L16: Ear Flashcards
Divisions of ear
- External, middle (aka tympanic cavity) and inner ear
Cartilage of ear auricle
- Elastic cartilage
Parts and Function of auricle
- Collect sounds waves and pass them to ext auditory meatus - Helix - Anti-helix - Lobule - Tragus
Parts of the external ear
- Auricle - External auditory meatus - Tympanic membrane
Glands of external auditory meatus
- Ceruminous glands – produce cerumen
Describe the external auditory meatus from a structural standpoint
- Lateral 1/3rd is cartilaginous - Medial 2/3rd is bony
Nerve supply of external auditory meatus
- Auriculotemporal (CN V3) - Vagus nerve
Blood supply to external acoustic meatus?
- Deep auricular branch of maxillary artery
Coverings of TM
- Outside = skin - Inside = mucus membrane
Central depression of TM – function?
- UMBO: attachment of handle of malleus
Quadrants of TM
- Anterosuperior - Anteroinferior: contains cone of light - Posteroinferior - Postersuperior
Which quadrant of the TM shows the cone of light?
- anteroinferior
Nerve supply to TM
- Auriculotemporal (external surface) – from CN V3 - Tympanic branch of CN IX (internal surface)
Structures of the middle ear/tympanic cavity?
- Opening of Eustachian (pharyngotympanic/auditory) tube - Ossicles (malleus, incus, stapes) - Tensor tympani m - Stapedius m - Oval and round windows - Tympanic plexus
In what bone is the middle ear located?
- Petrous portion of temporal bone
Explain divisions of tympanic cavity
- Roof: thin layer of temporal bone called tegmen tympani - Floor: above carotid canal and beginning of int jugular vein - Posterior wall: entrance to mastoid air cells and entrance of stapedius muscle and chorda tympani - Lateral wall: tympanic membrane - Medial wall: tympanic plexus, oval and round windows - Anterior wall: separation from carotid canal, has opening to Eustachian tube
What is the tegmen tympani?
- roof of tympanic cavity formed by thin layer of temporal bone
What CN forms the tympanic plexus?
- CN IX
What structure does the stapes connect with on its medial side?
- Oval window
What does the tensor tympani m attach to?
- Handle of malleus
What does the stapedius m attach to?
- Neck of stapes
Innvervation of tensor tympani and stapedius muscles?
- Tensor tympani: CN V3 - Stapedius: CN VII
Two parts of inner ear
- Vestibular portion - Auditory portion
Divisions of labyrinth/inner ear. Describe each
- 1.) Bony labyrinth: a.) Vestibule: oval cavity which communicates anteriorly with cochlea and posteriorly with semicircular canals b.) Cochlea: bony snail-like structure coiled 2.25 times around pillar known as modiolus c.) Semicircular canals: three of these forms 2/3 of a circle and communicate with vestibule - 2.) Membranous labyrinth: membranous duct system located in bony labyrinth, contains endolymph. Consists of cochlear duct, three semicircular ducts and two sacs called utricle and saccule
Function of tensor tympani and stapedius muscles?
- Dampen vibration of ossicles
