1. The primary function of the GI tract are digestion and the distribution of food.

2. Food enters the GI system at the mouth, where it is chewed and swallowed. Then the food enters the esophagus where the muscle layers move it down to the stomach in a wave like motion known as peristalsis. The esophageal sphincter prevent the food from coming back up. When food reaches the stomach it is temporarily held so that the food can be mechanically and chemically be broken down so it can then be deposited into the small intestine ( duodenum, jejunum, ileum) the duodenum is the first part of the small where bile and pancreatic enzymes enter which continue to breakdown food and transform chime into an alkaline state. Peristalsis then moves down the semi liquid mixture into the jejunum and ileum. The main function of the small intestine is to absorb nutrients from the chime. The large intestine ( cecum, colon, rectum, and anal canal) then receives waste from the small intestine and propels waste toward the anus. The large intestine absorbs water some electrolytes and bile acids. The unabsorbed material becomes fecal matter which is composed of water food residue, microorganisms, digestive secretions, and mucus. As fecal matter accumulates it distends the rectal wall, creating the urge to defecate.

Accessory structures:

There are 3 accessory structures the liver, gall bladder, and pancreas.

LIVER: it forms and releases bile, processes vitamins, proteins, fats, and carbohydrates, stores glycogen, contributes to blood coagulation, metabolizes and biotransforms many chemicals, bacteria, and foreign matter forms antibodies and immunizing substances.

GALLBLADDER: when the bile reaches the gallbladder from the common hepatic duct water and minerals are absorbed to form a more concentrated product. Gallbladder contraction triggered by ingested food causes bile to be released into the cystic duct and the then common bile duct into the duodenum where it aids in the absorption of fats, vitamins, iron and calcium.

PANCREAS: the pancreatic enzymes are released in inactive forms into the duodenum where they are activated. Chapter 50 pg. 809-810 timby

3. The digestive system, also called the gastrointestinal tract, is a passageway that extends through the body like a hallway through a building. Food must be broken down or digested and then absorbed through the walls of the digestive tube before it can actually enter the body and be used by cells. The breakdown of food is both a mechanical and chemical process. Teeth are used for the physical breakdown of food, where salivary amylase begins the chemical digestion of carbohydrates. It is then swallowed and goes through the pharynx by peristalsis. It then enters into the esophagus that leads to the stomach through the esophageal sphincters and into the stomach. Contraction of the stomach’s muscular walls mixes the food thoroughly with gastric juice and breaks it down into a semisolid mixture called chime. It is then passed through the small intestines and absorbs carbohydrates and protein digestion (sugars and amino acids.) After passing through the small intestine and then enters the large intestine and reabsorbs water, salts and vitamins. After going through the process of the large intestine  the substance from the large intestines become fecal matter that is eliminated from the body through the external opening of the anus.

4. The purpose of these wrinkles and projections is to increase surface area for absorption of nutrients. Each villus is covered in microvilli, which increase the surface area manyfold. Each villus contains a lacteal and capillaries. The lacteal absorbs the digested fat into the lymphatic system which will eventually drain into the circulatory system. The capillaries absorb all other digested nutrients.The surface of the cells on the microvilli are covered with a water layer, which has a number of functions in absorption of nutrients.

Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions:

Iron is absorbed in the duodenum Vitamin B12 and bile salts are absorbed in the terminal ileum. Water and lipids are absorbed by passive diffusion throughout Sodium is absorbed by active transport and glucose and amino acid co-transport.Fructose is absorbed by facilitated diffusion.

5. Metabolism- The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.

Resources the Human Body and Health Disease by Thibodeu Patton

American Heritage Dictionary

Inroductory medical-surgical nursing TIMBY

Wikipedia