医学英语术语1

医学英语术语
Chapter Two Digestive System I．Introduction
The digestive system, also called the alimentary or gastrointestinal tract, begins with the mouth, where food enters the body, and ends with the anus, where solid waste material leaves the body. The primary functions of the organs of the digestive system are threefold.
First, complex food material that is taken into the mouth must be digested, or broken down, mechanically and chemically, as it travels through the gastrointestinal tract (passageway). Digestive enzymes are substances that speed up chemical reactions and help in the breakdown (digestion) of complex nutrients. Complex proteins are digested to simpler amino acids; complicated sugars are reduced to simple sugars, such as glucose; and large fat molecules are broken down to fatty acids and triglycerides.
Second, the digested food must be absorbed into the bloodstream by passing through the walls of the small intestine. In this way, valuable nutrients, such as sugar and amino acids, can travel to all the ceils of the body. Within the cells, nutrients are catabolized (burned) in the presence of oxygen to release energy stored within the food. Amino acid nutrients are used to anabolize (build) large protein molecules that are needed for growth and development of cells. Fatty acids and triglycerides are also absorbed through the walls of the small intestine but enter lymphatic vessels rather than blood vessels. These digested fats eventually enter the blood- stream as lymph vessels join with blood vessels in the upper chest region.
The third function of the digestive system is to eliminate the solid waste materials that cannot be absorbed into the bloodstream. These solid wastes, called feces, are concentrated in the large intestine and finally pass out of the body through the anus.
II. Combining forms
III. Vocabulary
This list will help you review many of the new terms introduced in the text. Short definitions will reinforce your understanding of the terms.。