16 Questions
What percentage of gastric secretion is attributed to the cephalic phase of digestion?
20 percent
What triggers the cephalic phase of gastric secretion?
The sight, smell, thought or taste of food
What is the primary function of hydrochloric acid in the stomach?
To lower the pH and break apart food
What is the term for the thick, semi-liquid mass of partly digested food that is passed from the stomach to the duodenum?
Chyme
During the gastric phase, what stimulates gastric activity?
The stretching of the stomach wall
What is the primary function of the gastric phase of digestion?
To break apart food into smaller molecules
What is the initial response of the duodenum to the arrival of chyme?
It enhances gastric secretion
What is the primary role of gastrin in the digestive process?
To stimulate gastric activity
What is the primary function of gastrin in the stomach?
To stimulate the secretion of pepsinogen and hydrochloric acid
What is the role of enteroendocrine cells in the intestine?
To produce hormones that regulate the digestive system
What is the effect of chyme entering the duodenum on gastric secretion and motility?
It suppresses gastric secretion and motility
What is the function of secretin in the duodenum?
To stimulate the secretion of sodium bicarbonate in the pancreas and bile in the liver
What is the role of the enterogastric reflex?
To suppress gastric secretion and motility
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
How does the stretching of the duodenum affect gastric function?
It enhances gastric function via the vagal nerve
How many main hormones are involved in the regulation of the digestive system?
5
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.
Learn about the different phases of digestion, including the cephalic phase and gastric phase, and how they contribute to the breakdown of food.
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