optic disc

Examples of optic disc in the following topics:

• Brain Tumors

  • Consequences of intracranial hypertension: Large tumors or tumors with extensive perifocal swelling (edema) inevitably lead to elevated intracranial pressure (intracranial hypertension), which translates clinically into headaches, vomiting (sometimes without nausea), altered state of consciousness (somnolence, coma), dilation of the pupil on the side of the lesion (anisocoria), papilledema (prominent optic disc at the funduscopic eye examination).

• Bilaminar Embryonic Disc Development

  • The floor of the amniotic cavity is formed by the embryonic disc.
  • The embryonic disc is derived from the epiblast layer, which lies between the hypoblast layer and the amnion.
  • The embryonic disc forms during early development.
  • The formation of the bilaminar embryonic disc precedes gastrulation.
  • As gastrulation progresses, the embryonic disc becomes trilaminar and the notochord is formed.

• Herniated (Slipped) Disc

  • A disc herniation is a common injury caused by a tear in the fibrous ring of an intervertebral disc, allowing the central portion to bulge.
  • A spinal disc herniation is a medical condition affecting the spine in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion to bulge out beyond the damaged outer rings .
  • The condition is widely referred to as a slipped disc, but this term is not medically accurate as the spinal discs are fixed in position between the vertebrae and cannot in fact "slip. " A herniated disc may occur due to trauma, lifting injuries, or other factors.
  • If the herniated disc is in the lumbar region (where the majority of herniated discs occur), the patient may also experience sciatica due to irritation of one of the nerve roots of the sciatic nerve.
  • In the majority of cases, spinal disc herniation doesn't require surgery.

• Optic (II) Nerve

  • The optic nerve is also known as cranial nerve II.
  • The optic nerve is the second of twelve paired cranial nerves.
  • As a consequence, optic nerve damage produces irreversible blindness.
  • The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running posteromedially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.
  • An illustration of the brain highlighting the optic nerve and optic tract.

• Development of Vision

  • Development of the optic vesicles starts in the three-week embryo from a progressively deepening groove in the neural plate called the optic sulcus.
  • As this expands, the rostral neuropore (the exit of the brain cavity out of the embryo) closes and the optic sulcus and the neural plate becomes the optic vesicle.
  • The lens then acts as an inducer back to the optic vesicle to transform it into the optic cup and back to the epidermis to transform it into the cornea.
  • Iris is formed from the optic cup cells.
  • After the closure of the tube they are known as the optic vesicles.

• Cartilaginous Joints: Symphyses

  • Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine.
  • The discs consist of an outer annulus fibrosus that surrounds the inner nucleus pulposus.
  • The annulus fibrosus and the nucleus pulposus distribute pressure evenly across the disc.
  • When one develops a prolapsed disc, the jelly (the nucleus pulposus) is forced out of the doughnut (the disc) and may put pressure on the nerve located near the disc, potentially causing symptoms of sciatica.
  • Aging causes disc degeneration, in which the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, limiting the ability of the disc to absorb shock.

• Microscopic Anatomy

  • Actin molecules are bound to the Z-disc, which forms the borders of the sarcomere.
  • Intercalated discs are gap junctions that link cardiomyocytes so that electrical impulses (action potentials) can travel between cells.
  • In cardiac muscle, intercalated discs connecting cardiomyocytes to the syncytium, a multinucleated muscle cell, to support the rapid spread of action potentials and the synchronized contraction of the myocardium.
  • Intercalated discs consist of three types of cell-cell junctions, most of which are found in other tissues besides cardiac muscle:
  • Under light microscopy, intercalated discs appear as thin lines dividing adjacent cardiac muscle cells and running perpendicular to the direction of muscle fibers.

• Orbits

  • To the rear of the orbit, the optic foramen opens into the optical canal through which the optic nerve and ophthalmic artery pass.
  • Finally, the sphenoid bone forms the posterior wall of the orbit and also contributes to the formation of the optic canal.

• Sciatic Nerve Injury

  • Sciatica is also referred to as lumbar radiculopathy, which involves compression of the sciatic nerve roots caused by a herniated (torn) or protruding disc in the lower back.
  • This can occur as a result of a spinal disk bulge or a spinal disc herniation (a herniated intervertebral disc), or from roughening, enlarging, or misalignment (spondylolisthesis) of the vertebrae, or as a result of degenerated discs that can reduce the diameter of the lateral foramen (natural hole) through which nerve roots exit the spine.
  • The intervertebral discs consist of an annulus fibrosus, which forms a ring surrounding the inner nucleus pulposus.

• Paralysis

  • Their intervertebral disc material can calcify and become more brittle.
  • In such cases, the disc may rupture, with disc material ending up in the spinal canal, or rupturing more laterally to press on spinal nerves.
  • If no signs of pain can be elicited, surgery should be performed within 24 hours of the incident, to remove the disc material and relieve pressure on the spinal cord.
  • This is a microscopic piece of disc material that breaks off and becomes lodged in a spinal artery.