DIGESTION OF CARBOHYDRATES
Digestion of carbohydrate begins in the mouth, with the secretion of the enzyme salivary amylase from the serous cells of the salivary gland. This enzyme breaks starch and glycogen into disaccharides. The mucous cells of the salivary gland secrete a mucus, which causes the food to stick together, and acts as a lubricant to aid in swallowing. The salivary glands are grouped into three categories: the parotid gland, submandibular glands, and sublingual, all located near the mouth. The food (bolus) is forced into the pharynx by the tongue. As the food is swallowed, it moves into the esophagus (a straight collapsible tube), which essentially provides a passageway from the pharynx to the stomach. The mucous glands of the esophagus secrete mucus to aid in moistening and lubricating the bolus. The bolus passes through the cardiac sphincter, into the first section of the stomach. The stomach is divided into several regions: the cardiac region, body region, fundic region, and pyloric region. The stomach works to mix and churn the food, which aids in further digestion of carbohydrates. At this point, the bolus is converted into a semifluid paste of bolus and gastric juices called chyme.
The chyme then travels through the pyloric sphincter into the first section of the small intestines. The small intestines is divided into three sections: the duodenum, jejunum, and ileum. The majority of digestion of carbohydrates takes place in the small intestines. As the chyme moves into the duodenum, an enzyme called pancreatic amylase is released through the pancreatic duct. This enzyme splits molecules of starch and glycogen into disaccharides.
The liver plays an important role in the several metabolic activities. It is responsible for changing glycogen to glucose to increase blood glucose or converting glucose to glycogen, thereby decreasing blood glucose. The liver also converts other noncarbohydrates into glucose, if needed....
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