The Ear Flashcards
What are the roles of the ear?
Hearing
Balance
What are the 3 main divisions of the ear?
External
Middle
Inner
Where can referred pain to the ear be from? What nerves are responsible?
Mandible and mandibular teeth (Vc)
Temporomandibular joint (Vc)
Laryngopharynx (X)
Larynx (X)
Cardiac (X)
Pharynx (IX)
What is the purpose of the auricle and pinna?
Capture sound waves and direct them into the ear
What is the sensory innervation of the external acoustic meatus?
CNVc and X
How should an examination of the ear be performed in an adult?
How is the external acoustic meatus directed in an adult?
Pull pinna posterior and superior to straighten out and examine.
The EAM in an adult is S shaped and directed antero-inferiorly.
How should examination of the ear be performed in a child?
How is the external acoustic meatus directed in a child?
Pull ear posterior and inferiorly to straighten out and examine.
EAM in a child is almost horizontal
How should the tympanic membrane appear on examination?
Concave
Cone of light pointing anterior and inferior
How can pathology change the appearance of the tympanic membrane?
Can cause convexity or increased concavity.
Green suppuration
Visible redness from inflammation
Describe the 3 layers of the tympanic membrane What is the sensory innervation of each layer?
Outer skin: CN Vc and X
Mesoderm
Inner respiratory mucosa: CN IX
Where can pain refer from/to the tympanic membrane? What is the innervation?
Outer skin layer (Vc and X):
- Mandible/mandibular teeth
- Temporomandibular joint
- Laryngopharynx
- Larynx
- Cardiac
Inner layer (CNIX):
- Pharynx
What is the sensory innervation to the middle ear and auditory tube?
CNIX
Where does CNIX supply sensory innervation to?
Middle ear and auditory tube
Inner layer of tympanic membrane
All portions of the pharynx
Where does the nasopharynx receive sensory innervation from?
CNVb
CNIX
Where does the laryngopharynx receive sensory innervation from?
CNIX and X
Where does the oropharynx receive sensory innervation from?
CNIX
What does damage to the ossicles of the middle ear cause?
Conductive hearing loss
What is the role of the ossicles of the middle ear?
Link tympanic membrane to the oval window
Amplify signal from tympanic membrane
What type of joint is between the ossicles of the middle ear?
What prevents dislocation?
Mobile synovial joints
Ligaments prevent dislocation
What are the bones of the middle ear?
From tympanic membrane to oval window:
- Malleus
- Incus
- Stapes
What are the muscles of the middle ear and their roles?
Control oscillatory ranges of the ossicles.
Tensor tympani:
- Originates from bony canal above pharyngotympanic tube and inserts into neck of malleus
- Pulls tympanic membrane taut (medially) to reduce force of vibrations
Stapedius:
- Passes from pyramidal eminence to stapes
- Pulls stapes, limiting its range of movement in response to large vibrations.
What is the innervation of the middle ear muscles?
Stapedius: CNVII
Tensor tympani: CNVc
What are the walls of the middle ear?
Lateral wall: Tympanic membrane
Inferior wall: Jugular wall (separates from jugular vein)
Roof: Petrous part of temporal bone (separates middle ear from middle cranial fossa)
Medial wall: Formed by lateral wall of inner ear
Posterior wall: Mastoid wall (partition between middle ear and mastoid air cells)
- Contains hole called aditus to mastoid antrum
Anterior wall: bony plate with 2 openings:
- Auditory tube
- Tensor tympani muscle
- Separates middle ear from internal carotid artery
How can a middle ear infection cause mastoiditis?
Spread through the posterior wall of the middle ear into mastoid air cells through the aditus to the mastoid antrum
