Dr. Young's Anatomy Class: Chapter 15 - Special Senses

Introduction

• Focus on special senses: primarily vision and hearing.
• Other senses (taste, smell) involve fewer structures, mainly sensory receptors.

Special Senses Overview

• Olfaction (Smell): Purely chemoreceptors in the nasal cavity.
  • Olfactory nerve (1st cranial nerve) sends signals to the brain.
• Gustation (Taste): Similar to smell, involves taste buds (sensory receptors) on the tongue.
  • Chemical binds to taste bud, sending signals to the brain.
• Vision: Involves multiple structures.
• Audition (Hearing): Significant structures in the ear.
• Vestibular Sensation: Balance/orientation related to hearing structures.

Anatomy of the Eye

• External Structures:

  • Eyelids (palpebrae) and eyelashes: Protect the eye.
  • Conjunctiva: Thin lining covering the eye, associated with conjunctivitis (pinkeye).
  • Lacrimal Apparatus: Tear production and drainage.

• Internal Structures:

  • Six muscles control eye movement, innervated by three cranial nerves (oculomotor, trochlear, abducens).
  • Layers of the Eye:
    • Fibrous layer: Sclera and cornea.
    • Vascular layer: Iris, ciliary body, choroid.
    • Neural layer: Retina (detects light, sends signals via optic nerve).

• Vision Pathway:

  • Complex pathway involving multiple areas of the brain.
  • Visual information crosses at the optic chiasm.

Anatomy of the Ear

• External Ear:

  • Auricle and external auditory canal.
  • Ceruminous glands produce earwax.

• Middle Ear:

  • Tympanic membrane (eardrum).
  • Auditory ossicles: Malleus, incus, stapes.
  • Eustachian tube: Balances pressure, drains fluids.

• Inner Ear:

  • Bony and membranous labyrinth filled with endolymph.
  • Vestibule and Semicircular Canals: Detects head position and movement.
  • Cochlea: Hearing receptors located here, organized in the organ of Corti.

Relevance to Health

• Conditions like conjunctivitis and ear infections can affect the eye and ear.
• Importance of maintaining hearing health (avoiding loud noises to prevent damage to hair cells).

Conclusion

• Understanding the special senses involves recognizing the complex structures and pathways involved in vision and hearing.