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

How HIV Causes Infections

-
HIV transmission occurs when a person is exposed to body fluids infected with the virus, such as blood, semen, vaginal secretions, and breast milk. The primary modes of HIV transmission are (1) sexual relations with an infected person (see Sexually Transmitted Infections ); (2) sharing hypodermic needles or accidental pricking by a needle contaminated with infected blood; and (3) transfer of the virus from an infected mother to her baby during pregnancy, childbirth, or through breast-feeding. When HIV enters the body, it infects lymphocytes, which are a type of white blood cell in the immune system . HIV uses its glycoproteins to attach itself to receptors on the surface of a lymphocyte. The outer envelope of HIV then fuses with the lymphocyte, enabling the HIV capsid to enter the lymphocyte itself. HIV commandeers the genetic material of the lymphocyte, instructing the cell to replicate more viruses. The newly formed viruses break free from the host, destroying the cell in the process
Read more

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