Ear Functions

Phagryngotympanic/Eustachian Tube

A membranous tube leading from the middle ear to the pharynx. Its function is to equalize the air pressure inside the middle ear with the external air pressure.

External Auditory Canal

A one-inch long tube extending medially into the temporal bone and terminating at the eardrum. The skin lining contains hair follicles and wax-secreting glands. Earwax, or cerumen is a yellowish waxy substance secreted in the ear canal. It protects the skin of the ear canal, assists in cleaning and lubrication, and also provides some protection from bacteria, fungi, insects and water.

Auricle (Pinna)

A skin covered cartilaginous structure encircling the opening to the external auditory canal. The pinna directs the sound into the ear canal.

Middle Ear

A small air-filled cavity inside the temporal bone. It extends from the tympanic membrane to the inner ear. Includes the ossicles

Tympanic Membrane (Eardrum)

A thin, membranous partition that separates the external and middle ears. Sound vibrations funneled through the external auditory canal cause the tympanic membrane to vibrate. Function of the eardrum is to carry sound waves to bones that are located in the middle ear. These bones are called ossicles.

Inner Ear: a. Cochlea b. Vestibule c. Semicircular canals

contains specific receptors involved in hearing and balance a. a snail-shaped structure within the temporal bone. Sound vibrations are transferred to the fluid in the cochlea via the stapes at the oval window; termination is at the round window. The cochlea contains the receptors involved in hearing. b. intermediate area between the cochlea and the semicircular canals. The fluid-filled vestibule contains receptors involved in static equilibrium and sensing of linear acceleration of the head. c. a series of three fluid-filled channels oriented at right angles to each other. These canals contain receptors involved in sensing of angular acceleration of the head.

Oval Window

separates the middle ear from the fluid-filled cochlea. The stapes initiates vibration of cochlear fluid via the oval window.

Round Window

separates the terminal portion of the cochlea from the middle ear. Vibrations conducted through the cochlea end here.

Ossicles: a. Malleus (hammer) b. Incus (anvil) c. Stapes (stirrup)

three small bones, linked in series, that span the middle ear. They transfer sound vibrations from the tympanic membrane to the inner ear at the oval window. a. attached to the tympanic membrane, receives vibrations from the tympanic membrane and transmits this to the incus. b. middle bone, incus receives vibrations from the malleus and transmits these to the stapes. c. most medial of the ossicles, transfers vibrations via its footplate to the oval window