The ear Flashcards
What are the bones of the tympanic cavity?
Malleus
Incus
Stapes
What is the role of the tensor tympanii muscle?
Tenses the tympanic membrane
Describe the bony component of the inner ear
Surrounded by the otic capsule which is a very dense bone within the petrous portion of the temporal bone
The bony labarynth is a system of bony canals filled with perilymph made up of the cochlea, vestibule and semicircular canals
What ossicle is attached to the inner surface of the tympanic membrane?
Malleus
Describe how vibration passes from the middle ear to the inner ear
Passes from the footplate to the oval window. The window vibrates and sends the sound waves to the perilymph of the scala vestibuli
The scale vestibuli ascends to the top of the helicotrema then the wave passes to the scala tympani which transports it to the round window
What fluids of the inner ear conduct sound vibrations?
Perilymph (boney and membranous components)
Endolymph (membranous)
What are the attachments of the stapedius muscle and what is its innervation?
Origin - pyramid of the middle ear
Inserts - neck of stapes
CN VII
What is the function of the auricle?
Catches sound waves and funnels them toward the external auditory meatus
What is the role of the eustacian tube?
Equalises pressure on both sides of the tympanic membrane
What are the 2 muscles of the inner ear?
Tensor tympani
Stapedius
What lines the tympanic membrane?
Outer surface = stratified sqaumous epithelium,
Inner surface = covered by a mucous membrane
What do the cells of the organ of corti do?
Detect movement and transform it to a nerve impulse to the cochlear nerve
What is the role of the stapedius muscle?
Pulls the footplate of the stapes laterally
What are the attachments and innervation of tensor tympanii?
Origin- wall of auditory tube
Inserts- handle of the malleus
CN V3
What branch of CNVII crosses the medial surface of the tympanic membrane?
Chorda Tympani
What is housed within the ampulla of the semicircular canals?
Equilibrium receptors called crista ampullaris. Respond to angular movements of the head
What equilibrium cells are present within the urticle and saccule?
Maculae - respond to the pull of gravity and changes in head position
What is the sensory innervation of the eustacian tube?
CN IX
Describe the structure of the external auditory meatus?
Tubular structure around 2.5cm. Runs from the opening of the auricle into the petrous bone and ends at the tympanic membrane
Lateral 1/3 - elastic cartilage, hair follicles, sweat and sebaceous glands
Medial 2/3 - bone lined with stratified sqaumous epithelium
What is the membranous component of the inner ear?
A continuous system of ducts and sac inside the bony labyrinth of the inner ear
What structures of the ear belong in the external portion?
Auricle
External auditory meatus
External surface of the tympanic membrane
Describe the role and path of the chorda tympanii nerve?
Leaves tympanic cavity via the petrotympanic fissure and joins the lingual nerve
Parasympathetic - supplies the sub-lingual and sub-mandibular glands
Supplies taste to anterior 2/3 of tongue
Describe the eustacian tube?
Connects the nasopahrynx with the tympanic cavity
Lateral aspect - bony canal lined with mucosa
Medial aspect - cartilagenous, membranous tube
What are the 3 semicircular canals of the ear?
Anterior, posterior and lateral
Anterior and posterior are at right angles
lateral is horizontal
What is the arterial supply to the auricle?
Recieves blood from branches of the ECA
- Superficial temporal
- Anterior auricular
- Posterior auricular
What type of cartilage forms the external ear?
Elastic cartilage - allows ear to be bent without being damaged
What structures of the ear are found in the inner compartment?
Auditory apparatus Vestibular apparatus Internal auditory meatus CN VIII Oval and Round window
True or False?
The eustacian tube is usually open
False
Usually closed but opens when the tensor veli palatini contract (yawning, swallowing etc.)
What is the combined action of the muscles of the inner ear?
Dampen the sound being passed from the ossicles to the more delicate inner ear structures
What is the innervation of the tympanic membrane?
Lateral surface - auriculotemporal nerve (CNV3) and the auricular branch of the vagus (CNX)
Medial surface - tympanic branches of glossopharyngeal nerve (CN IX)
