Functions of the ear
- Maintaining body balance and posture
Adaptations of the ear to its Functions
The ear is divided into:
- Outer ear
Pinna is funnel shaped to direct sound waves into auditory canal;its large to offer large surface area for collection of sound waves;
2. Auditory meatus/canal
Tube that directs sound waves to ear drum.
Lined with hairs to trap solid particles.
Lined with wax secreting cells to trap dust.
Wax also maintains flexibility of the eardrum.
2. Middle ear. Its air filled
- Tympanic membrane/ear drum.
It’s a thin tough membrane.
It transforms sound waves into vibrations.
They are three bones; malleus, incus and stapes.
They receive vibrations from tympanic membrane and amplify them then transmit them to the oval window.
3. Eustachian tube
Connects middle ear and pharynx.
Equalizes pressure between the middle ear and outer ear preventing distortion of the ear drum.
- Oval window
- Picks vibrations from the ossicles and transmit them to inner ear.
- Round window
- Bring back vibrations from the inner into the middle ear.
3. Inner ear. Its fluid filled
It’s responsible for hearing
It’s filled with endolymph and perilymph
Highly coiled to occupy a small space ; and increase surface area ; for accommodation of many sensory cells
Vibrations from oval window are transmitted to perilymph which vibrates
Sensory cells are stimulated by these vibrations to generate nerve impulses which are transmitted to the brain for interpretation.
2. Semi circular canals
Has semi circular canals which are at right angles to each other
Each canal has a swelling called ampulla at one end containing sensory cells.
Movement of endolymph in canal helps to detect changes in position of the body and maintain body balance posture in relation to head movement.
Has utriculus and sacculus that have sensory cells.
It maintains body balance posture in relation to gravity.
NB/ Auditory nerve – transmits nerve impulses to the brain for interpretations.
Deffects of the Ear