| lens, simple | <microscopy> A glass disk ground and polished with a spherical figure on one side and a plano, concave, or convex configuration on the other side. (05 Aug 1998) |
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| lens stars | Congenital cataracts with opacities along the suture lines of the lens; may be anterior or posterior or both. (05 Mar 2000) |
| lens subluxation | Incomplete rupture of the zonule with the displaced lens remaining behind the pupil. In dislocation, or complete rupture, the lens is displaced forward into the anterior chamber or backward into the vitreous body. When congenital, this condition is known as ectopia lentis. (12 Dec 1998) |
| lens sutures | 9 to 12 faint lines on the anterior and posterior surfaces of the lens that radiate from the poles toward the equator; they mark the lines along which the ends of lens fibres abut. Synonym: lens stars, lens sutures. (05 Mar 2000) |
| lens vesicle | In the embryo, the ectodermal invagination that forms opposite the optic cup; it is the primordium of the lens of the eye. Synonym: lenticular vesicle. (05 Mar 2000) |
| lighthouse lens | <physics> A lens built up, progressively, in zones or steps, each zone with its own individual radius. Considerable spherical correction is attained, and the weight of the lens is greatly reduced. Fresnel lenses were originally designed for lighthouses but they are now attainable for small spotlights, automobile headlights, and similar uses. (05 Aug 1998) |
| apex of the posterior horn | The pointed extremity of each posterior gray column or cornu of the spinal cord. Synonym: apex cornus posterioris, caput cornus, tip of posterior horn. (05 Mar 2000) |
| arcus posterior atlantis | The posterior arch of the atlas that connects the lateral masses of the atlas posteriorly, forming the posterior wall of the vertebral canal at this level. Synonym: arcus posterior atlantis. (05 Mar 2000) |
| area intercondylaris posterior tibiae | The deep notch between the tibial condyles posteriorly to which attaches the posterior cruciate ligament. Synonym: area intercondylaris posterior tibiae. (05 Mar 2000) |
| arteria alveolaris superior posterior | <anatomy, artery> Origin, 3rd part of maxillary artery within pterygopalatine fossa; distribution, molar and premolar teeth, gingiva and mucous membrane of maxillary sinus. Synonym: arteria alveolaris superior posterior, posterior alveolar artery, posterior dental artery. (05 Mar 2000) |
| arteria auricularis posterior | <anatomy, artery> Origin: posterior aspect of external carotid just above the digastric muscle; course: ascends first between parotid gland and styloid process then between cartilage of auricle and the mastoid process; branches: muscular (digastric, stylohyoid and sternocleidomastoid), glandular (parotid), stylomastoid artery, occipital and auricular; anastomoses: anterior tympanic artery (via the stylomastoid artery) and occipital artery. Synonym: arteria auricularis posterior. (05 Mar 2000) |
| arteria caecalis posterior | <anatomy, artery> Origin, ileocolic artery; distribution, posterior region of caecum. Synonym: arteria caecalis posterior. (05 Mar 2000) |
| arteria cerebelli inferior posterior | <anatomy, artery> Origin, vertebral; distribution, lateral medulla, choroid plexus of fourth ventricle, and cerebellum; anastomoses, superior cerebellar and anterior inferior cerebellar. Synonym: arteria cerebelli inferior posterior. (05 Mar 2000) |
| arteria cerebri posterior | <anatomy, artery> Formed by the bifurcation of the basilar artery; it passes around the cerebral peduncle to reach the medial aspect of the hemisphere; for descriptive purposes it is divided into three parts: 1) the precommunical part (P1 segment of clinical terminology), the part before the junction with the posterior communicating artery, supplying parts of the thalamus, hypothalamus, and midbrain; 2) the postcommunical part (P2), supplying the thalamus, cerebral peduncles, and the choroid plexuses of the lateral and third ventricles; and 3) the terminal or cortical part, supplying the cortex of the temporal (P3) and occipital (P4) lobes. Synonym: arteria cerebri posterior. (05 Mar 2000) |
| arteria choroidea posterior | <anatomy, artery> One of several choroid branches of the P2 segment of the posterior cerebral artery that supply the choroid plexus of the body of the lateral ventricle and of the third ventricle. Synonym: arteria choroidea posterior. (05 Mar 2000) |