Ear Flashcards
Describe the divisions of the ear
Outer
- auricle, external auditory meatus and external surface of tympanic membrane
Middle
- Internal surface of tympanic membrane, tympanic cavity, ossicles, pharyngotympanic tube
Inner
- auditory/vestibular apparatus, internal auditory meatus, CN VIII, ovala and round window
within which bone is the inner ear found?
Petrous temporal bone
Where does lymph from the auricle drain?
Parotid and cervical nodes
What supplies the auricle with blood?
Branches of ECA
- Superficial temporal
- Anterior auricular
- Posterior auricular
- Perforating branches
Describe the innervation of the auricle?
Facial - Helix, lobe, behind ear CN IX/X - Towards ear cavity CNV3 Auriculotemporal - Anterior to ear
What is the lateral 3rd of the EAM?
Elastic cartilage
What is the medial 2/3rd EAM?
Bone lined with stratified squamous epithelium
Where does the EAM run?
From opening in auricle to petrous temporal bone and tympanic membrane
Describe the innervation of EAM ?
Mainly auriculotemporal CNV3
some branches of CN VII, X
What epithelium is on the outer surface of the tympanic membrane?
Stratified squamous
What structure runs across the tympanic membrane?
Chorda tympani
Describe the innervation of the tympanic membrane
Lateral surface = CNV3, auricular branch of CN X
Medial surface = tympanic branches of CN IX
Name the ossicles.
What joint type exists between each?
Malleus
Incus
Stapes
Synovial plane joints
Origin, insertion, action and innervation of tensor tympani
O - Wall of auditory tube
I - Handle of malleus
A - Tenses TM
I - CNV3
Origin, insertion, action and innervation of stapedius
O - Pyramid of middle ear
I - Neck of stapes
A - Pulls footplate of stapes laterally
I - CN VII
What gives sensory innervation to tympanic cavity?
CN IX
What does chorda tympani supply?
Parasympathetic supply to sublingual and sub-mandibular salivary glands
Special sensory - Taste to anterior 2/3rds tongue
Describe the lining of the medial and lateral sections of auditory tube
Lateral 1.2cm = bony canal
Medial 2.5xm = cartilaginous and membranous
Is the auditory tube usually open?
Closed, opened by contraction of tensor veli palatini
What is the sensory innervation to the auditory tube?
CN IX
Blood supply to middle ear?
Ant tympanic artery from 1st part maxillary
also contributions from ascending pharyngeal, middle meningeal and posterior auricular arteries
Name the bony labyrinths
Cochlea
SCC
Vestibule
Where are the labyrinths found?
Inner ear
What is the membranous labyrinth surround by and what does it contain?
surrounded by perilymph
contains endolymph
conduct sound vibrations and response to changes in acceleration/movement
Explain how sound passes to the cochlea
vibration from footplate of stapes to oval window, vibration at oval window causes a wave of movement to pass into perilymph of Scala vestibule which ascends to top of cochlea then back down to round window.
Round window vibrates into middle ear and sound dissipates
Which structure detects movement and balance?
SCC
utricle and saccule
What is the crust ampullaris and where is it found?
equilibrium receptor that response to rotational movement of the head
found in the ampulla
Whta is within the vestibule?
utricle and saccule
Maculae - respond to change in head position
Describe the arterial supply to the inner ear
Branches of internal auditory/labrynthine artery
- Common cochlear artery
- Vestibular artery
What is the internal auditory artery a branch of?
Anteroiferior cerebellar (>80%)
Occasionally basilar
