Flashcards in Anatomy of the Ear and Auditory Tube Deck (24):
What anatomical landmarks distinguish the borders of the outer, middle and inner ear respectively?
Outer: from auricle to tympanic membrane
Middle: from tympanic membrane to round and oval windows
Inner: cavity extending into the petrous part of the temporal bone from the round and oval windows
What is the role of the auricle?
Cartilaginous structure which helps to collect sound
Describe the nervous supply of the external acoustic meatus
Vagus supplies the posteroinferior walls
Auriculotemporal (from CNV3) supplies anterosuperior walls and external surface of tympanic membrane
What is the significance of the nerve supply of the tympanic membrane?
Pain can be referred to or from other branches of CNV3 (e.g. lower teeth)
What lines the external acoustic meatus and why?
Hairy skin and cerumen glands to prevent maceration of the skin with water
Describe the structure of the external acoustic meatus
Lateral 1/3 is cartilaginous
Medial 2/3 is bony (temporal bone)
What is the role of tympanic membrane?
Vibrates with the frequency and amplitude of the incoming sound to transfer this sound through to the inner ear via the ossicles
What is the significance of the "cone of light" seen through an oroscope when examining the tympanic membrane?
Should be located in the anteroinferior quadrant; light reflecting elsewhere may indicate a pressure build-up behind the tympanic membrane
What is the epitympanic recess?
An opening above the tympanic membrane that communicates posteriorly with the mastoid air cells
What is the role of the auditory tube?
Projects anteroinferiorly to the nasopharynx allowing for equalization of pressure to the middle ear and drainage of inflammatory exudate
What is the difference between the auditory tube in childhood and adulthood and how is this clinically relevant?
More horizontally orientated in childhood, meaning drainage is more difficult and children are therefore more prone to infections of the middle ear
These infections can affect hearing as the mucus stifles the movement of the ossicles
What is the name of the main cavity in the middle ear?
Tympanic cavity proper
What are the 3 ossicles of the middle ear, in order of most lateral to most medial?
Malleus, incus, stapes
What is the name of the process projecting from the malleus that communicates with the tympanic membrane?
What is the name of the process projecting from the body of the incus to articulate with the head of the stapes?
What is the role of the stapedius and tensor tympani muscles?
To dampen the amplitude of vibration when the volume of sound is excessive
Which nerve innervates stapedius?
Which nerve innervates tensor tympani?
Where does stapedius attach?
Where does tensor tympani attach?
Which ossicle overlies the oval window?
Describe the course of the internal carotid artery
Runs straight underneath the middle ear through the carotid canal, and makes an S-shaped bend at foramen lacerum
Describe the structure of the inner ear
A bony labyrinth filled with perilymph, containing a membranous labyrinth filled with endolymph