Lecture 5: Ear Flashcards
Surface structures of the ear? EAM?
The external acoustic meatus is NOT straight
- the lateral 1/3 is cartilagenous
- medial 2/3 is bony tunnel
Innervation of the external ear?
Mainly from CN V3 and some X
- Auricle is superficially supplied by the cervical plexus, V3 and deeper parts by X and VII
- EAM by V3, X and VII
- Tympanic membrane outer surface by V3, X, VII and IX
- Tympanic membrane inner surface by IX
Where is the middle ear located?
- Within the petrous part of the temporal bone
- separated from the middle cranial fossa by the tegmental wall
Floor of the middle ear?
The Jugular wall (internal jugular vein)
Tympanic branch of the IX - glossopharyngeal enters and forms a plexus along with the lesser petrosal nerve (PS supply)
Lateral wall?
Membranous wall = tympanic membrane + epitympanic recess
Separates from EAM and is the most important to us.
Outer surface innervated by V3 (with X and VII) and inner surface by IX
Medial wall?
Labrynth wall
- Promontry where the
- tympanic plexus sits
- Oval and round wall
- lesser petrosal nerve and b of int carotid plexus
The facial canal is where the facial nerve travels after coming out the internal acoustic meatus before giving off the chorda tympani and then traveling through the stylomastoid foramen.
Anterior wall?
Carotid wall
- Pharyngotympanic tube (too nasopharynx - eustachian tube)
- Tensor tympanic muscle
- corda tympani nerve (exits via ant wall)
- Carotidotympanic nerves
Posterior wall?
Mastoid wall
- Stapes tendon
- corda tympani nerve (enters here and runs along the tympanic membrane to the anterior wall)
The aditus to mastoid antrum lies on this wall to get to the mastoid antrum and the air cells (outside the middle ear)
Contents of the middle ear?
Bones = malleus, incus and stapes
Tendons and muscles = stapedius and tensor tympani
Nerve branches of the tympanic plexus
