The process of digestion occurs in a long tube called alimentary canal.Here,the food enters the alimentary canal.
Good health depends upon not only good food but also good digestion and absorption. Without good digestion and absorption, the health giving nutrients of our food cannot be optimally used by the body. Therefore, before we can begin to appreciate the nutritive qualities of food, we must first appreciate and understand the organs of the body that are involved with digestion and the process of digestion itself.
The Organs of Digestion
The alimentary canal is a coiled tube about thirty feet long that passes through the center of the body. It extends from the mouth to the anus and includes the mouth, esophagus, stomach, small intestine, and large intestine or colon. The alimentary canal, together with its accessory organs, the liver, gallbladder, and pancreas, make up the digestive tract. The purpose of the digestive tract is to perform chemical and mechanical digestion, absorption, waste storage, and excretion.
The Process of Digestion
Digestion is a series of physical and chemical changes by which food taken into the body undergoes hydrolysis (addition of water) and is broken down in preparation for absorption from the digestive tract into the bloodstream. Digestion takes place in the alimentary canal. In the upper section of the tract, mechanical digestion is accomplished by the chewing and grinding of food into smaller pieces, which are then pushed along the digestive tract. At appropriate times the food is mixed with digestive juices that cause chemical changes that break down the food into smaller absorbable compounds. At the lower end of the canal, waste products are stored and periodically eliminated from the body.
Why does the aroma of certain foods make my mouth water?
When the brain perceives food, it signals the digestive system that food is on its way. The smell, taste, and sometimes even the thought of food trigger the three pairs of salivary glands to produce saliva. These glands are located under the tongue (sublingual), under the jaw (submandibular), and in front of the ears (parotid). Saliva acts as a wetting agent. It moistens and lubricates food, making it easier to swallow. It also contains carbohydrate cleaving digestive enzyme amylase. The average person secretes up to three pints of saliva a day.
How does food move through the digestive tract?
Muscle power, not gravity, moves the food through the alimentary canal. The wall of this tube contain two layers of muscles. One set, the circular muscle layer, encircles the tube, while the other, the longitudinal layer, runs lengthwise along the tube. When food is swallowed, the muscles are stimulated, causing peristalsis, waves of muscle contractions. Peristalsis waves quickly move the food to the stomach. These waves continue until the esophagus is emptied of food.