| ORD | optical rotatory dispersion; oral radiation death |
|---|---|
| OROS | oral osmotic |
| ORT | object relations technique; operating room technician; oral rehydration therapy |
| OS | left eye [Lat. oculus sinister]; occipitosacral; occupational safety; office surgery; Omenn syndrome... |
| OSCC | oral squamous cell carcinoma |
| primary neuronal degeneration | <disease> A progressive, neurodegenerative disease characterised by loss of function and death of nerve cells in several areas of the brain leading to loss of cognitive function such as memory and language. The cause of nerve cell death is unknown but the cells are recognised by the appearance of unusual helical protein filaments in the nerve cells (neurofibrillary tangles) and by degeneration in cortical regions of brain, especially frontal and temporal lobes. Alzheimer's disease is the most common cause of dementia. (22 May 1997) |
|---|---|
| primary nodule | A lymphatic nodule having small lymphocytes and lacking a germinal centre. (05 Mar 2000) |
| primary nondisjunction | Nondisjunction occurring in a previously normal cell. (05 Mar 2000) |
| primary nursing care | The primary responsibility of one nurse for the planning, evaluation, and care of a patient throughout the course of illness, convalescence, and recovery. (12 Dec 1998) |
| primary oocyte | <cell biology, gynaecology> The enlarging ovum before maturity is reached, as opposed to the secondary oocyte or polar body. (18 Nov 1997) |
| primary organiser | The organiser situated on the dorsal lip of the blastopore. (05 Mar 2000) |
| primary ovarian follicle | An ovarian follicle before the appearance of an antrum; marked by developmental changes in the oocyte and follicular cells so that the latter form one or more layers of cuboidal or columnar cells; the follicle becomes surrounded by a sheath of stroma, the theca. Synonym: folliculus ovaricus primarius. (05 Mar 2000) |
| primary palate | In the early embryo, the mesoderm-filled shelf, formed from the medial nasal process, that anteriorly separates the oral cavity below from the primitive nasal cavities above. Synonym: primitive palate. (05 Mar 2000) |
| primary pentosuria | essential pentosuria |
| primary pigmentary degeneration of retina | A hereditary disorder of the retina mainly affecting photoreceptors and retinal pigment epithelium; a miscellaneous category including Friedreich's ataxia, Refsum's disease, and abetalipoproteinaemia. Synonym: primary pigmentary degeneration of retina. (05 Mar 2000) |
| primary point of ossification | This is the first site where bone begins to form in the shaft of a long bone or in the body of an irregular bone. Synonym: punctum ossificationis primarium, primary point of ossification. (05 Mar 2000) |
| primary prevention | Prevention of disease or mental disorders in susceptible individuals or populations through promotion of health, including mental health, and specific protection, as in immunization, as distinguished from the prevention of complications or after-effects of existing disease. (12 Dec 1998) |
| primary process | In psychoanalysis, the mental process directly related to the functions of the primitive life forces associated with the id and characteristic of unconscious mental activity; marked by unorganised, illogical thinking and by the tendency to seek immediate discharge and gratification of instinctual demands. Compare: secondary process. (05 Mar 2000) |
| primary producer | An organism that uses light to synthesise new organic material from carbon dioxide. (09 Oct 1997) |
| primary production | Production of organic substances by photosynthesis, the quantity of material so produced per unit time. (09 Oct 1997) |