The ear is split into 3 sections
The external ear
What is the pinna and whats it made of?
Also called the auricle, its the visible part of the ear residing outside the head.
Its made of elastic cartilage and covered in stratified keratinized epithelium (skin)
Describe the lateral 1/3rd of the external ear canal?
Its made of skin and cartilage like the auricle.
It has ceruminous and sebaceous glands that produce wax
What is the function of the lateral 1/3rd of of the external ear canal and wax?
The lateral 3rd acts as a protective/disinfectant barrier.
Skin gets trapped here in the wax and sheds as a cleaning mechanism
How serious is an external ear obstruction?
Wax or other mechanical obstruction have a minimal effect on hearing loss compared to middle or inner ear problems
What is the tympanic membrane?
A triple layered membrane dividing the external ear canal and the middle ear
Layers of the tympanic membrane?
Outer layer - Continuous with the skin of the EAC, in fact its grows out from the umbo at the centre of the tympanic membrane
Middle layer - Fibrous
Inner Layer - resp. epithelium (Ciliated Columna Epithelium + Goblet Cells)
What can you see through the tympanic membrane?
Handle of the malleus
What are the important parts of the middle ear?
The 3 ossicles:
- Small bones that carry sound from the tympanic membrane -> Inner ear
- Malleus -> Incus -> Stapes
- The stapes foot plate sits against the oval window through to the inner ear
The chorda Tympani comes from the facial nerve and loops around the short process of the malleus.
Describe the epithelium of the middle ear?
Ciliated Columnar Epithelium + goblet cells
What are the connections of the middle ear?
Mastoid air cells
Nasopharynx via eustachian tube
Whats the clinical relevance of the middle ear?
- The ossicles can be damaged by trauma or osteosclerosis
- Otitis media
What is a cholesteatoma?
An invasion of keratinized squamous epithelium through the tympanic membrane into the middle ear
What are the important relations of the middle ear?
- Middle Cranial Fossa
- Sigmoid Sinus
- Facial Nerve
- Mastoid Cavity
- Inner Ear
What are the segments of the facial nerve?
- Meatal (passing through the internal auditory meatus)
- Labyrinthine segment
- Tympanic Segment
- Mastoid Segment
- Extratemporal segment (section outside the stylomastoi foramen)