The ear is a multifaceted organ that connects the central nervous system to the external head and neck. This structure as a whole can be thought of as 3 separate organs that work in a collective to coordinate certain functions, such as hearing and balance.
The Outer Ear
The outer ear includes:
- The auricle is also known as the pinna, and it is most commonly referred to as the ear. It is the most obviously visible part of the auditory system.
- The ear is the first part of the body to come in contact with auditory stimuli. Sound waves must pass over the auricle before entering the ear canal.
Auditory canal (also called the ear canal)
The ear canal (external acoustic meatus, external auditory meatus, EAM), is a tube running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum.
Eardrum outer layer (also called the tympanic membrane)
- The tympanic membrane is a vital component of the human ear, and is more commonly known as the eardrum.
- It is a thin, circular layer of tissue that marks the point between the middle ear and the external ear.
- The outer part of the ear collects sound. Sound travels through the auricle and the auditory canal, a short tube that ends at the eardrum.
The Middle Ear
The middle ear includes:
The eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea.
Cavity (also called the tympanic cavity)
The tympanic cavity is an air chamber; it contains a chain of movable bones which transmit the vibrations of the tympanic membrane across the cavity to the middle ear.
The three tiniest bones in the body form the coupling between the vibration of the eardrum and the forces exerted on the oval window of the inner ear. Three tiny bones that are attached
- Malleus (or hammer) – long handle attached to the eardrum
- Incus (or anvil) – the bridge bone between the malleus and the stapes
- Stapes (or stirrup) – the footplate; the smallest bone in the body.
The Inner Ear
The inner ear includes:
- oval opening on the lateral wall of the vestibular labyrinth adjacent to the MIDDLE EAR.
- It is located above the cochlear round window and normally covered by the base of the STAPES.
- Three small, membranous tubes in the bony semicircular canals that lie within the bony labyrinth and form loops of about two thirds of a circle.
- The three (anterior semicircular duct, lateral semicircular duct, and posterior semicircular duct) lie in planes at right angles to each other and open into the vestibule by five openings, of which one is common to the anterior and lateral ducts.
- Each duct has an ampulla at one end within which filaments of the vestibular nerve terminate.
- The inner ear structure called the cochlea is a snail-shell like structure divided into three fluid-filled parts.
- Two are canals for the transmission of pressure and in the third is the sensitive organ of Corti, which detects pressure impulses and responds with electrical impulses which travel along the auditory nerve to the brain.
- The eustachian tube (pharyngotympanic tube) connects the middle ear cavity with the nasopharynx.
- It aerates the middle ear system and clears mucus from the middle ear into the nasopharynx. Opening and closing functions of the eustachian tube are physiologically and pathologically important.
- Normal opening of the eustachian tube equalizes atmospheric pressure in the middle ear; closing of the eustachian tube protects the middle ear from unwanted pressure fluctuations and loud sounds.
- Abnormal or impaired eustachian tube functions (ie, impaired opening or closing, defective mucociliary clearance) may cause pathological changes in the middle ear.This in turn can lead to hearing loss and other complications of otitis media.