| arachnoid of brain | That portion of the arachnoid which lies within the cranial cavity and surrounds the brain and the cranial portion of the subarachnoid space. In several sites it is relatively widely-separated from the pia mater, creating the cranial subarachnoid cisterns. Synonym: arachnoid mater cranialis, arachnoid mater encephali, cerebral part of arachnoid. (05 Mar 2000) |
|---|---|
| arachnoid of spinal cord | That portion of the arachnoid which lies within the vertebral canal and surrounds the spinal cord and the vertebral portion of the subarachnoid space. It extends from the foramen magnum above to the S-2 vertebral level. Since the spinal cord ends at the L-2 vertebral level, a wide separation occurs between the arachnoid and pia mater, the lumbar cistern, filled with cerebrospinal fluid in which the cauda equina is suspended. Synonym: arachnoidea mater spinalis, spinal part of arachnoid. (05 Mar 2000) |
| arachnoid trabecula | Fine, delicate strands composed of fibroblast and extracellular collagen that traverse the subarachnoid space between the arachnoid mater, which is attached to the dura, and the pia mater, which is adherent to the surface of the brain. (05 Mar 2000) |
| arachnoid villi | Tufted prolongations of pia-arachnoid that protrude through the meningeal layer of the dura mater and have a thin limiting membrane; collections of arachnoid villus form arachnoid granulations that lie in venous lacunae at the margin of the superior sagittal sinus; the spongy tissue of the a. Villus contains tubules that serve as one-way valves for transfer of cerebrospinal fluid from the subarachnoid space to the venous system. Both a. Villus and the granulations formed from them are major sites of fluid transfer. See: arachnoid granulations. (05 Mar 2000) |
| arachnoidal | <anatomy> Pertaining to the arachnoid membrane; arachnoid. Source: Websters Dictionary (01 Mar 1998) |
| arachnoidal granulations | Tufted prolongations of pia-arachnoid, composed of numerous arachnoid villi that penetrate dural venous sinuses and effect transfer of cerebrospinal fluid to the venous system. at advanced age these are more numerous and tend to calcify. Synonym: granulationes arachnoideales, arachnoidal granulations, pacchionian bodies, pacchionian corpuscles, pacchionian glands, pacchionian granulations. (05 Mar 2000) |
| arachnoidea | <zoology> Same as Arachnida. Source: Websters Dictionary (01 Mar 1998) |
| arachnoidea mater spinalis | That portion of the arachnoid which lies within the vertebral canal and surrounds the spinal cord and the vertebral portion of the subarachnoid space. It extends from the foramen magnum above to the S-2 vertebral level. Since the spinal cord ends at the L-2 vertebral level, a wide separation occurs between the arachnoid and pia mater, the lumbar cistern, filled with cerebrospinal fluid in which the cauda equina is suspended. Synonym: arachnoidea mater spinalis, spinal part of arachnoid. (05 Mar 2000) |
| arachnoiditis | <pathology> Inflammation of the arachnoid membrane and adjacent subarachnoid space. (27 Sep 1997) |
| arachnological | Of or pertaining to arachnology. Source: Websters Dictionary (01 Mar 1998) |
| arachnologist | One who is versed in, or studies, arachnology. Source: Websters Dictionary (01 Mar 1998) |
| arachnology | <study> The department of zoology which treats of spiders and other Arachnida. Origin: Gr. Spider. (04 Mar 1998) |
| arachnolysin | A haemolytic substance in the venom of certain spiders. (05 Mar 2000) |
| arachnophobia | <psychology> Morbid fear of spiders. Synonym: arachnophobia. Origin: G. Arachne, spider, + phobos, fear (05 Mar 2000) |
| aragonite | <chemical> A mineral identical in composition with calcite or carbonate of lime, but differing from it in its crystalline form and some of its physical characters. Origin: From Aragon, in Spain. Source: Websters Dictionary (01 Mar 1998) |