| secondary wall | <plant biology> The part of the plant cell wall which is laid down on top of the primary wall after the wall has ceased to increase in surface area. Only occurs in certain cell types, for example tracheids, vessel elements and sclerenchyma. Differs from the primary wall both in composition and structure and is often diagnostic for a particular cell type. (18 Nov 1997) |
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| secondary X zone | An adrenocortical zone, situated in the inner zona fasciculata, that appears upon postpubertal gonadectomy in some male rodents, most notably the mouse; the development of this zone is believed to be stimulated by pituitary gonadotropins. (05 Mar 2000) |
| spectrometry, mass, secondary ion | A mass-spectrometric technique that is used for microscopic chemical analysis. A beam of primary ions with an energy of 5-20 kiloelectronvolts (kev) bombards a small spot on the surface of the sample under ultra-high vacuum conditions. Positive and negative secondary ions sputtered from the surface are analyzed in a mass spectrometer in regards to their mass-to-charge ratio. (12 Dec 1998) |
| dentin, secondary | Dentin formed and deposited in response to a normal or slightly abnormal stimulus, after the complete formation of the tooth. (12 Dec 1998) |
| osteoarthropathy, secondary hypertrophic | Symmetrical osteitis of the four limbs, chiefly localised to the phalanges and the terminal epiphyses of the long bones of the forearm and leg, sometimes extending to the proximal ends of the limbs and the flat bones, and accompanied by dorsal kyphosis and joint involvement. It is often secondary to chronic conditions of the lungs and heart. (12 Dec 1998) |