| intermediolateral cell column of spinal cord | The cell column that forms the lateral horn of the spinal cord's gray matter. Extending from the first thoracic through the second lumbar segment, the column contains the autonomic motor neurons that give rise to the preganglionic fibres of the sympathetic system. Synonym: intermediolateral cell column of spinal cord, nucleus intermediolateralis. (05 Mar 2000) |
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| thoracic part of spinal cord | The part of the spinal cord which consists of the twelve thoracic segments of the spinal cord from which the twelve pairs of thoracic nerves originate. Synonym: pars thoracica medullae spinalis, segmenta medullae spinalis thoracica. (05 Mar 2000) |
| lateral column of spinal cord | A slight protrusion of the gray matter of the spinal cord into the lateral funiculus of either side, especially marked in the thoracic region where it encloses preganglionic motor neurons of the sympathetic division of the autonomic nervous system; it corresponds to the lateral horn appearing in transverse sections of the spinal cord. See: gray columns. Synonym: columna lateralis, lateral column of spinal cord. (05 Mar 2000) |
| lateral funiculus of spinal cord | The lateral white column of the spinal cord between the lines of exit and entrance of the anterior and posterior nerve roots. Synonym: funiculus lateralis, anterolateral column of spinal cord, lateral funiculus of spinal cord. (05 Mar 2000) |
| lumbar enlargement of spinal cord | A spindle-shaped swelling of the spinal cord beginning at the level of the tenth thoracic vertebra and tapering into the medullary cone, with maximum thickness opposite the last thoracic vertebra, consequential to the innervation of the lower limb. Synonym: intumescentia lumbalis, lumbar enlargement of spinal cord. (05 Mar 2000) |
| lumbar part of spinal cord | Portion of spinal cord which consists of the five lumbar segments (L1-L5) and from which five pairs of lumbar spinal nerves originate; in the adult it is located in the T10-L1 portion of the vertebral canal, and is enlarged relative to other parts of the cord due to its involvement in innervation of the lower limb. (05 Mar 2000) |
| lumbar segments of spinal cord | The five lumbar segments of the spinal cord which give rise to the five pairs of lumbar spinal nerves and constitute the lumbar part of the spinal cord. Synonym: segmenta medullae spinalis lumbaria. (05 Mar 2000) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| reaction formation | In psychoanalysis, a postulated defense mechanism in which attitudes and behaviours that are adopted are the opposites of that which the individual would ordinarily be expected to express and actually feel at an unconscious level. (05 Mar 2000) |
| pattern formation | <cell biology> One of the classic problems in developmental biology is the way in which complex patterns are formed from an apparently uniform field of cells. Various hypotheses have been put forward and there is now evidence for the existence of gradients of diffusible substances (morphogens) specifying the differentiative pathway that should be followed according to the concentration of the morphogen around the cell. (18 Nov 1997) |
| personality formation | The life history associated with the development of individual patterns and of one's individuality. (05 Mar 2000) |
| rosette formation | The in vitro formation of clusters consisting of a cell (usually a lymphocyte) surrounded by antigenic cells or antigen-bearing particles (usually erythrocytes, which may or may not be coated with antibody or antibody and complement). The rosette-forming cell may be an antibody-forming cell, a memory cell, a T-cell, a cell bearing surface cytophilic antibodies, or a monocyte possessing fc receptors. Rosette formation can be used to identify specific populations of these cells. (12 Dec 1998) |
| rouleaux formation | The arrangement of red blood cells in fluid blood (or in diluted suspensions) with their biconcave surfaces in apposition, thereby forming groups that resemble stacks of coins. Synonym: false agglutination, pseudoagglutination. Origin: Fr. Pl. Of rouleau, a roll (05 Mar 2000) |
| concept formation | A cognitive process involving the formation of ideas generalised from the knowledge of qualities, aspects, and relations of objects. (12 Dec 1998) |
| heat of formation | The heat (expressed in calories or joules) absorbed or liberated during the (hypothetical) reaction in which a mole of a compound is formed from the necessary elements, in elemental form. (05 Mar 2000) |