Lecture Notes: Structure of the Inner Ear

Overview

• The lecture introduces the structure of the inner ear.
• Each component of the inner ear will be discussed in detail in separate videos.

Anatomy of the Inner Ear

Cochlea

• Structure: Snail-like appearance; consists of three chambers:
  • Scala Vestibuli: Upper chamber; associated with the oval window tapped by the stapes, filled with perilymph.
  • Scala Media (Cochlear Duct): Middle chamber; filled with potassium-rich endolymph, part of the inner membranous labyrinth.
  • Scala Tympani: Lower chamber; ends at the round window, filled with perilymph.
• Helicotrema: Point where scala vestibuli and scala tympani meet and perilymph mixes.
• Important Receptors: Consists of hair cells covered with tectorial membrane forming the spiral organ of Corti for sound detection.

Vestibule

• Structure: Outer bony labyrinth filled with perilymph.
• Components:
  • Utricle and Saccule: Filled with endolymph, part of inner membranous labyrinth, contain maculae for static equilibrium.
  • Maculae: Detect linear acceleration and head tilts; consist of hair cells and otolithic membranes with otoconia.

Semicircular Canals

• Structure: Three canals filled with perilymph (outer bony labyrinth):
  • Anterior Semicircular Canal
  • Posterior Semicircular Canal
  • Lateral Semicircular Canal
• Ampulla: Dilated regions housing cristae ampullares, important for dynamic equilibrium (angular acceleration).

Nerve Connections

• Cochlear Branch: Part of the vestibulocochlear nerve (cranial nerve 8), originates from the cochlea.
• Vestibular Branch: Part of the vestibulocochlear nerve, originates from vestibule and semicircular canals.
• Ganglia:
  • Spiral Ganglion: Related to the cochlear branch.
  • Scarpa's Ganglion: Related to the vestibular branch, containing pseudo-unipolar cell bodies.

Functions of Inner Ear Components

• Cochlea: Sound wave detection and conversion into electrical signals via the spiral organ of Corti.
• Vestibule (Utricle and Saccule): Detect static equilibrium and linear acceleration.
• Semicircular Canals: Detect dynamic equilibrium, head rotations, and angular acceleration.

Additional Information

• Further videos will cover detailed anatomy and physiology of the vestibule, semicircular canals, and cochlea.
• The lecture also mentions additional resources for studying ear anatomy, including external and middle ear structures.

Conclusion

• Encouragement for viewers to engage with the content and subscribe for more educational materials.