Picture of the internal ear
Ear – the hearing organ
The three sections of the ear are the outer ear (the part we see), the middle ear, and the inner ear. The ear has a fourth functional part – the auditory cortex of the brain.
How do we hear?
The external ear helps concentrate the vibrations of air on the ear drum and make it vibrate. A chain of little bones in the middle ear transmits vibrations to the inner ear. There they stimulate the fibers of the auditory nerve to send impulses to the brain.
The external ear concentrates air vibrations on the ear drum and makes the drum vibrate.
The middle ear manages equilibrium and transmits the ear drum vibrations to the inner ear.
The internal ear is complex.
The essential component of the inner ear for hearing is the membranous labyrinth. The fibers of the auditory nerve end. This nerve connects the ear to the brain. The membranous labyrinth is a system of communicating sacs and ducts, filled with fluid.
The membranous labyrinth is lodged within a cavity called the bony labyrinth. At some points the membranous labyrinth is attached to the bony labyrinth. At other points the membranous labyrinth is suspended in a fluid within the bony labyrinth.
The bony labyrinth has three parts:
- a central cavity (the vestibule),
- semicircular canals (which open into the vestibule) and
- the cochlea (a snail-shaped spiral tube).
The membranous labyrinth has a vestibule which consists of two sacs, connected by a narrow tube.
The utriculus, the larger of the two sacs, is the principal organ of the vestibular system. It informs us about the position and movement of the head.
The little sac, the sacculus, is connected with a tube in the cochlea. It contains the organ of Corti. Corti is situated in the hair cells, the special sensory receptors for hearing.
Source: MedicineNet, Inc.