| square matrix | A matrix in which the numbers of rows and columns are equal. (05 Mar 2000) |
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| nuclear matrix | <cell biology> Membrane system that surrounds the nucleus of eukaryotic cells. Consists of inner and outer membranes separated by perinuclear space and perforated by nuclear pores. The term should be used in preference to the term nuclear membrane which is potentially very confusing. (18 Nov 1997) |
| identity matrix | A square matrix in which the quantities on the diagnonal from top left to bottom right are all equal to 1 and all the other entries are 0. (05 Mar 2000) |
| territorial matrix | The more intensely basophilic matrix in hyaline cartilage surrounding the lacunae in which the cartilage cells lie. Synonym: territorial matrix. (05 Mar 2000) |
| external matrix | The substance occupying the space between the inner and outer membrane of any organelle (e.g., mitochondria) with a double membrane. (05 Mar 2000) |
| extracellular matrix | Any material produced by cells and secreted into the surrounding medium, but usually applied to the noncellular portion of animal tissues. The ecm of connective tissue is particularly extensive and the properties of the ecm determine the properties of the tissue. In broad terms there are three major components: fibrous elements particularly collagen, elastin or reticulin), link proteins (e.g. Fibronectin, laminin) and space filling molecules (usually glycosaminoglycans). The matrix may be mineralised to resist compression (as in bone) or dominated by tension resisting fibres (as in tendon). The basal lamina of epithelial cells is another commonly encountered ecm. Although ecm is produced by cells, it has recently become clear that the ecm can influence the behaviour of cells quite markedly, an important factor to consider when growing cells in vitro: removing cells from their normal environment can have far reaching effects. (18 Nov 1997) |
| extracellular matrix proteins | Macromolecular organic compounds that contain carbon, hydrogen, oxygen, nitrogen, and usually, sulfur. These macromolecules (proteins) form an intricate meshwork in which cells are embedded to construct tissues. Variations in the relative types of macromolecules and their organization determine the type of extracellular matrix, each adapted to the functional requirements of the tissue. The two main classes of macromolecules that form the extracellular matrix are: glycosaminoglycans, usually linked to proteins (proteoglycans), and fibrous proteins (e.g., collagen, elastin, fibronectins and laminin). (12 Dec 1998) |