought of, or tasted, and accounts for about 20% of gastric secretion associated with eating a meal.
During the cephalic phase, the stomach secretes hydrochloric acid and pepsin, which are digestive juices, due to neurological signals.

Gastric Phase

The gastric phase is the second phase of digestion that follows mastication (chewing) and takes place in the stomach.
In this phase, swallowed food activates gastric activity in the stomach, which releases gastrin, and accounts for about two-thirds of gastric secretions.
The stomach wall stretches as food enters it through the cardiac sphincter, stimulating gastric activity by stretching the stomach and raising the pH of its contents.
Gastric secretion is stimulated chiefly by three chemicals: acetylcholine (ACh), histamine, and gastrin.

Intestinal Phase

The intestinal phase occurs in the duodenum as a response to arriving chyme, and moderates gastric activity via hormones and nervous reflexes.
The duodenum initially enhances gastric secretion, but soon inhibits it, and stretching of the duodenum enhances gastric function via the vagal nerve.
The enterogastric reflex is triggered by the acid and semi-digested fats in the duodenum, sending inhibitory signals to the stomach by way of the enteric nervous system.

Hormones of the Digestive System

There are five main hormones that aid and regulate the digestive system: gastrin, secretin, cholecystokinin, gastric inhibitory peptide, and motilin.
Gastrin stimulates the gastric glands to secrete pepsinogen and hydrochloric acid in the stomach.
Secretin signals the secretion of sodium bicarbonate in the pancreas and stimulates the secretion of bile in the liver.
Cholecystokinin (CCK) stimulates the release of digestive enzymes in the pancreas and the emptying of bile from the gallbladder.