| duffy blood-group system | A blood group consisting mainly of the antigens fy(a) and fy(b), determined by allelic genes, the frequency of which varies profoundly in different races; amorphic genes are common. (12 Dec 1998) |
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| I blood-group system | A blood group related both to the abo and p systems that includes several different antigens found in most people on erythrocytes, in milk, and in saliva. The antibodies react only at low temperatures. (12 Dec 1998) |
| imhoff treatment system | In waste water treatment, a tank without aeration or oxygenation where solids settle out. The solids are digested in a separate compartment in the bottom. (05 Dec 1998) |
| immune system | <immunology> The body system, made up of many organs and cells, that defends the body against infection, disease and foreign substances. The immune system is often stimulated in specific ways to fight cancer cells. (16 Dec 1997) |
| indicator system | In in vitro immunological tests, a combination of reagents used to determine the degree to which immunological reagents have combined (e.g., sensitised erythrocytes in complement-fixation tests; enzyme and substrate in enzyme-linked immunosorbent assays). (05 Mar 2000) |
| information system | Combination of vital and health statistical data from multiple sources, used to derive information and make decisions about the health needs, health resources, costs, use, and outcome of health care. (05 Mar 2000) |
| integumentary system | The skin, hair, and nails; derived from ectoderm and subjacent mesoderm. (05 Mar 2000) |
| intermediary system | One of the lamellae of partially resorbed osteons occurring between newer, complete osteons. Synonym: ground lamella, intermediary system, intermediate lamella. (05 Mar 2000) |
| international system of units | A system of physical units in which the fundamental quantities are length, time, mass, electric current, temperature, luminous intensity, and amount of substance, and the corresponding units are the meter, second, kilogram, ampere, kelvin, candela, and mole. The system has been given official status and recommended for universal use by the general conference on weights and measures. (12 Dec 1998) |
| interofective system | Term applied by W. Cannon to the autonomic nervous system as opposed to the somatic nervous system or exterofective system. (05 Mar 2000) |
| involuntary nervous system | <anatomy> Neurons that are not under conscious control, comprising two antagonistic components, the sympathetic and parasympathetic nervous systems. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: 1. The sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure. 2. The parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. (03 Jul 1999) |
| isolated system | <chemistry> A system which can exchange neither mass nor energy with its surroundings. (09 Jan 1998) |
| occlusal system | The form or design and arrangement of the occlusal and incisal units of a dentition or the teeth on a denture. Synonym: occlusal scheme. (05 Mar 2000) |
| oculomotor system | That part of the central nervous system having to do with eye movements; it is composed of pathways connecting various regions of the cerebrum, brainstem, and ocular nuclei, utilizing multisynaptic articulations. (05 Mar 2000) |
| open system | A system that exchanges energy and materials with the outside environment. (09 Oct 1997) |