Lecture Notes: Anatomy of the Ear

Overview

This lecture covers the anatomy of the ear, including the external, middle, and inner ear, and the function and structure of each component.

Auricle (Pinna): Composed of elastic cartilage allowing flexibility and recoil.
External Acoustic/Auditory Meatus: Canal for sound waves, contains ceruminous glands that produce cerumen to deter insects.
Tympanic Membrane (Eardrum): Connective tissue separating the external ear from the middle ear.

Eustachian Tube: Drains the middle ear into the nasopharynx, helps equalize pressure.
Tensor Tympani Muscle: Skeletal muscle in the middle ear.
Ossicles (Ear Bones):
- Malleus
- Incus
- Stapes: Vibrates against the oval window to transmit sound to the inner ear.
Stapedius Muscle: Connects to the stapes; prevents excessive movement.

Semicircular Canals:
- Bony Labyrinth filled with perilymph
- Semicircular Ducts with endolymph
- Ampulla: Contains crista ampullaris, detects dynamic equilibrium.
Vestibule:
- Contains utricle and saccule with macula for static equilibrium.
- Macula has otoliths (calcium carbonate crystals); related to vertigo.
Cochlea:
- Scala Vestibuli: Upper chamber, perilymph
- Cochlear Duct/Scala Media: Middle chamber, endolymph; contains spiral organ of Corti for sound detection.
- Scala Tympani: Lower chamber, perilymph
Vestibulocochlear Nerve (Cranial Nerve VIII):
- Cochlear Branch: Carries sound information.
- Vestibular Branch: Carries equilibrium information.

Sound Waves: Enter through external acoustic meatus.
Tympanic Membrane: Vibrates, transmitting vibrations to ossicles (malleus, incus, stapes).
Oval Window: Stapes taps on it, creating fluid vibrations in the cochlea.
Scala Vestibuli: Vibrations travel through, bending the basilar membrane.
Spiral Organ of Corti: Hair cells activated, sending signals via cochlear branch to auditory cortex.

Vertigo is caused by dislodged otoliths affecting balance; treated with repositioning or medication.

This lecture detailed the anatomy and physiology of the ear, emphasizing the mechanisms of hearing and balance.