课件：医学英语L.9.ppt

Lesson NineWhat We Know About AIDSWhat is HIV? HIV (human immunodeficiency virus) is the virus that causes AIDS. This virus is passed from one perso n to another through blood-to-blood and sexual contact. In addition, infected pregnant women can pass HIV to their baby during pregnancy or delivery, as well as through breast-feeding. People with HIV have what is called HIV infection. Most of these people will develop AIDS as a result of their HIV infection. What is AIDS? What causes AIDS?AIDS stands for acquired immunodeficiency syndrome. An HIV-infected person receives a diagnosis of AIDS after developing one of the CDC-defined AIDS indicator illnesses, (opportunistic infection.) An HIV-positive person who has not had any serious illnesses also can receive an AIDS diagnosis on the basis of certain blood tests (CD4+ counts). A CD4+ count of less than 200 indicates a severely damaged immune system and an AIDS diagnosis. A positive HIV test result does not mean that a person has AIDS. A diagnosis of AIDS is made by a physician using certain clinical criteria. Infection with HIV can weaken the immune system to the point that it has difficulty fighting off certain infections. These types of infections are known as opportunistic infections because they take the opportunity a weakened immune system gives to cause illness. Many of the infections that cause problems or may be life threatening for people with AIDS, are usually controlled by a healthy immune system. The immune system of a person with AIDS is weakened to the point that medical intervention may be necessary to prevent or treat serious illness. Today there are medical treatments that can slow down the rate at which HIV weakens the immune system. There are other treatments that can prevent or cure some of the illnesses associated with AIDS. As with other diseases, early detection offers more options for treatment and preventative care. Also, once a person is diagnosed with AIDS, they will always be considered to have AIDS, regardless of clinical changes later on. For example, if a person has HIV and a CD4 count below 200, they are considered to have AIDS. If their CD4 count later goes back to above 200, they are still considered to have AIDS. Word Formation abbreviation n. From the verb “abbreviate”: write the short form of a word contaminate v. contamination n. contaminant: a substance that can make dirt follicular a. from its noun “folliculus” folliculi pl. dendritic a. from its noun “dendrite” homosexual: homo-: (same) + sexual homobody; homoplastic; homotoxin hetero-: other heteroantibody; heteroantigen; heterostimulation heterotopia; heterotransplantation lymphocytic a. from “lymphocyte” leukocyte: white blood cell erythrocyte: red blood cell thrombocyte: platelet I. Topics for Class Discussion: 1. What is the main idea of Paragraph 1? 2. How is AIDS transmitted? 3. Whats the main idea of Paragraph 3? 4. Who can be easily infected by HIV-1 strain? 5. How is HIV-2 spread? 6. Whats the main idea of Paragraph 5? 7. Whats the main idea of Paragraph 6? 8. How does HIV damage the immune system? 9. Whats the main idea of last paragraph ?II. Language Points: 1. prey to: 1) n. + to (be/ become/ fall prey to): be greatly troubled by e.g. Some people with disordered mind become a prey to fears of being murdered. 2) v. + on e.g. His worries preyed on his mind. Ill health preyed on him for many years. 2. deteriorate v. become worse in quality e.g. Renal function begins to deteriorate. The patients condition has deteriorated since operation. 3. combat v. fight, struggle e.g. The doctors are concentrating their efforts on combating cancers. The inflammatory response is essential in combating most infections. 4. a succession of: e.g. A succession of strange things happened here last month. A succession of cross infections in the ward let him to death. 5. integrate with: combine withe.g. I integrated your suggestion with my plan. The school integrates maths lessons with computer studies. * integrate into: e.g. He tried to integrate all their activities into one program.Human Immunodeficiency Virus (HIV):Overview Human Immunodeficiency Virus (HIV) presents a complex knot for scientists to unravel. After initial contact and attachment to a cell of the immune system (e.g. lymphocytes, monocytes), there is a cascade of intracellular events. The endproduct of these events is the production of massive numbers of new viral particles, death of the infected cells, and ultimate devastation of the immune system.However, the knot IS becoming unraveled. These pages attempt to simplify HIV infection at the cellular level. The following diagram shows a number of steps from initial attachment of a viral particle to a lymphocyte through budding of new viruses from that cell. Attachment to the Lymphocyte Membrane On the surface membrane of all living cells are complex protein structures called receptors. A receptor is often compared to a lock into which a specific key or ligand will fi