Infection

-
Infection, injurious contamination of the body or part of the body by pathogenic agents, such as fungi (see Fungus Infections), bacteria, protozoa, rickettsiae, or viruses, or by the toxins that these agents may produce. An infection may be local and confined to one area or generalized and spread throughout the body. Once the infectious agent enters the host and begins to proliferate, the defense mechanisms of the body react to the infection, producing the characteristic symptoms of pain, swelling, reddening at the site of infection, functional disorders, rise in body temperature and pulse rates, and an increase in the number of white cells (see Immune System).

Infectious agents may enter the body of the host by several routes. The most common route is through the respiratory passages, urinary tract, and gastrointestinal tract, but other common entry routes are through the skin, especially injured skin, the mucosal surfaces of other body openings, and the conjunctiva of the eyes. Pregnant mothers may also transmit infections to their fetuses. The degree of infection is related to the dose and virulence of the infecting agent, as well as to the resistance or immunity of the host against that organism. Resistance to infection is lowered by many diseases of the immune system, leukemia, and cancer, as well as by conditions such as severe burns or malnutrition. In healthy people, the body's own so-called natural flora of bacteria form a line of defense against mild infections, which may thus be taken care of without further treatment. Antibiotics such as sulfa drugs and other pharmaceuticals are used against more severe infections, and vaccines serve as preventive measures against a wide range of infectious diseases (see Immunization).

Among the many infectious diseases are the common cold, chicken pox, cholera, diphtheria, German measles, influenza, malaria, mumps, rabies, tuberculosis, and sexually transmitted infections. See also Disease.

Comments

Post a Comment

Popular posts from this blog

Cream, Butter, and Ice Cream

-
. In order for a product to be labeled as cream, it must contain 18 percent milk fat or more. Light whipping cream must contain at least 30 percent fat, and 36 percent fat is the minimum fat content for heavy whipping cream. Half-and-half, an equal mixture of both milk and cream, must have at least 10.5 percent fat. The various grades of cream are valued for their smooth, thick texture. They are often used in cooking instead of milk, because they are less likely to form a skin when heated and can be whipped into a stiff foam. When chilled cream is churned gently, the fat globules gather together to form butter, leaving buttermilk as the by-product. Butter contains at least 82.5 percent fat. In the past, before the advent of widespread refrigeration, salt was added to butter to retard bacterial spoilage; now salt is added mainly for flavor. Ice cream, a popular frozen dessert, is made of milk, cream, sugar, and flavoring. The mixture is slowly beaten while chilled until it is partially ...
Read more

Deoxyribonucleic Acid

-
Deoxyribonucleic Acid (DNA), genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct protein synthesis and replication. Protein synthesis is the production of the proteins needed by the cell or virus for its activities and development. Replication is the process by which DNA copies itself for each descendant cell or virus, passing on the information needed for protein synthesis. In most cellular organisms, DNA is organized on chromosomes located in the nucleus of the cell .
Read more

Bacteria

-
Bacteria is a one-celled organisms visible only through a microscope. Bacteria live all around us and within us. The air is filled with bacteria, and they have even entered outer space in spacecraft. Bacteria live in the deepest parts of the ocean and deep within Earth. They are in the soil, in our food, and on plants and animals. Even our bodies are home to many different kinds of bacteria. Our lives are closely intertwined with theirs, and the health of our planet depends very much on their activities. Bacterial cells are so small that scientists measure them in units called micrometers (µm). One micrometer equals a millionth of a meter (0.0000001 m or about 0.000039 in), and an average bacterium is about one micrometer long. Hundreds of thousands of bacteria would fit on a rounded dot made by a pencil. Bacteria lack a true nucleus, a feature that distinguishes them from plant and animal cells. In plants and animals the saclike nucleus carries genetic material in the form of deoxyrib...
Read more