Anatomy of the ear

Question 1

LOs:

• Identify the cartilaginous structures of the outer ear
• Describe the innervation, vascularisation and lymphatic drainage of the external ear
• Explain how the temporal bone contributes to the structure of the inner amd middle ear
• Describe the structure of the pharyngotymanic tube, its function, and how disruption of its function can result in clinical conditions
• Describe the structures composing the walls of the tympanic cavity and their anatomical relations
• Describe the structure and features of the auditory ossicles, and how their interaction contributes to their function
• Describe the structures of the bony and membranous labyrinths, and explain how these relate to their functions
• Recall the course of the facial nerve and vestibulocochlear nerves through the ear and the clinical reults of disruption of this passage
• Apply common clinical conditions affecting the ear to the functional anatomy of the ear

Question 2

the ear can be divided into 3 main parts:

Answer 2

External ear- includes the pinna and the external auditory canal. It ends at the tympanic membrane.

Middle ear- lies within the temporal bone and contains the ossicles (malleus, incus and stapes), segments of the facial nerve (CN VII) and the Eustachian tube

Inner ear- contains the cochlea, vestibule and semi-circular canals

Question 3

Bone anatomy- the temporal bone

it can be divided into how many segments?

what are they?

Answer 3

The temporal bone forms the inferolateral walls of the skull and houses the middle and inner parts of the ear. It can be divided into 6 segments:

1. Squamous part- flat plate, contributes to the temporal fossa
2. Petrous part- pyramidal projection pf the temporal bone, containing the inner ear structures and segments of the facial nerve (CN VII)
3. Tympanic segment- contains the bony portion of the external ear canal
4. Zygomatic process- forms the zygomatic arch with the zygomatic bone
5. Styloid process- projects inferiorly, sit of attachment for various muscles and ligaments
6. Mastoid process- houses the mastoid air cells? Insertion point for sternocleidomastoid muscle

Question 4

consequences of fracturing the temporal bone

Answer 4

Fracture of the temporal bone can cause conductive or sensorineural hearing loss.

As the temporal bone also contains portions of the facial nerve disruption of the external+/ middle ear can lead to conductive hearing loss e.g., obstruction of ear canal by blood

Disruption of the inner ear structures can cause sensorineural loss.

Look for battle sign- bruising in the postauricular region suggestive of a skull base fracture