| life cycle | The entire life history of a living organism. (05 Mar 2000) |
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| life-cycle costing | A method of comparing costs of equipment or buildings based on original costs plus all operating and maintenance costs over the useful life of the equipment. Future costs are discounted. (05 Dec 1998) |
| life cycle stages | The continuous sequence of changes undergone by metamorphosing insects and other animals during the developmental process. (12 Dec 1998) |
| life events | Occurrences in one's daily life, some of which act as stressors. (05 Mar 2000) |
| life expectancy | <epidemiology> Longevity, the average length of life of individuals in a population. (05 Dec 1998) |
| life instinct | The instinct of self-preservation and sexual procreation; the basic urge toward preservation of the species. Synonym: sexual instinct. (05 Mar 2000) |
| life stress | Events or experiences that produce severe strain, e.g., failure on the job, marital separation, loss of a love object. (05 Mar 2000) |
| life support care | Care provided patients requiring extraordinary therapeutic measures in order to sustain and prolong life. (12 Dec 1998) |
| life support systems | Systems that provide all or most of the items necessary for maintaining life and health. Provisions are made for the supplying of oxygen, food, water, temperature and pressure control, disposition of carbon dioxide and body waste. The milieu may be a spacecraft, a submarine, or the surface of the moon. In medical care, usually under hospital conditions, life support care is available. (12 Dec 1998) |
| life table | A representation of the probable years of survivorship of a defined population of subjects; since survivorship is changed by new methods of prevention or treatment, a diachronic study is commonly used because the main interest lies in the composite structure of the current population. (In the summarizing technique used to describe the pattern of mortality and survival in a population, survivors to age x are denoted by the symbol lx and the expectation of life at age x is denoted by the symbol x. (05 Mar 2000) |
| life tables | Summarizing techniques used to describe the pattern of mortality and survival in populations. These methods can be applied to the study not only of death, but also of any defined endpoint such as the onset of disease or the occurrence of disease complications. (12 Dec 1998) |
| alveolar dead space | The difference between physiologic dead space and anatomical dead space; it represents that part of the physiologic dead space resulting from ventilation of relatively underperfused or nonperfused alveoli; it differs specifically in being placed so as to fill and empty in parallel with functional alveoli, rather than being interposed in the conducting tubes between functional alveoli and the external environment. (05 Mar 2000) |
| anatomical dead space | The volume of the conducting airways from the external environment (at the nose and mouth) down to the level at which inspired gas exchanges oxygen and carbon dioxide with pulmonary capillary blood; formerly presumed to extend down to the beginning of alveolar epithelium in the respiratory bronchioles, but more recent evidence indicates that effective gas exchange extends some distance up the thicker-walled conducting airways because of rapid longitudinal mixing. Compare: alveolar dead space, physiologic dead space. Synonym: anatomical airway. (05 Mar 2000) |
| antecubital space | The fossa in front of the elbow, bounded laterally and medially by the humeral origins of the extensors and flexors of the forearm, respectively, and superiorly by an imaginary line connecting the humeral condyles. Synonym: fossa cubitalis, antecubital space, chelidon, triangle of elbow. (05 Mar 2000) |
| anterior clear space | On lateral chest radiographs, the region dorsal to the sternum and ventral to the ascending aorta. Synonym: anterior clear space. (05 Mar 2000) |