| secondary interatrial foramen | A secondary opening appearing in the upper part of the septum primum in the sixth week of embryonic life, just prior to the closure of the interatrial foramen primum. Synonym: ostium secundum, secondary interatrial foramen. (05 Mar 2000) |
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| secondary leukaemia | A leukaemia arising from either previous chemotherapy or radiotherapy or as the development of a pre-existing condition, such as myelodysplasia. Origin: Gr. Haima = blood (13 Nov 1997) |
| secondary lung cancer | The spread of cancerous tumours from a distant organ to the lung. Due to the lungs tremendous blood and lymphatic supply it is a frequent site for metastatic cancer. Cancers which commonly metastasize to the lung include osteosarcoma, breast cancer, neuroblastoma, Wilm's tumour and non-Hodgkin's lymphomas. (27 Sep 1997) |
| secondary lymphoid tissue | <anatomy> Tissue that is particularly rich in lymphocytes (and accessory cells such as macrophages and reticular cells), particularly the lymph nodes, spleen, thymus, Peyer's patches, pharyngeal tonsils, adenoids and (in birds) the Bursa of Fabricius. Central lymphoid tissue: A term occasionally used as synonym for primary lymphoid tissue but should be avoided to prevent confusion between anatomical location, which is irrelevant and centrality in the system. Peripheral lymphoid tissue: Secondary lymphoid tissue, not necessarily located peripherally. Primary lymphoid tissue: Lymphoid tissues in which immune cells develop as opposed to the secondary or peripheral lymphoid tissues in which antigen independent or antigen dependent stages of maturation take place and in which responsive lymphocytes are found. Primary lymphoid tissues are foetal liver, adult bone marrow and thymus (and Bursa of Fabricius in birds). Secondary tissues are lymph nodes, spleen, tonsils and mucosa associated lymphoid tissue. (20 Mar 1998) |
| secondary lysosome | <cell biology> Term used to describe intracellular vacuoles formed by the fusion of lysosomes with organelles (autosomes) or with primary phagosomes. Residual bodies are the remnants of secondary lysosomes containing indigestible material. Origin: Gr. Soma = body (18 Nov 1997) |
| secondary lysosomes | Lysosome's in which lysis takes place, owing to the activity of hydrolytic enzymes; they are believed to eventually become residual bodies. Synonym: definitive lysosomes, digestive vacuole. (05 Mar 2000) |
| secondary medical care | Medical care by a physician who acts as a consultant at the request of the primary physician. (05 Mar 2000) |
| secondary megaureter | Hydroureter secondary to vesicoureteral reflux or distal obstruction. (05 Mar 2000) |
| secondary mesoderm | Mesoderm derived from the primitive streak and lying between the ectoderm and endoderm. Synonym: secondary mesoderm. (05 Mar 2000) |
| secondary metabolism | Pathways producing specialised metabolic products that are not found inevery cell. (09 Oct 1997) |
| secondary metabolite | <biochemistry> Chemicals that are usually unique to one organism or class of organisms, and are not essential to cell survival. They perform specialised functions, for example, degrading food sources or fighting off other organisms. Many of the chemicals that plants or microorganisms produce that are of biochemical interest are secondary metabolites, including antibiotics. (14 Nov 1997) |
| secondary methemoglobinaemia | Methemoglobinaemia caused by various chemical agents, such as nitrites. Synonym: enterogenous methemoglobinaemia, secondary methemoglobinaemia. (05 Mar 2000) |
| secondary myeloid metaplasia | Myeloid metaplasia occurring in individuals with another disease. Synonym: symptomatic myeloid metaplasia. (05 Mar 2000) |
| secondary narcissism | In psychoanalysis, the psychic energy once attached to external objects, but now withdrawn from those objects and reinvested in the ego. (05 Mar 2000) |
| secondary nodule | A lymphatic nodule having a germinal centre. (05 Mar 2000) |