The human ear is an organ concerned with hearing and equilibrium. It converts sound waves into electrochemical signals that are interpreted by the brain and helps you maintain your sense of balance. Anatomically, the ear can be divided into the outer ear, the tympanic membrane, the middle ear, and the inner ear.
The outer ear consists of the auricle or pinna - the visible portion of the ear that projects from the side of the head - and a short external auditory canal.
The auricle comprises an upper portion made up of elastic cartilage covered tightly by the skin and a lower fleshy portion known as the lobule. The cartilage is molded into ridges and furrows to form an irregularly shaped, hollow funnel. The deepest portion of the auricle which leads into the external auditory canal is called the concha. The concha is partially covered by two small projections: the tragus in the front, and the antitragus behind. The auricle has several rudimentary muscles that attach it to the skull and scalp.
External Auditory Canal
The external auditory canal is a tube extending from the concha to the tympanic membrane. The outer two-thirds of the external auditory canal is made of cartilage and the inner third is bone. Fine hair and modified sweat glands that produce ear wax line the external auditory canal.
The tympanic membrane, also known as the eardrum, is a thin translucent membrane that covers the end of the external auditory canal. It has the shape of a flattened cone with its apex directed inwards and separates the outer ear from the middle ear.
The middle ear is an air-filled cavity divided by a slight constriction into a lower chamber called the tympanic cavity and an upper chamber called the epitympanum. The main structures in the middle ear are the ossicles and the eustachian tube.
Crossing the middle ear is an osseous chain formed by three tiny bones or “ossicles” called the malleus, incus, and stapes. The ossicles help to transmit sound waves to the inner ear.
The eustachian tube connects the middle ear to the back of the nose and helps to equalize pressure in the ear. This allows the proper transmission of sound waves.
The inner ear contains the vestibular system, which is the balance apparatus, and the cochlea, which is the hearing apparatus.
The vestibular system is made up of the vestibule, which contains special organs that respond to gravitational forces, and semi-circular canals which are at 90-degree angles to each other. These canals are filled with fluid and have calcium crystals embedded in their lining. They tell the brain in which direction your head is moving.
The cochlea has an anatomical structure that resembles a snail’s shell. It has two chambers divided by a membrane and is filled with fluid which vibrates when sound waves are carried through the inner ear.
The auditory nerve, also known as the cochlear nerve, arises from the cochlea in the inner ear and carries sound and balance information to the brain.