| AR | absolute risk; accounts receivable; achievement ratio; actinic reticuloid [syndrome]; active resista... |
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| ARA | Academy of Rehabilitative Audiometry; acetylene reduction activity; American Rheumatism Association;... |
| ARR | aortic root replacement |
| AWAR | anterior wall of aortic root |
| BOR | basal optic root; before time of operation; bowels open regularly; branchio-oto-renal [syndrome] |
| root avulsion | The tearing away of the anterior and posterior primary nerve roots from the spinal cord, due to severe traction; most often the C5 through T1 roots are affected. (05 Mar 2000) |
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| root cap | <botany> A mass of parenchymtous cells which covers and protects the growing cells at the end of a root; a pileorhiza. The issue found at the apex of roots, overlying the root apical meristem and protecting it from friction as the root grows through the soil. Secretes a glycoprotein mucilage as a lubricant. (18 Nov 1997) |
| root caries | Dental caries involving the tooth root, cementum, or cervical area of the tooth. (12 Dec 1998) |
| root caries index | The ratio of the number of teeth with carious lesions of the root, and/or restorations of the root, to the number of teeth with exposed root surfaces. (05 Mar 2000) |
| root cutting | <botany> Part of a root of a woody plant which, under suitable conditions, takes root and forms a new plant. (09 Oct 1997) |
| root dehiscence | A loss of the buccal or lingual bone overlaying the root portion of a tooth, leaving that area covered by soft tissue only. (05 Mar 2000) |
| root end cyst | An inflammatory odontogenic cyst derived histogenetically from Malassez' epithelial rests surrounding the root apex of a nonvital tooth. Synonym: periapical cyst, radicular cyst, root end cyst. (05 Mar 2000) |
| root end granuloma | Chronic nonsuppurative inflammation of periapical tissue resulting from irritation following pulp disease or endodontic treatment. (12 Dec 1998) |
| root filaments | The small, individual fibre fascicles into which the roots of all of the spinal nerves and several cranial nerves (hypoglossus, vagus, oculomotorius) divide in fanlike fashion before entering or leaving the spinal cord or brainstem; the spinal dorsal root may divide into 8 to 12 such rootlets. Synonym: fila radicularia, root filaments. (05 Mar 2000) |
| root foramen | The opening at the apex of the root of a tooth that gives passage to the nerve and blood vessels. Synonym: foramen apicis dentis, apical dental foramen, root foramen. (05 Mar 2000) |
| root hair cell | <botany> Root epidermal cell, part of which projects from the root surface as a thin tube, thus increasing the root surface area and promoting absorption of water and ions. (18 Nov 1997) |
| root nodule | <plant biology> Globular structure formed on the roots of certain plants, notably legumes and alder, by symbiotic association between the plant and a nitrogen fixing microorganism (Rhizobium in the case of legumes and Frankia in the case of alder and a variety of other plants). (18 Nov 1997) |
| root of facial nerve | <anatomy, nerve> Fibres running from the facial motor nucleus upward to the facial colliculus where they curve around the abducens nucleus and then pass peripherally between the superior olive and sensory nucleus of the trigeminal, to emerge as the facial nerve from the pontomedullary groove. Synonym: radix nervi facialis. (05 Mar 2000) |
| root of foot | Origin: NL, fr. Gr. The flat of the foot, the edge of the eyelid. Cf. 2d Tarse. 1. <anatomy> The ankle; the bones or cartilages of the part of the foot between the metatarsus and the leg, consisting in man of seven short bones. A plate of dense connective tissue or cartilage in the eyelid of man and many animals. Synonym: tarsal cartilage, and tarsal plate. 2. <zoology> The foot of an insect or a crustacean. It usually consists of form two to five joints. Source: Websters Dictionary (01 Mar 1998) |
| root of lung | All the structures entering or leaving the lung at the hilum, forming a pedicle invested with the pleura; includes the bronchi, pulmonary artery and veins, bronchial arteries and veins, lymphatics, and nerves. Synonym: radix pulmonis. (05 Mar 2000) |