| OP | occipitoparietal; occipitoposterior; occiput posterior; octapeptide; olfactory peduncle; opening pre... |
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| OPLL | ossification of posterior longitudinal ligament |
| PAL | pathology laboratory; peptidyl-alpha-hydroxyglycine alpha-amidating lysine phase alteration plane; p... |
| PAR | participating provider; passive avoidance reaction; perennial allergic rhinitis; photosynthetically ... |
| PAV | percutaneous aortic valvuloplasty; poikiloderma atrophicans vasculare; posterior arch vein; proporti... |
| anterior saemicircular canals | The three bony tubes in the labyrinth of the ear within which the membranous saemicircular ducts are located; they lie in planes at right angles to each other and are known as anterior saemicircular canal, posterior saemicircular canal, and lateral saemicircular canal. Synonym: canales saemicirculares ossei. (05 Mar 2000) |
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| anterior scalene muscle | <anatomy, muscle> Origin, anterior tubercles of transverse processes of third to sixth cervical vertebrae; insertion, scalene tubercle of first rib; action, raises first rib; nerve supply, cervical plexus. Synonym: musculus scalenus anterior, anterior scalene muscle, musculus scalenus anticus. (05 Mar 2000) |
| anterior scleritis | Inflammation of the sclera adjacent to the cornea. (05 Mar 2000) |
| anterior sclerotomy | Incision into the anterior chamber of the eye. (05 Mar 2000) |
| anterior scrotal branch of external pudendal artery | <anatomy, artery> Distribution, skin of anterior scrotum; anastomoses, posterior scrotal branches from internal pudendal artery. Synonym: rami scrotales anteriores arteriae pudendae externae. (05 Mar 2000) |
| anterior scrotal nerves | The branches of the ilioinguinal nerve, distributed to the skin of the root of the penis, mons pubis, adjacent thigh and the anterior surface of the scrotum. Synonym: nervi scrotales anteriores. (05 Mar 2000) |
| anterior scrotal veins | Tributaries of the femoral or exteranl pudendal veins drainign the anterior aspect of the scrotum and the skin and dartos fascia of the shaft and base of the penis. Synonym: venae scrotales anteriores. (05 Mar 2000) |
| anterior segment | A delimited part or section of an organ or other structure which lies in front of or ventral to the other similar parts or sections. 1) segmentum anterius (hepar); the anterior segment of the right lobe of the liver. 2) segmentum anterius (pulmo dexter et sinister); [S 3]; the anterior segment of the superior lobe of the right and left lungs. 3) anterior segment of the eye; the intraocular segment of the eyeball occupied by the aqueous which lies in front of, and is separated from the vitreous-filled posterior segment by, the lens and zonule; it is subdivided by the iris into anterior and posterior chambers. Synonym: segmentum anterius. (05 Mar 2000) |
| anterior serratus muscle | <anatomy, muscle> Origin, from centre of lateral aspect of first eight to nine ribs; insertion, superior and inferior angles and intervening medial margin of scapula; action, rotates scapula and pulls it forward, elevates ribs; nerve supply, long thoracic from brachial plexus. Synonym: musculus serratus anterior, anterior serratus muscle, costoscapularis, musculus serratus magnus. (05 Mar 2000) |
| anterior sinuses | The anterior group of air cells of the ethmoidal sinus's; each sinus communicates with the middle meatus of the nasal cavity. Synonym: sinus ethmoidales anteriores, anterior cells, anterior sinuses, cellulae anteriores. (05 Mar 2000) |
| anterior spinal artery | <anatomy, artery> Origin, intracranial part of vertebral; distribution, spinal cord and pia mater; anastomoses, spinal of intercostal and lumbar arteries. Synonym: arteria spinalis anterior. (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) |
| anterior spinothalamic tract | The more anterior or ventral part of the spinothalamic tract that is involved in tactile sensation. See: spinothalamic tract. Synonym: tractus spinothalamicus anterior, ventral spinothalamic tract. (05 Mar 2000) |
| anterior staphyloma | A bulging near the anterior pole of the eyeball. Synonym: corneal staphyloma. (05 Mar 2000) |
| anterior sternoclavicular ligament | <anatomy> A fibrous band that reinforces the sternoclavicular anteriorly. Synonym: ligamentum sternoclaviculare anterius. (05 Mar 2000) |