Session 7: Functional Anatomy and Disorders of the Ear Flashcards
Three parts of the ear.
External
Middle
Inner
Common symptoms and signs of ear disease.
Otalgia Discharge Hearing loss Tinnitus Vertigo Facial nerve palsy
What are the parts of the external ear?
Pinna and external auditory meatus
What is the external ear lined with?
Skin
Contents of the middle ear.
Air filled cavity containing the ossicles.
What is the middle ear lined with?
Pseudostratified columnar epithelium
What are the three ossicles?
Malleus Incus Stapes
What separates the external ear from the middle ear?
The tympanic membrane
Contents of the inner ear.
Cochlea (hearing) Semicircular canals (balance)
What is the inner ear filled with?
Fluid
How does the inner ear communicate with the middle ear?
Cochlea communicates with the stapes by vibration of the stapes leading to vibration of the fluid in the cochlea.
What else does middle ear communicate with?
The oropharynx
What allows the middle ear to communicate with the oropharynx?
The pharyngotympanic tube also called the eustachian tube.
Why is the eustachian tube important?
It allows air to equilibrate with atmospheric pressure to relieve the negative pressure that would otherwise build up.
What opens the eustachian tube?
E.g. swallowing and yawning
What nerves carry general sensation from ear?
Branches of cervical spinal nerves C2/C3 Vagus nerve Trigeminal nerve (auriculotemporal) Glossopharyngeal nerve (tympanic) Small contribution from facial nerve This can lead to referred pain.
Give examples of other pains that can lead to otalgia.
Tonsils and pharynx Larynx Oropharynx (CN IX) TMJ pain (CN Vc) As well as cancers.
Special sensory of ears (hearing and balance).
Vestibulocochlear nerve
How does the pinna and external auditory meatus differ?
The pinna has elastic cartilage The external auditory meatus is made of bone.
Explain Ramsey Hunt syndrome.
Shingles of facial nerve due to varicella zoster. This leads to facial palsy on one side and a rash in external ear.
What is perichondritis?
Inflammation of perichondrium in pinna of ear.
What is a pinna haematoma?
Accumulation of blood between cartilage and its overlying perichondrium.
What usually causes a pinna haematoma?
Secondary to blunt injury to the pinna common in contact sports.
Pathophysiology of pinna haematoma.
The perichondrium is stripped off the cartilage. The perichondrium has the blood supply and this deprives the cartilage of the blood supply. Instead blood builds up between these layers in a subperichondrial space. This also leads to pressure necrosis of the tissue.
How is pinna haematoma treated?
By drainage of the blood as well as cotton rolls on either side of the pinna to pinch the perichondrium and make it re-apposition of the two layers to each other.
What happens if the pinna haematoma isn’t treated?
Fibrosis of the ear and new asymmetrical cartilage develops to cause what is called a cauliflower deformity.
How long is the external acoustic meatus?
2.5 cm
What is the shape of the external ear?
Sigmoid shape
What serves as a barrier to foreign objects in the ear?
Hair Sebaceous glands Ceruminous glands The bony part lacks these glands and hairs
What is another purpose of the ceruminous glands?
To produce ear wax
Explain the self-cleaning function of the external acoustic meatus.
Desquamation and skin migration laterally off tympanic membrane out of canal by epithelial migration. Mixes with wax to shed out of the ear.