Middle Ear

Question 1

What is the sensory supply to the external auditory meatus?

Answer 1

• auriculotemporal nerve (CN V3)
• auricular branch of the vagus nerve
• branches of facial nerve.

Question 2

What is the blood supply to the external ear?

Answer 2

posterior auricular artery
superficial temporal artery
deep auricular branch of the maxillary artery

Question 3

What makes up the external auditory meatus?

Answer 3

3-cm-long sinuous tube. The lateral third is

cartilaginous; the medial two-thirds are bony.

Question 4

Contents of the middle ear?

Answer 4

3 ossicles: malleus, incus and stapes
3 nerves: facial nerve, chorda tympani and tympanic plexus
2 muscles: stapedius and tensor tympani
eustachian tube: the distal opening is in the nasopharynx

Question 5

What is the origin of the chorda tympani?

Answer 5

Facial nerve

Question 6

What does the chorda tympani supply?

Answer 6

Taste to anterior 2/3 of tongue
Secretomotor function to submandibular and sublingual
glands.

Question 7

What is the principle of sound transmission in the middle ear?

Answer 7

Ossicles conduct vibrations from tympanic membrane to the oval window of cochlea. This continues as pressure waves in fluid of cochlea.

Question 8

How can middle-ear infections spread to the skull vault?

Answer 8

Eustachian tube allows infection to pass from nasopharynx to middle ear - otitis media.
Otitis media can spread into adjacent mastoid air
cells (antrum via aditus). These are separated from
cerebellum and temporal lobe only by thin
bone, can lead to meningitis and cerebral abscesses.

Question 9

Boundaries of middle ear

Answer 9

Roof: Tegmen tympani (v thin) petrous temporal bone- temporal lobe of middle cranial fossa
Floor: Jugular wall- internal jugular vein
Medial: Internal carotid artery
Lateral: Tympanic membrane
Anterior: Eustachian tube
Posterior: Mastoid antrum