| PB | British pharmacopeia [Pharmacopoeia Britannica]; paraffin bath; Paul-Bunnell [antibody]; periodic br... |
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| PBC | peripheral blood cell; point of basal convergence; pre-bed care; primary biliary cirrhosis; progesti... |
| PBF | peripheral blod flow; placental blood flow; pulmonary blood flow |
| PBLC | peripheral blood lymphocyte count; premature birth living child; problem-based learning curriculum |
| PBLT | peripheral blood lymphocyte transformation |
| 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) |
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| 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) |
| 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) |
| O-R system | <abbreviation> Oxidation-reduction system. (05 Mar 2000) |
| oxidation-reduction system | <enzyme> An enzyme system in the tissues by which oxidation and reduction proceed simultaneously through the transference of hydrogen or of one or more electrons from one metabolite to another. See: oxidation-reduction. Synonym: redox system. (05 Mar 2000) |
| thoracolumbar system | See: autonomic nervous system, sympathetic part. (05 Mar 2000) |
| ecological system | <ecology> An ecosystem is the dynamic and interrelating complex of plant and animal communities and their associated non-living environment. The physical and climactic features and all the living and dead organisms in an area that are interrelated in the transfer of energy and material. An interacting complex of a community and its environment functioning as an ecological unit in nature. Differs from system in being a more rigorous definition that encompasses and requires assumptions of energetics, ecological interactions, species adaptations and so forth. (13 Nov 1997) |
| electron optical system | <apparatus> A combination of parts capable of producing and controlling a beam of electrons to produce an image of an object. (05 Aug 1998) |
| electron transport system | The mitochondrial electron transport chain. (18 Nov 1997) |
| endocrine system | The system of glands that release their secretions (hormones) directly into the circulatory system. In addition to the endocrine glands, included are the chromaffin system and the neurosecretory systems. (12 Dec 1998) |
| endomembrane system | <cell biology> Membrane system that ramifies through the cytoplasm. The membranes of the endoplasmic reticulum are separated by 50-200 nm and the cisternal space thus enclosed constitutes a separate compartment. The Golgi region is composed of flattened sacs of membrane that together with endoplasmic reticulum and lysosomes constitute the GERL system. See: smooth endoplasmic reticulum, rough endoplasmic reticulum. (18 Nov 1997) |
| endoscopy, digestive system | Visual examination of the digestive tract by means of a fibreoptic endoscope. It is used to localise, identify, and photograph pathologic alterations, to obtain biopsy material and perform other surgical interventions, and for delivery of medication. (12 Dec 1998) |