VIEWS: 2 PAGES: 6 POSTED ON: 2/27/2013
Jordan Bustard • Where do you think digestion begins? Most people automatically think of the stomach when they think of digestion. Actually, though, digestion starts in the mouth as the first workstation in the digestive process. Food, of course, is ground up by our teeth. We chew without thinking. The jaw muscles pull the jaw up and down, thereby crushing the food and making it softer and smaller. When you are chewing, glands make saliva. Two quarts of saliva are produced each day. Saliva is constantly produced, but more of it is made when we eat. Smelling, seeing, or thinking about food gets the process of making more saliva started. Talk about a mouth-watering meal! • the duodenum, the C-shaped first part • the jejunum, the coiled midsection • the ileum, the final section that leads into the large intestine The inner wall of the small intestine is covered with millions of microscopic, finger- like projections called villi. The villi are the vehicles through which nutrients can be absorbed into the body. • the stomach, food undergoes chemical and mechanical digestion. Here, peristaltic contractions (mechanical digestion) churn the bolus, which mixes with strong digestive juices that the stomach lining cells secrete (chemical digestion). The stomach walls contain three layers of smooth muscle arranged in longitudinal, circular, and oblique (diagonal) rows. These muscles allow the stomach to squeeze and churn the food during mechanical digestion. Powerful hydrochloric acid in the stomach helps break down the bolus into a liquid called chyme. A thick mucus layer that lines the stomach walls prevents the stomach from digesting itself. When mucus is limited, an ulcer (erosion of tissue) may form • Your body does the same thing every day. Hidden throughout your body are dangerous poisons that must be removed in order for it to survive. The process of excretion involves finding and removing waste materials produced by the body. The primary organs of excretion are the lungs, kidneys, and skin. Waste gases are carried by blood travelling through the veins to the lungs where respiration takes place. Dead cells and sweat are removed from the body through the skin which is part of the integument system. Liquid waste is removed from the body through the kidneys. Located beside the spine in your back within your ribcage, the kidneys are small (about 10 centimetres long) reddish-brown organs that are shaped like beans.
Pages to are hidden for
"Digestion _amp; Respiration"Please download to view full document