gastric phase

Examples of gastric phase in the following topics:

• Gastric Phase

  • The gastric phase is a period in which swallowed food activates gastric activity in the stomach.
  • The gastric phase is a period in which swallowed food and semidigested protein (peptides and amino acids) activate gastric activity.
  • About two-thirds of gastric secretion occurs during this phase .
  • Below pH of two, stomach acid inhibits the parietal cells and G cells: a negative feedback loop that winds down the gastric phase as the need for pepsin and HCl declines.
  • During the gastric phase, gastrin is secreted.

• Neural Responses to Food

  • There are three overlapping phases of gastric control: the cephalic phase, the gastric phase, and the intestinal phase.
  • The gastric and salivary secretion in the cephalic phase can also take place at the thought of food.
  • The gastric phase begins once the food arrives in the stomach.
  • The gastric phase is stimulated by (1) distension of the stomach, (2) a decrease in the pH of the gastric contents, and (3) the presence of undigested material.
  • This phase controls the rate of gastric emptying.

• Cephalic Phase

  • The cephalic phase of gastric secretion occurs even before food enters the stomach via neurological signals.
  • The cephalic phase of gastric secretion occurs even before food enters the stomach, especially while it is being eaten.
  • Neurogenic signals that initiate the cephalic phase of gastric secretion originate from the cerebral cortex, and in the appetite centers of the amygdala and hypothalamus.
  • This phase of secretion normally accounts for about 20 percent of the gastric secretion associated with eating a meal.
  • Cephalic phase causes ECL cells to secrete histamine and increase HCl acid in the stomach.

• Hormonal Responses to Food

  • During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins.
  • In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase.
  • A hormone called gastric inhibitory peptide is secreted by the small intestine to slow down the peristaltic movements of the intestine to allow fatty foods more time to be digested and absorbed.

• Intestinal Phase

  • The intestinal phase occurs in the duodenum, responds to arriving chyme, and moderates gastric activity via hormones and nervous reflexes.
  • The intestinal phase is the stage of digestion in which the duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes.
  • The duodenum initially enhances gastric secretion, but soon inhibits it.
  • Originally called gastric-inhibitory peptide, it is no longer thought to have a significant effect on the stomach.
  • The intestinal phase of digestion occurs in the duodenum, the first segment of the small intestine.

• Vomiting

  • Gastric vomiting leads to the loss of acid and chlorine directly.
  • The vomiting act has two phases.
  • In this retching phase nothing has yet been expelled.
  • Gastric secretions and likewise vomit are highly acidic.
  • Recent food intake appears in the gastric vomit.

• Peptic Ulcer Disease

  • Rarely, an ulcer can lead to a gastric or duodenal perforation, which leads to acute peritonitis.
  • The gastric mucosa protects itself from gastric acid with a layer of mucus, the secretion of which is stimulated by certain prostaglandins.
  • Younger patients with ulcer-like symptoms are often treated with antacids.The ability of antacids to neutralize acidity by increasing the pH or blocking the secretion of acid by gastric cells is critical in reducing acidity in the stomach.
  • This gastric ulcer was found in tissue removed during a gastrectomy.
  • This endoscopic image shows a gastric ulcer, which upon biopsy was shown to be gastric cancer.

• Gross Anatomy of the Stomach

  • A mucous membrane lines the stomach which contains glands (with chief cells) that secrete gastric juices.
  • The gastric glands begin secreting before food enters the stomach due to the parasympathetic impulses of the vagus nerve, making the stomach also a storage vat for that acid.
  • The arteries supplying the stomach are the left gastric, the right gastric and right gastroepiploic branches of the hepatic, and the left gastroepiploic and short gastric branches of the lineal.
  • The arteries break up at the base of the gastric tubules into a plexus of fine capillaries, which run upward between the tubules.

• Digestive Properties of the Stomach

  • Gastric ulcers can be healed by supplemental daily doses of Epidermal growth factor (EGF).
  • Gastric inhibitory peptide (GIP) decreases both gastric acid release and motility.
  • Enteroglucagon decreases both gastric acid and motility.
  • The biological effects of salivary EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, and stimulation of DNA synthesis as well as mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin, and to physical, chemical, and bacterial agents.
  • There are many different gastric glands which secrete many different chemicals.

• Interpreting Phase Diagrams

  • The lines that separate these single phase regions are known as phase boundaries.
  • By focusing attention on distinct single phase regions, phase diagrams help us to understand the range over which a particular pure sample of matter exists as a particular phase.
  • When evaluating the phase diagram, it is worth noting that the solid-liquid phase boundary in the phase diagram of most substances has a positive slope.
  • With a knowledge of the major components of phase diagrams and the features of phase plots, a phase diagram can be used to understand how altering thermodynamic parameters influences the states/phases of matter a sample of a substance is in.
  • A typical phase diagram illustrating the major components of a phase diagram as well as the critical point.