There are two part to your dog’s external ear. The pinna and the external ear canal. The pinna, or the ear flap, gives each breed of dog its distinctive look. The ear flap is made up of cartilage which gives the ear strength. The coned shape structure of the ear delivers sound to the external ear canal. The external ear canal also called the auditory canal picks up the sound and sends it down the canal to the ear drum. This canal runs down the side of the head diagonally and then horizontally into the head.
The middle ear includes the tympanic membrane, or eardrum, and the tympanic cavity. The ear drum is a thin tissue that separates the external ear from the middle and inner ear. Once the sound reaches the ear drum it vibrates through air vibration and sends it to the tympanic cavity. The tympanic cavity contains auditory ossicles which are three small bones that vibrate with noise. These bones are the malleus, the stapes and the incus. These bones are connected and are located just behind the ear drum to the window of the inner ear. Unless the ear drum is ruptured, the middle and inner ear is not visible. To keep the ear pressure normal, the middle ear is connected to the pharynx by the eustachian tube. This allows air to pass in and out from the pharynx to the middle ear.
The inner ear is locatated by the petrous temporal bones of the skull. It contains cilia, which arew tiny hair-like strands that are responsible for changing sound impulses into electronic impulses. The inner ear houses a bony labyrinth or osseous that contains fluid filled membranes. There are three structures that are in the inner ear: the cochlea, vestibule and three semicircular canals. The cochlea contains nerves that pass on the sound impulses that are responsible for hearing. The vestibule and the semicircular canals are tissues that are responsible for equilibrium and balance maintenance. The cochlea, the vestibule and the semicircular canals are full of cranial nerves which transmit sound and balance to the brain.
When puppies are born they are not able to hear. Their eardrums are closed until they are 10 days old. They can start to hear sound in about 14 days. At 4 weeks their inner ears are fully developed and a veterinarian can then check for deafness. Deafness results in the damage to the ear drum, the middle and inner structures or the nerves. Disease, trauma or certain drugs can cause deafness in your dog. Deafness can also be hereditary and can affect certain breeds such as Dalmatians, Boston Terriers, Rottweilers and Border Collies.
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Royal Veterinary Centre
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