The Normal Ear

Question 1

• What are the three parts of the temporal bone, and what are their functions?

Answer 1

Squamous part
Petrous part – encloses internal ear
Tympanic part – encloses middle ear, includes tympanic bulla (when present)

Question 2

• What is the main cranial nerve involved in hearing?

Answer 2

VIII – vestibulocochlear

Question 3

• What are the functions of the ear?

Answer 3

Locate directional source of sound, collect sound waves and conduct to inner ear, transduction and transmission of impulses to brain, balance and positional sense

Question 4

• What does the external ear contain?

Answer 4

Pinna and external ear canal down to tympanic membrane

Question 5

• What structures are involved in supporting the external ear?

Answer 5

Auricular cartilage, scutiform, annular cartilage, bony acoustic process

Question 6

• Describe the vascular supply of the external ear

Answer 6

Auricular arteries (from internal carotid) & venous drainage to internal maxillary vein

Question 7

• What motor nerves innervate the auricular muscles?

Answer 7

Auriculopalpebral, branch of CN VII facial

Question 8

• What covers the external ear?

Answer 8

Thin, stratified keratinising epidermis containing adnexal structures (hair follicles, sebaceous glands & apocrine (ceruminous) glands

Question 9

• What is contained within the cerumen (secretions in ear canal)?

Answer 9

Exfoliated cells, sebaceous secretions, ceruminous gland secretions, immunoglobulins IgA, IgG & IgM

Question 10

• What is the tympanic membrane?

Answer 10

Stratified keratinised epithelium laterally, cuboidal mucosal epithelium medially, forms the boundary between the external and middle ear

Question 11

• What are the three main parts of the tympanic membrane?

Answer 11

Pars flaccida (dorsolaterally), pars tensa (ventrally) & manubrium of malleus

Question 12

• What is the middle ear?

Answer 12

Tympanic cavity, inside tympanic bulla

Question 13

• What are the three compartments of the middle ear?

Answer 13

Epitympanum – contains auditory ossicles, malleus and incus
Mesotympanum – contains 3rd ossicle stapes attached to oval window, round window & opening to auditory tube
Hypotympanum (or fundus)

Question 14

• What are the associated structures of the middle ear?

Answer 14

Cuboidal columnar epithelial lining & auditory tube (runs to nasopharynx, contains scattered goblet cells)

Question 15

• What is housed within the tympanic bulla?

Answer 15

Sensory receptors (malleus, incus, stapes through the oval window and into the cochlea) of the ear

Question 16

• Which nerves run in or close to the wall of the bulla?

Answer 16

Facial nerve CNVII, branches of facial and vagus CNX (form tympanic nerve) & post-ganglionic fibres of cervical sympathetic trunk

Question 17

• Where is the inner ear located and what does it contain?

Answer 17

Encased in bony labyrinth of petrous temporal bone, contains the cochlea, vestibule & semicircular canals

Question 18

• What are the functions of the inner ear?

Answer 18

Hearing, balance & position and rotation of head in relation to gravitational forces

Question 19

• Which Malassezia species are found in the ear?

Answer 19

Malassezia pachydermatitis