Anatomy of a Cat's Ear

The cat ear, a sense organ dedicated to hearing and balance, is divided into three sections: the outer or external ear, the middle ear and the inner ear. Each section consists of one or more anatomical components serving specific functions. Cat ears are located on either side of their head, above and behind the eyes, and can be identified by their erect outer portion, also known as the pinna.

  1. External/Outer Ear

    • The outer ear is made up of the pinna or auricle and the ear canal. The former is the visible, fur-covered, funnel-shaped part of the ear that collects sound and directs it down the ear canal. The ear canal is an L-shaped narrow passage through which sounds travel that terminates at the ear drum.

    Middle Ear

    • The middle ear consists of the eardrum or tympanum and the bony tympanic cavity, also known as the osseous bulla, which contains the three tiny bones called ossicles. These three bones are often referred to as the hammer, the stirrup and the anvil, because they resemble these tools, but their technical names are the malleus, stapes and incus. The middle ear is connected to the inner ear through the oval window, as well as to the back of the throat, or pharynx, through the eustachian tube. The air flow between the pharynx and middle ear stabilizes the pressure within the middle ear.

    Inner Ear

    • The inner ear is housed in the bony labyrinth and consists of three structures: the cochlea (spiral tube), which transmits electrical impulses related to hearing along nerves to the brain; the vestibule, which transfers information regarding bodily position; and the three semicircular canals, which transfer information to the brain about the body's motion.

    Hearing

    • Hearing is the result of sound waves in the air traveling through the ear, creating vibrations within the parts of the ear, and these vibrations being converted into electrical signals that travel along nerves to the brain. The sound waves enter through the pinna and the ear canal. They cause the eardrum to vibrate, which in turn causes the three bones of the inner ear to vibrate. These vibrations are changed into electrical signals by the cochlea and then travel to the brain along the vestiblocochlear nerve.

    Balance

    • The ear also helps to maintain balance. The fluid inside the three semicircular canals moves as the head moves. This movement is converted into electrical impulses that send information to the brain about the direction and amount of movement. The vestibule is sensitive to gravity and sends information about the position of the head when it is being held still.