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a circular or rounded flat plate; often spelled disc in names of anatomic structures.
articular disk a pad of fibrocartilage or dense fibrous tissue present in some synovial joints.
Bowman's disk one of the flat plates making up a striated muscle fiber.
choked disk papilledema.
ciliary disk pars plana.
embryonic disk (germ disk) (germinal disk) a flattened round bilaminar plate of cells in the blastocyst of a mammal, where the first traces of the embryo are seen; called also embryonic or germinal area.
herniated disk see herniated disk.
intervertebral disk the layer of fibrocartilage between the bodies of adjoining vertebrae; see also herniated disk.
intra-articular d's articular disk.
Merkel's d's small cup-shaped tactile receptors in the skin that are particularly sensitive to continuous pressure.
optic disk the intraocular part of the optic nerve formed by fibers converging from the retina and appearing as a pink to white disk in the retina; there are no sensory receptors in the region and hence no response to stimuli. Called also blind spot.
ruptured disk herniated disk.
slipped disk popular term for herniated disk.
choked diskOphthalmology Papilledema with swelling of the optic nerve head, caused by ↑ intracranial pressure with edema-induced blurring of the disk margins and obliteration of the optic cup, elevation of the nerve head, capillary congestion, hyperemia, venous engorgement, loss of venous pulse, peripapillary exudates, retinal wrinkling, and punctate nerve fiber layer hemorrhage; if pressure is reduced, fundus returns to normal without loss of vision; ↑ intracranial pressure is due to meningoencephalitis, hemorrhage, metabolic disease, toxins, trauma, tumors. See Pseudotumor cerebri.
disk(disk) [Gr. diskos, a dish, quoit]
A flat, round, platelike structure. Synonym: disc
anisotropic diskA band.
The biconcave oval disk of fibrous connective tissue that separates the two joint cavities of the temporomandibular joint on each side.
A thin circular paper (or other substance) used to abrade, cut, or polish teeth or dental appliances.
An oval disk of cells in the blastocyst of a mammal from which the embryo proper develops. Its lower layer, the endoderm, forms the roof of the yolk sac. Its upper layer, the ectoderm, forms the floor of the amniotic cavity. The primitive streak develops on the upper surface of the disk. See: embryo for illus.
[Theodor W. Engelmann, Ger. physiologist, 1843–1909]H band.
A disk of cartilage at the junction of the diaphysis and epiphyses of growing long bones. Cartilage synthesis provides for growth in length; eventually the cartilage is replaced by bone.
A disk of cells on the surface of the yolk of a teloblastic egg from which the embryo develops. Synonym: proligerous disk; blastoderm
Hensen diskSee: Hensen, Christian Andreas Victor.
Rupture of the soft tissue that separates two vertebral bones into the spinal canal or adjacent spinal nerve roots. Herniation of intervertebral disks can cause back pain and, occasionally, loss of neurological function in the distribution of affected nerves. Synonym: herniated intervertebral disk; lumbar disk prolapse; slipped disk See: herniation of nucleus pulposus for illus
herniated intervertebral diskherniated disk.
A modification of the cell membrane of adjacent cardiac muscle cells; it consists of extensive folds and intercellular junctions for electrical and mechanical linkage of contiguous cells.See: illustration
The fibrocartilaginous tissue between the vertebral bodies. The outer portion is the anulus fibrosus; the inner portion is the nucleus pulposus. The disk is a shock absorber, or cushion, and permits movement.
M diskM line.
Merkel diskSee: Merkel disk
The area of the retina where the optic nerve enters.Synonym: blind spot (1)
Placido diskSee: Placido disk
proligerous diskGerminal disk.
Colloquial term for herniated disk.
tactile diskMerkel disk.
A thin, dark disk that transversely bisects the I band (isotropic band) of a striated muscle fiber. The thin filaments, made primarily of actin, are attached to the Z disk; the area between the two Z disks is a sarcomere, the unit of contraction.