| UA | absorption unsharpness; ultra-audible; ultrasonic arteriography; umbilical artery; unauthorized abse... |
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| UE | uncertain etiology; under elbow; uninvolved epidermis; upper esophagus; upper extremity |
| URI | uniform resource identifier; upper respiratory illness; upper respiratory infection |
| US | screen unsharpness ultrasonic, ultrasound; ultrasonography; unconditioned stimulus; unique sequence;... |
| CSN | cardiac sympathetic nerve; carotid sinus nerve |
| upper hybrid waves | <radiobiology> Similar to lower hybrid waves, but at a higher frequency. Not truly propagating waves, but plasma oscillations. (09 Oct 1997) |
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| upper jaw | The upper jaw bone, takes part in the formation of the orbit, hard palate and nasal cavity. (27 Sep 1997) |
| upper jaw bone | The upper jaw bone, takes part in the formation of the orbit, hard palate and nasal cavity. (27 Sep 1997) |
| upper lid | The superior, larger and more mobile of the two eyelids which covers most of the anterior surface of the eyeball, including the cornea, when closed; a portion of the lacrimal gland and the aponeurosis of the levator palpebrae superioris muscle extend into it, the muscle opening the closed eye and providing additional elevation when the gaze is directed upward. Synonym: palpebra superior, upper lid. (05 Mar 2000) |
| upper lip | The muscular fold forming the superior border of the mouth. Synonym: labium superius oris. (05 Mar 2000) |
| 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 respiratory tract | The nasopharynx, oral cavity, and throat. (09 Oct 1997) |
| 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) |
| anacrotic limb | The ascending limb of an arterial pulse tracing. (05 Mar 2000) |