gastric juice

Examples of gastric juice in the following topics:

• 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.
  • Chemical stimuli (i.e., partially digested proteins, caffeine) directly activate G-cells (enteroendocrine cells) located in the pyloric region of the stomach to secrete gastrin; this in turn stimulates gastric glands to secrete gastric juice.

• Neural Responses to Food

  • There are three overlapping phases of gastric control: the cephalic phase, the gastric phase, and the intestinal phase.
  • All aspects, such as sight, sense, and smell, trigger the neural responses resulting in salivation and secretion of gastric juices.
  • The gastric phase begins once the food arrives in the stomach.
  • Gastric acids and enzymes process the ingested materials.
  • This phase controls the rate of gastric emptying.

• Vertebrate Digestive Systems

  • As the word monogastric suggests, this type of digestive system consists of one ("mono") stomach chamber ("gastric").
  • The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion.
  • The stomach of birds has two chambers: the proventriculus, where gastric juices are produced to digest the food before it enters the stomach, and the gizzard, where the food is stored, soaked, and mechanically ground.
  • This is where gastric juices are secreted.
  • Food passes from the crop to the first of two stomachs, called the proventriculus, which contains digestive juices that break down food.

• Processes and Functions of the Digestive System

  • Pancreatic juices are excreted into the digestive system to break down complex molecules such as proteins and fats.
  • Once the bolus reaches the stomach, gastric juices mix with the partially digested food and continue the breakdown process.
  • The stomach is a muscular bag that maneuvers food particles, mixing highly acidic gastric juice and powerful digestive enzymes with the chyme to prepare for nutrient absorption in the small intestine.
  • Stimulatory hormones such as gastrin and motillin help the stomach pump gastric juice and move chyme.

• 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 System: Mouth and Stomach

  • The stomach, a saclike organ, secretes gastric digestive juices.
  • Another cell type, parietal cells, secrete hydrogen and chloride ions, which combine in the lumen to form hydrochloric acid, the primary acidic component of the stomach juices.
  • The partially-digested food and gastric juice mixture is called chyme.
  • Gastric emptying occurs within two to six hours after a meal.

• Pancreatic Juice

  • Pancreatic fluid or juice contains digestive enzymes that pass to the small intestine where they help to further break down the carbohydrates, proteins, and lipids (fats) in the chyme.
  • Pancreatic juice is alkaline in nature due to the high concentration of bicarbonate ions.
  • This is useful in neutralizing the acidic gastric acid, allowing for effective enzymic action.
  • Pancreatic juice secretion is regulated by the hormones secretin and cholecystokinin.
  • Pancreatic duct rupture and pancreatic juice leakage cause pancreatic self-digestion.

• Digestive Properties of the Stomach

  • Gastric ulcers can be healed by supplemental daily doses of Epidermal growth factor (EGF).
  • Cholecystokinin (CCK) primarily effects the gall bladder, causing it to contract, but it also decreases gastric emptying and increases release of pancreatic juice, which is alkaline and neutralizes the chyme.
  • Gastric inhibitory peptide (GIP) decreases both gastric acid release and motility.
  • Enteroglucagon decreases both gastric acid and motility.
  • There are many different gastric glands which secrete many different chemicals.

• 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 .
  • Histamine is a paracrine secretion from the enteroendocrine cells in the gastric glands.
  • During the gastric phase, gastrin is secreted.

• 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.
  • Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum .
  • 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.