| upper lip | The muscular fold forming the superior border of the mouth. Synonym: labium superius oris. (05 Mar 2000) |
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| upper lobe of lung | The lobe of the right lung that lies above the oblique and horizontal fissures and includes the apical, posterior and anterior bronchopulmonary segments; in the left lung, the lobe lies above the oblique fissure and contains the apicoposterior, anterior, superior lingular and inferior lingular segments. Synonym: lobus superior pulmonis, upper lobe of lung. (05 Mar 2000) |
| upper/lower lobe predominance | <radiology> Upper lobe, usually site of greatest disease due to poorer clearance, bronchogenic carcinoma, pneumoconioses, histiocytosis X, sarcoidosis, ankylosing spondylitis, lower lobe, scleroderma (12 Dec 1998) |
| upper motor neuron | Clinical term indicating those neuron's of the motor cortex that contribute to the formation of the pyramidal or corticospinal and corticobulbar tracts, as distinguished from the lower motor neuron's innervating the skeletal muscles. Although not motor neuron's in the strict sense, these cortical neuron's became colloquially classified as motor neuron's because their stimulation produces movement and their destruction causes severe disorders of movement. See: motor neuron, motor cortex. (05 Mar 2000) |
| upper motor neuron lesion | Injury to cerebral descending (corticonuclear) fibres above the brainstem or spinal motor nerve nucleus. Synonym: upper motor neuron lesion. (05 Mar 2000) |
| upper nodal extrasystole | An obsolete term for a nodal extrasystole supposed to arise from the upper part of the A-V node; recognised in the electrocardiogram by a retrograde P wave preceding the QRS complex by an abnormally short P-R interval. (05 Mar 2000) |
| upper respiratory infection | Any number of viral or bacterial infections that includes infections of the throat, nasopharynx, sinuses, larynx, trachea or bronchi. (27 Sep 1997) |
| upper subscapular nerve | Two branches of the posterior cord of the brachial plexus, an upper and lower, supplying the subscapularis muscle; the lower subscapular nerve also supplies the teres major muscle. Synonym: nervi subscapulares. (05 Mar 2000) |
| upper thoracic splanchnic nerves | Part of the cardiopulmonary splanchnic nerves from the second to fifth segments of the thoracic sympathetic trunk that pass medially and anteriorly to enter the cardiac plexus; they convey postsynaptic sympathetic fibres to, and visceral afferent (pain) fibres from, the heart. Synonym: nervi cardiaci thoracici, upper thoracic splanchnic nerves. (05 Mar 2000) |
| upper uterine segment | The main portion of the body of the gravid uterus, the contraction of which furnishes the chief force of expulsion in labour. (05 Mar 2000) |
| alimentary tract | The passage leading from the mouth to the anus through the pharynx, oesophagus, stomach, and intestine. Synonym: alimentary canal, alimentary tract, digestive tube, tubus digestorius. (05 Mar 2000) |
| alimentary tract smear | A group of cytologic specimens containing material from the mouth (oral smear), oesophagus and stomach (gastric smear), duodenum (paraduodenal smear), and colon, obtained by specialised lavage techniques; used principally for the diagnosis of cancer of those areas. (05 Mar 2000) |
| anterior corticospinal tract | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| anterior pyramidal tract | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| anterior spinocerebellar tract | A bundle of fibres originating in the base of the posterior horn and zona intermedia throughout lumbosacral segments of the spinal cord, crossing to the opposite side and ascending in a peripheral position in the ventral half of the lateral funiculus. In its ascent through the rhombencephalon, the tract curves sharply dorsalward along the rostral border of the trigeminal motor nucleus, entering the cerebellum in a caudal direction over the dorsal surface of the superior cerebellar peduncle, and terminating as mossy fibres in the granular layer of the cortex of the cerebellar vermis. The bundle conveys proprioceptive and exteroceptive information largely from the opposite lower extremity. Synonym: tractus spinocerebellaris anterior, Gowers' column, Gowers' tract, ventral spinocerebellar tract. (05 Mar 2000) |