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Medical and Healthy Living Glossary - V

This page of our online glossary of medical and healthy living is for medical and healthy living terms beginning with the letter 'V'.

• Vaccination - The production of immunity to a disease by inoculation with a vaccine or a specially prepared material that stimulates the production of antibodies. Originally the words vaccination and vaccine applied only to immunisation against smallpox, but they are now used for immunisation against any disease.
• Vaccine - A modified preparation of a bacterium or virus that is no longer dangerous but will stimulate the development of antibodies and therefore provide immunity against actual infection with the disease. Other vaccines consist of specific toxins (e.g. tetanus) or dead bacteria (e.g. cholera and typhoid). Live but weakened organisms are used against smallpox and tuberculosis.
• Valves - Flaps of tissue which opens and closes to allow liquid to pass in one direction only for example, in the heart, blood vessels or lymphatic vessels.
• Vein - A thin-walled vessel that carries deoxygenated blood containing waste carbon dioxide back to the heart.
• Ventricles - A cavity in an organ, such as in the heart or brain. There are two ventricles in the heart, the left ventricle and the right ventricle. There are four ventricles in the brain, each containing cerebrospinal fluid.
• Venule - A small vein or vessel which leads from tissue to a larger vein.
• Verotoxins - Powerful toxins produced by some types of E. coli.
• Villi - Small projections in the intestinal wall that absorb nutrients.
• Virulence - The degree to which a microorganism can cause a disease.
• Viruses - Infectious particles that are the cause of many diseases, ranging from the common cold, flu and chickenpox to herpes, AIDS and polio. Viruses can reproduce only by invading and taking over a living cell. In healthy humans, the invaded cell produces a protein substance called interferon, which prevents the virus from spreading. However, in babies, the elderly and those already weakened by illness or a poor diet, this defence mechanism may not work effectively. Antibiotics have no effect on viruses.