Functional Anatomy of the Ear and Disorders Flashcards
Where is the external ear located?
Consists of the pinna/auricle and the external acoustic meatus (ear canal). Extends to the fibrous tympanic membrane medially.
What is the auricle?
Cartilaginous part of the external ear covered in skin wit a fleshy fatty lobule at the inferior end.
Where is the middle ear located?
Where is the inner ear located?
Which bone houses the components of the ear?
Temporal Bone
What are the four parts of the temporal bone?
- Squamous part
- Petromastoid part (petrous and mastoid bone)
- Tympanic plate
- Styloid process
Which bone is the middle and inner ear in?
Petrous part of the temporal bone
What does the upper surface of the petrous bone form the floor of?
Middle and posterior cranial fossa
Where is the interal acoustic meatus?
Within the petrous part of the temporal bone of the skull between the posterior cranial fossa and the inner ear
Which cranial nerves pass through the internal acoustic meatus?
CN VII (facial) and CNVIII (vestibulocochlea)
What opening does the inferior surface of the petrous bone contain?
Carotid canal through which the internal carotid artery enters the skull
Which muscles attach to the mastoid process?
Sternocleidomastoid and digastric muscle
What does the mastoid antrum connect?
Mastoid air cells and the middle ear cavity. Infection of the middle ear can potentially spread to the mastoid process causing mastoiditis.
What does the external ear consist of?
Pinna/auricle
How does a cauliflower ear form?
From an untreated pinna haemotoma.
Label
What is the bony canal of the external ear formed by?
Tympanic plate of the temporal bone
What is the external acoustic meatus lined with?
Skin that secretes cerumen giving the canal protection
How does wax form?
Discarded cells of skin with cerumen
What are the common conditions associated with the external acoustic meatus?
- otitis externa
- wax
- foreign bodies (particularly in children)
What lies most medially at the external acoustic meatus?
Fibrous tympanic membrane
How do you distinguish a right and left tympanic membrane?
The side that the cone of light and the manubrium of mallus points to is the side that it is (picture shows right)
What is another name for the middle ear?
Tympanic cavity
What are the ossicles?
Bones found in the middle ear:
- Malleus
- Incus
- Stapes
What do the ossicles do?
Transmit vibrations from the tympanic membrane to components of the inner ear in an air filled environment.
When does communication between the middle ear and external environment occur?
When the eustachian (pharyngotympanic) tube opens arising from the nasopharynx to the middle ear.
What is the purpose of the pharyngotympanic tube?
To equalise air pressure in the middle ear
When does the pharyngotympanic tube open?
When attached palate muscles are pulled during yawning or swallowing
What is the clinical significance of the pharyngotympanic tube?
Potential route of infection for an upper respiratory infection to travel to the middle ear
What is the middle ear lined with?
Respiratory epithelium (pseudostratified columnar epithelium)
What is the sensory nerve of the middle ear?
Glossopharyngeal nerve (CN IX)
What is mastoiditis?
Rare complication of middle ear infections, osetomyelitis of the mastoid bone
Where can middle ear infections spread to?
- Mastoid
- Meninges
- Temporal lobe (causes an abscess)
- Sigmoid dural venous sinus (causes a septic thrombus to form)
Where do the ossicles lie?
In the upper part of the tympanic membrane
