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Chemical Digestion Stomach The pyloric sphincter at the bottom of the stomach governs the passage of food out of the stomach into the small intestine.About 10 inches down the esophagus, the swallowed food or bolus is now fairly well minced and turned into a pulpy mass as it passes into the stomach. The function of the stomach is best described as a food processing unit (similar to one you may have in your kitchen) and a storage cistern. The stomach is both chemical and mechanical. Various chemicals in the stomach like the digestive enzymes pepsin, rennin, and lipase interact to break down the food. In addition, hydrochloric acid creates suitable environment for the enzymes and assists in the digestion. Also, the watery mucus provides a protective lining for the muscular walls of the stomach so it will not be digested by the acid or enzymes. The mechanical action of the muscles in the stomach constrict and relax in a continuous motion blending, whipping, and stirring the stomach's contents into chyme, a pulpy substance that can be handled by the small intestine. Small intestine The small intestine is the longest organ of the digestive tract. It is divided up indiscriminately into three sections: the duodenum, the jejunum, and the ilium. Duodenum This is the place where the ultimate destruction of food digestion reaches its completion and where the acidity of chyme is nullified. Enzymes are secreted by the walls of the duodenum and unite with the pancreatic enzymes in the duodenum. Jejunum Peristalsis pushes the nutrient liquid out of the duodenum into the first reaches of the jejunum. A greater number of villi, microscopic, hair like structures, begin to absorb substances from the digested contents of the small intestine, turns them into thin watery liquid and starts them on their way to other parts of the body. Ilium This is the place which is about a third of the small intestine. The greatest number of the estimated five or six million villi in the small intestine are found along the ilium making it the main absorption locale of the gastrointestinal tract. The Liver, Gallbladder, and Pancreas Legitimately, these three organs lie outside of the gastrointestinal tract. Nevertheless, digestive fluids from all three meet like intersections of a railway track at the common bile duct, and their movement from there into the duodenum is controlled by a sphincter muscle. The pancreas is a producer of digestive enzymes. The gallbladder is a small reservoir for bile. The liver reproduces nutrients so that they can be used for cell-rebuilding and energy. Large Intestine There is a merger between the ilium and the cecum, the first section of the large intestine. What the cecum primarily inherits is water. What the large intestine essentially does, other than act as a passageway for removal of body wastes, is to act as a provisional reservoir for water. There are no villi in the large intestine and peristalsis is much less forceful than in the small intestine. As water is absorbed, the contents of the large intestine change from a watery liquid and are compressed into semisolid feces. Nerve endings in the large intestine signal the brain that it is time for a bowel movement. The fecal material moves through the colon down to several remaining inches known as the rectum and out through the anus an opening controlled by the outlet valves of the large intestine. Enzymes and Other Secretions Site of Enzyme Enzyme Origin Nutrient It Breaks Down Salivary Glands Salivary Amylase Carbohydrates-sugars Simple Sugars Mouth Gastric glands Pepsin Proteins Amino Acids Stomach Liver Bile Fats/Lipids Emulsified Fats Small Intestine Small Intestine Maltase, Lactase, Sucrase Carbohydrates Simple sugars Small Intestine Pancreas Proteins, Fats/Lipids, Carbohydrates Amino acids, Glycerol/Fatty Acids, Simple Sugars Small Intestine Trypsin, Lipase, Amylase Product Of Enzyme Action Place of Enzyme Action Mechanical Digestion Mechanical Digestion begins in the mouth, where the saliva, teeth, and tongue all play an important role in this digestive process and it ends in the stomach. Mouth The MOUTH contains the tongue which is covered with tiny projecting papillae through which are conveyed sensations of taste and touch; the teeth; and the salivary glands, which secrete saliva. The process of digestion starts in the mouth. Food is masticated (chewed) by the teeth, moistened by the saliva, which contains important chemical substances for changing it, and rolled by the tongue. It is then pushed backward by the tongue into Pharynx The PHARYNX is a funnel-shaped opening which is a continuation of the mouth. The food then passes down the smallest taste, smell, and anticipation of food sends signals to the brain. The brain in turn sends messages to a system of salivary glands. Saliva is essentially made up of water and begins to soften up the food so it can pass more smoothly down the throat. Besides water there is also a very special substance, an enzyme called ptyalin, whose main task is to breakdown the food into simpler forms. Esophagus This is a very elastic, muscular tube about eight to ten inches (18 to 25 cm) long. The food is forced onward by the involuntary contractions of the muscles in the esophagus. It passes from the esophagus into the stomach. Movements After ingestion and mastication, the food particles move from the mouth into the pharynx, then into the esophagus. This movement is deglutition, or swallowing. Mixing movements occur in the stomach as a result of smooth muscle contraction. These repetitive contractions usually occur in small segments of the GI tract and mix the food particles with enzymes and other fluids. The movements that propel the food particles through the GI tract are called peristalsis. Peristalsis This mechanical action has to do with sets of muscles that cooperate to move both liquid and solid food along the digestive tract. In other word, it pushes food along your esophagus, stomach, and intestine... Gravitational pull is lessened in a sense when food enters the esophagus because of peristalsis. Peristalsis helps a person to swallow lying down or even standing on their head. Peristalsis has another essential task besides assisting in the movement of food through the body. It also helps to knead, agitate, and pound the solid residue that is left after the teeth or those without teeth, the gums, have done their best. These are rhythmic waves of contractions that move the food particles through the various regions in which mechanical and chemical digestion takes place. Digestive System The organ system includes the gastrointestinal tract (GI tract) and its accessory organs. The digestive system processes food into molecules that can be absorbed and utilized by the cells of the body. Food is broken down, bit by bit, until the molecules are small enough to be absorbed and the waste products are eliminated. The gastrointestinal (GI) tract, also called the digestive tract, alimentary canal, or gut, consists of a long continuous tube that extends from the mouth to the anus. It includes the following regions: mouth pharynx esophagus stomach small intestine large intestine rectum anus The tongue and teeth are accessory structures located in the mouth. The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion. These organs secrete fluids into the GI tract. Food undergoes three types of processes in the body: digestion absorption elimination Digestion and absorption occur in the GI tract. After the nutrients are absorbed, they are available to all cells in the body and are utilized by the body cells in metabolism.