Olfactory System

• Olfactory Nerve and Bulb

  • The olfactory nerve is crucial for the sense of smell.

  • The olfactory bulb is located on the interior aspect of the brain.

  • Olfactory nerves extend from the olfactory bulb down through the cribriform plate of the skull.

Components of the Eye

• Eyebrow, Eyelashes, Eyelids

  • Protect the eye and help in preventing debris from entering.

• Conjunctiva

  • The protective tissue covering the eye; can become inflamed (conjunctivitis).

• Lacrimal Gland

  • Located on the superior lateral side of the eye; produces tears.

  • Helps in identifying the side of the eye being viewed due to its position.

• Nasal Lacrimal Duct

  • Drains excess tears, causing a runny nose when eyes are watering.

Anatomy of the Eye

• Optic Nerve (Cranial Nerve II)

  • Carries visual information from the eyeball to the brain, specifically to the posterior part (occipital lobe).

  • Passes through the optic chiasm where some nerve fibers cross to the opposite side.

• Optic Tract

  • Continues from the optic chiasm to the brain, aiding visual processing in the superior colliculi and occipital lobe.

Structure of the Eyeball

• Three Layers of the Eyeball

  1. Outer Fibrous Layer (Fibrous Tunic)

     • Includes the sclera (white part of the eye) and the transparent cornea, which has no blood vessels.

  2. Middle Vascular Layer

     • The choroid supplies blood to the eye; its role is to nourish other eye layers.

  3. Inner Neural Layer

     • The retina, which contains photoreceptor cells responsible for light detection.

Anterior Structures of the Eye

• Iris

  • The colored part of the eye; determines eye color (ex: blue, green, brown).

• Pupil

  • The central hole of the iris that regulates light entry by adjusting its size.

• Lens

  • A clear structure behind the pupil that focuses light on the retina; adjustable thickness aided by the ciliary body and ligaments.

Ciliary Body and Focus Adjustment

• Ciliary Body

  • Smooth muscle responsible for adjusting the lens thickness for proper focus on the retina.

• Process of Light Entry

  • Light passes through the cornea → pupil → lens → focused on the retina.

Retina Features

• Macula and Fovea

  • The macula is responsible for high acuity vision, with fovea as the most sensitive spot within it.

• Optic Disc

  • Location where the optic nerve exits the eye; lacks photosensitive cells, creating a blind spot.

  • Visual information is absent from this area.

Visual Acuity and Identification

• Distinguishing Features

  • Macular and optic disc are easily confused—macula is for sharp vision while the optic disc has no vision capability.

• Optic disc appearance is a key indication during eye examinations; it appears different from the rest of the retina.