Digestion
The Gastrointestinal (GI) tract is an organization of numerous organs that take in food, and through numerous processes digest it to retrieve the nutrients. The GI tract has various functions including, ingestion, digestion, absorption, and defecation. In human beings the GI tract is more or less 6.5 meters (20 feet) long. The GI tract consists of the following, mouth, pharynx, esophagus, and stomach.
Extracellular is the route by which humans digest their food. There are many digestive enzymes that are secreted from cells lining the inner surfaces of various exocrine glands. These enzymes are used to hydrolyze the larger molecules that are found in food into smaller more soluble and usable molecules.
Lets start off with ingestion. Ingestion is the process by which an individual places food inside their mouth, and using their teeth grind the food into smaller particles. The food is then moistened and lubricated by saliva, which is secreted by the parotid, sublingual, and sub-mandibular glands. Starch is digested by amylase, which is found in saliva, and then the individual swallows the food into the esophagus it goes. From the esophagus to the stomach it is aided by peristalsis.
Once the bolus of food reaches the stomach, there will be approximately 400-800 ml of gastric juice that is present with each meal. The millions of gastric glands that are found lining the wall of the stomach produce the gastric juice. There are numerous cells that are present in the gastric glands and they include
• Parietal cells
• Chief cells
• Mucus-secreting cells
• Hormone secreting cells
Parietal cells main secretion product is hydrochloric acid and intrinsic factor. Parietal cells contain a H+ ATPase, and this protein secretes H+ ions using ATP energy, and the mixture of H+ ions and the gastric juice gives the pH to be less than 1.
The intrinsic factor is a protein and its function is to bind ingested vitamin B12, and position it to be taken in or absorbed by the...
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