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Gastric activity involved in digestion is divided into three phases of digestion known as the cephalic phase, the gastric phase, and the intestinal phase. These phases overlap and all three can occur simultaneously. [1] A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase).
Gastric acid or stomach acid is the acidic component – hydrochloric acid of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other animals, but is very similar to that of carrion eating carnivores , needing protection from ingesting pathogens .
A canaliculus is an adaptation found on gastric parietal cells. It is a deep infolding, or little channel, which serves to increase the surface area, e.g. for secretion. The parietal cell membrane is dynamic; the numbers of canaliculi rise and fall according to secretory n
During hydrochloric acid secretion in the stomach, the gastric parietal cells extract chloride anions, carbon dioxide, water and sodium cations from the blood plasma and in turn release bicarbonate back into the plasma after forming it from carbon dioxide and water constituents. This is to maintain the plasma's electrical balance, as the ...
A peptide hormone, gastrin, produced by G cells in the gastric glands, stimulates the production of gastric juice which activates the digestive enzymes. Pepsinogen is a precursor enzyme produced by the gastric chief cells, and gastric acid activates this to the enzyme pepsin which begins the digestion of proteins. As these two chemicals would ...
The major processes that occur in the GI tract are: motility, secretion, regulation, digestion and circulation. The proper function and coordination of these processes are vital for maintaining good health by providing for the effective digestion and uptake of nutrients.
There are two types of gastric gland, the exocrine oxyntic gland, and the endocrine pyloric gland. The major type of gastric gland is the oxyntic gland that is present in the fundus and the body of the stomach making up about 80 per cent of the stomach area. These glands are often referred to simply as the gastric glands.
Serous glands: These glands produce a secretion rich in water, electrolytes, and enzymes. A great example of a serous oral gland is the parotid gland. Mixed glands: These glands have both serous cells and mucous cells, and include sublingual and submandibular glands. Their secretion is mucinous and high in viscosity.