The ear is made of flexible, soft tissue that attaches to the side of the head. It’s divided into three parts called the outer, middle, and inner ear. Each part has an important function in the hearing process.
The outer ear consists of skin and cartilage, called the auricle, or pinna, and the ear canal. The ear drum, or tympanic membrane, is a thin membrane that separates the outer ear from the middle ear.
The middle ear is an air-filled chamber containing three small bones called ossicles. They connect the ear drum to the inner ear and are named the malleus, or hammer, incus, or anvil, and stapes, or stirrup. Normal hearing occurs when the sound waves pass through the ear canal and vibrate the ear drum.
The air chamber in the middle ear connects to the back of the nose via the Eustachian tube. In both ears, the Eustachian tube serves as a pressure-equalizing valve and drains any fluid that collects in the middle ear into the back of the throat.
The final part of the ear is called the inner ear, which includes the cochlea, the vestibule, and semi-circular canals. The cochlea, also known as the organ of hearing, is shaped much like a snail’s shell and has small hair cells called cilia that are bathed in fluid.
Process of Hearing
Pinna collects the sound from the environment and send it to the middle ear in form of vibrations through Tympanic membrane. The Three tiny bones (malleus, incus, and stapes), known as the ossicular chain, act as a bridge and transfer the sound from the eardrum to the oval window, which is the entrance to inner ear. These vibrations are conveyed by the ossicular chain to the oval window.
The inner ear is also called a labyrinth. There are mainly two ducts:
- the outer duct made of bones surrounding walls called Bony labyrinth.
- the inner duct made of membranous material called Membranous labyrinth.
The outer bony labyrinth is further divided into three regions: cochlea, vestibule and semi-circular canals. The scala vestibuli and scala tympani of bony labyrinth contains fluid called perilymph. The scala media of inner membranous labyrinth contains fluid called endolymph.
The perilymph contains large concentration of sodium while the endolymph contains high concentration of potassium.
Vibrations to the oval window causes the perilymph to vibrate.
The organ of corti is a complex arrangement of sensory hair cells. These hair cells are two types
· Outer hair cells
· Inner hair cells
The vibrations are then transmitted to “organ of corti” through perilymph and endolymph.
There are ~ 3500 inner hair cells and 12000 outer hair cells. The mortality of hair cells is important for the normal functioning of cochlea.
The hair cells then transmit the vibration to vestibulo-cochlear nerve which takes signal to brain to complete the process.
For more information contact us – Better Speech & Hearing Clinic, HSR Layout, Bangalore.
Call- 9606404343, betterspeechhearingclinic@gmail.com
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