Understanding Ear Anatomy and Function
The Ear: Balance and Sound Reception
The ear, responsible for balance and receiving acoustic stimuli, is divided into the inner, middle, and external ear.
Ear Structure Overview
The ear comprises the following structures:
- External Ear: pinna, external auditory canal.
- Middle Ear: tympanic cavity, hammer, anvil, stirrup, Eustachian tube.
- Inner Ear: bony labyrinth (vestibule, semicircular canals, cochlea); membranous labyrinth (utricle, saccule).
Detailed Ear Structure
1. External Ear
The external ear receives sound waves and directs them to the middle ear. It includes:
a) Pinna
A cartilaginous expansion that captures sound signals and directs them into the ear canal.
b) External Auditory Canal
A cylindrical canal, approximately 2cm long, containing glands that secrete cerumen (earwax) and hearing villi.
2. Middle Ear
The middle ear consists of:
a) Tympanum (Tympanic Membrane)
A thin, semitransparent membrane that vibrates in response to sound waves.
b) Tympanic Cavity
An air-filled cavity that houses the ossicular chain and acts as a resonance box.
c) Ossicular Chain
Composed of the hammer, anvil, and stirrup, transmitting sound waves to the inner ear.
d) Oval and Round Windows
Flexible structures enabling communication between the middle and inner ear.
3. Inner Ear
Also known as the labyrinth, the inner ear includes:
a) Vestibule
The central portion of the bony labyrinth, containing two sacs. Inflammation can cause labyrinthitis.
b) Semicircular Canals
Responsible for capturing angular accelerations and contributing to balance.
c) Cochlea
A snail-shaped structure containing:
- Ramp-vestibular
- Half-Ramp
- Organ of Corti: The organ of hearing. When sound reaches the cochlea, the membrane upon which the Organ of Corti rests vibrates, deforming cilia and triggering nerve impulses.
Hearing Mechanism
Sound enters the ear, vibrates the eardrum, and is transmitted through the ossicular chain to the stirrup, which connects to the oval window. This initiates the hearing process.