Digestive Process :: essays research papers

Digestive Process Digestive Process It is in the mouth, that the Thanksgiving feast begins its journey through the fabulous digestive system. It is here that the lips, cheeks and tongue, carefully position the food that the teeth will chew. This chewing process breaks up the food, this being a part of mechanical digestion. While the teeth grind up the turkey and tasty stuffings, the salivary glands begin emitting enzymes, these enzymes being contained in saliva. This saliva helps to dissolve some foods, and adds mucus to make the food's passage through the digestive system a little more "speedy". The saliva also attacks dangerous microorganisms which enter the mouth. Saliva also contains an enzyme which helps to break down carbohydrates into sugars. As the food is being ground and coated with saliva, it's passed over the taste buds, which in turn send messages to the brain. The brain uses this information to decide whether or not the food should be swallowed. The food is then gathered into a ball, cal led a bolus, and it is pushed down into the pharynx by way of the tongue. This bolus of "Thanksgiving meal" is then passed down the esophagus, the esophagus being a 24cm long tube which connects the pharynx and stomach. Lining the walls of the esophagus are rings of muscle which contract in waves, pushing the bolus down the length of the esophagus. At the base of the esophagus, where the esophagus and stomach join, a thick ring of muscle called a sphincter, is found. This sphincter acts like a valve, as it allows food to pass into the stomach but does not permit it to pass back up through the esophagus. The stomach, which is in the essence a large muscle sack, contains three sets of glands which produce gastric fluids. One set produces mucus which coats the food, making it slippery, and it protects the stomach walls from being digested by its own secretions. The second set of manufactures hydrochloric acid, which aids in the "break-down" of foods. In conjuction with hydrochloric aci d, pepsin, which aids in the "break-down" of protein into smaller polypeptides, begins the process of protein digestion. The stomach's muscular walls move around the "food" and mucus, mixing them with the gastric fluids produced. The "food" becomes a pasty substances referred to as chyme, after about 2 or 3 hours of grinding within the stomach.