• provides the senses of equilibrium and hearingequilibrium- informs us of the position of the body in space by monitoring gravity, linear acceleration, and rotation.hearing- enables us to detect and interpret soundwaves.
3 Anatomical Regions of the Ear1. External Ear2. Middle Ear3. Inner Ear
The External Auditory Meatus- Extends from the concha to the tympanic membrane.- Its length, from the floor of the concha, is approximately 2.5 cm and from the tragus about 4 cm.- It has two structurally different parts, the lateral third being cartilaginous and the medial two-thirds osseous.
The External Auditory Meatus• Features:1. skin2. Hair3. Sweat Glands4. Sebaceous Glands /Ceruminous Glands -slows down the growth of bacteria and reduces the chances of infection
Tympanic Membrane- separates the external and middle ear- transmits soundwaves along the auditory ossicles to the inner ear.- the deepest part of which is the umbo where the tip of the handle of the malleus is attached.
Middle Ear- also known as the tympanic cavity- space in the petrous temporal bone lined by mucous membraneThe cavity has two parts:1. the tympanic cavity proper, opposite the membrane, and2. an epitympanic recess, contains the malleus and incus.
Walls of the Middle EarAnterior - opens directly to the eustachain tubePosterior - presents a large opening - aditus - that leads to the tympanic antrum, where the stapedius m. is found.Lateral - tympanic membraneMedial - foramen ovale of the vestibuleRoof - tegmen tympani
The Bony Labyrinth1. Bony Labyrinth - about 3 mm. thick that is as hard as ivory. 3 parts: a. Vestibule b. Semicircular Canals c. Cochlea
The Vestibule of the Bony Labyrinth- the central part of the bony labyrinth behind the cochlea containing the fenestra vestibuli enclosed by the stapes.- contains the utricle and saccule which contain receptors for the sensation of gravity and linear accelaration.
The Semicircular Canals- 3 horseshoe- shaped fluid- filled canals that contain receptors stimulated by the rotation of the head.
The Cochlea - the bony cochlea contains the cochlear duct of the membranous labyrinth.- contains receptors in the cochlear ducts that provide the sense of hearing.
Membranous labyrinth- lies within the bony labyrinth and consisting of sacs that contain fluid known as endolymph.- The fluid that separates the bony and membranous labyrinth is known as perilymph. This is made up of: a. Scala Tympani b. Scala Vestibuli c. Cochlear duct - organ of corti