optic canal

Examples of optic canal in the following topics:

• Orbits

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

• Optic (II) Nerve

  • The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
  • The optic nerve is also known as cranial nerve II.
  • Each human optic nerve contains between 770,000 and 1.7 million nerve fibers.
  • 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 postero-medially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.

• Foramina

  • Optic foramen: Located in the sphenoid, it allows the passage of the ophthalmic artery and nerve from the optic canal into the orbit.

• 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 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.

• Brain Tumors

  • A brain tumor is an intracranial solid neoplasm—a tumor (defined as an abnormal growth of cells)—within the brain or the central spinal canal.
  • Brain tumors include all tumors inside the cranium or in the central spinal canal.
  • 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).

• Embryonic Development of the Brain

  • The hollow interior is called the neural canal.
  • The optical vesicle (which will eventually become the optic nerve, retina and iris) forms at the basal plate of the prosencephalon.

• Supply of Blood and Nerves to Bone

  • Blood is supplied to mature compact bone through the Haversian canal, formed when individual lamellae form concentric rings around larger longitudinal canals (approx. 50 µm in diameter) within the bone tissue.
  • The canals and the surrounding lamellae (8-15) are called a Haversian system or an osteon.
  • A Haversian canal generally contains one or two capillaries and nerve fibers.
  • Volkmann's canals are channels that assist with blood and nerve supply from the periosteum to the Haversian canal.
  • The Haversian canals surround blood vessels and nerve cells throughout the bone.

• Impacted Cerumen

  • Earwax, or cerumen, is a yellowish waxy substance secreted in the ear canal which can affect hearing if produced excessively.
  • Earwax, also known by the medical term cerumen, is a yellowish waxy substance secreted in the ear canal of humans and other mammals.
  • Excessive earwax may impede the passage of sound in the ear canal, causing conductive hearing loss.
  • Cerumen is produced in the outer third of the cartilaginous portion of the human ear canal.
  • A curette method is more likely to be used by otolaryngologists when the ear canal is partially occluded and the material is not adhering to the skin of the ear canal.

• Root Canal Therapy

  • This set of procedures is commonly referred to as a "root canal" .
  • This procedure is known as root canal therapy.
  • The alternatives to root canal therapy include no treatment, tooth extraction, or the 3Mix-MP procedure.
  • Recent studies indicate that substances commonly used to clean the root canal space incompletely sterilize the canal.
  • However, a properly restored tooth following root canal therapy yields long-term success rates near 97%.

• Embryonic Development

  • The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube, the neural tube or neural canal, the ectodermal wall of which forms the rudiment of the nervous system.
  • The prosencephalon further goes on to develop into the telencephalon (the forebrain or cerebrum) and the diencephalon (the optic vesicles and hypothalamus).