Anatomy of the middle ear. Flashcards
What is the function of the middle ear ?
To transmit vibrations picked up from the tympanic membrane to the inner ear, which it does using 3 bones (known as the auditory ossicles):
What are the 3 auditory osciles ?
1- Malleus (also known as the “hammer”)
2- Incus (also known as the “anvil”)
3- Stapes (also known as the “stirrup”)
What is the oval window ?
Oval window – attachment point for the base of the stapes to transfer vibrations from ossicles to the cochlea
What is the Round window ?
Round window – bulges outwards during hearing and is the site where a cochlea implant would usually enter the cochlea.
What tube is present within the middle ear ?
The Eustachian/auditory/pharyngotympanic tube.
Explain where vibrations from the tympanic membrane pass …
1- Tympanic Membrane
2- Malleus
3 - Incus
4 - Stapes
5 - oval window - This transfers vibrations over to the inner ear.
The ossicles of the middle ear are held in position mainly by ligaments which allow them to articulate with each other.
What are these middle ear muscles ?
1- Tensor tympani - Attaches to the malleus. It can contract and tense the tympanic membrane in response to loud noises.
2- Stapedius - The stapedius attaches onto the neck of the stapes. Contraction of this pulls the stapes posteriorly. This prevents excessive oscillation on the oval window, usually in response to loud noises.
What do the mastoid air cells do ?
The mastoid air cells are located posterior to epitympanic recess. They are a collection of air-filled spaces in the mastoid process of the temporal bone. The air cells are contained within a cavity called the mastoid antrum. The mastoid antrum communicates with the middle ear via the aditus to mastoid antrum.
The mastoid air cells act as a ‘buffer system‘ of air – releasing air into the tympanic cavity when the pressure is too low.
