关于消化系统的英文ppt课件.ppt

The Digestive System(also called the gastrointestinal or alimentary canal) The primary functions Ingestion Digestion Absorption Elimination Introduction Anatomically, the digestive system consist of a 30-foot long, mucous membrane-lined tube beginning with mouth and ending with the anus The digestive system Mouth Pharynx Esophagus Stomach Small intestine Large intestine Liver Gallbladder Pancreas Accessory organs of the digestive system The oral cavity The teeth The tongue The palate Chewing and swallowing The teeth are used to cut ,tear and crush food into smaller pieces. Each tooth consists of pulp, cementum and enamel.The teeth are classified incisors , cuspids and molars. The tongue manipulates food in the mouth during mastication and deglutition. The palate the hard plate and the soft plate (the uvula hanging from the soft plate) The pharynx or throat ,is a long muscular tube that serves as a passageway for food from the mouth to the esophagus and as a passway for air from nose to the windpipe. The esophagus is a long muscular tube extending from the pharynx to the stomach .Food is propelled by rhythmic contractions of muscles in the wall of the esophagus. This process is called peristalsis. The stomach It is composed of an upper portion called fundus,a middle section known as the body and a lower portion, called the antrum. The cardiac sphincter relaxes and contracts to move food from the esophagus into the stomach ,whereas the pyloric sphincter allows food to leave the stomach when it sufficiently digested. As the stomach fills ,the rugae unfolded, exposing the digestive glands and stimulating them to secret digestive enzymes and hydrochloric acid. These substances help transform food present to a semifluid substance. The small intestine is the region of the gut where nearly all of the chemical digestion of the nutrition components of food take place. It divided into 3 sections:1)the duodenum 2)t