Ear & Taste Anatomy Flashcards
Name the 5 foraminae in the temporal bone
- External acoustic meatus
- Internal acoustic meatus
- Stylomastoid foramen
- Petrotympanic fissure
- Extracranial opening of carotid canal
What 2 structures make up the external ear?
- Pinna (auricle)
- External acoustic meatus (ear canal)
What is the pinna of the external ear formed from?
Avascular elastic cartilage
so nutrients are gained from the skin
What is the function of the pinna?
To collect soundwaves and funnel them into the external acoustic meatus
The lateral 1/3rd of the external acoustic meatus is formed by…
A. Cartilage
B. Bone
A. Cartilage
The medial 2/3rds are formed by bone (the petrous part of the temporal bone)
Which cells in the epithelial lining of the external acoustic meatus produce earwax?
Ceruminous glands
What structure marks the medial end of the external acoustic meatus?
The tympanic membrane
Which spinal nerves supply the majority of the pinna of the external ear?
C2 and C3
via the lesser occipital and greater auricular nerves
Which nerve supplies the superior external acoustic meatus and most of the tympanic membrane?
CN V3
via the auriculotemporal nerve
Which nerve supplies the inferior external acoustic meatus and part of the tympanic membrane?
CN X - the vagus nerve
When using an otoscope to look in the ear, what direction should you pull the pinna in…
-An adult
-A child
?
Adults: posterosuperiorly (as the EAM is curved)
Children: posteroinferiorly (as the EAM is short and straight)
Name the thin part of the tympanic membrane
Is it superior or posterior?
Pars flaccida
Superior
Name the thick part of the tympanic membrane
Is it superior or posterior?
Pars tensa
Posteroinferior
What is the function of the middle ear?
To conduct soundwaves from the external ear through the tympanic cavity and towards the inner ear
Name the auditory ossicles of the middle ear
Malleus
Incus
Stapes
The auditory ossicles decrease in size from lateral to medial. This helps to…
Amplify sound
What type of joint connects the auditory ossicles?
Synovial joints
malleoincal and stapeoincal
What does the footplate of stapes connect to?
The oval window of the optic capsule of the inner ear
The middle ear is found in the tympanic cavity. Name the 2 parts of the tympanic cavity
Epitympanic recess (superior to tympanic membrane)
Tympanic cavity proper
Which nerve delivers sensory information to the mucosa lining the tympanic cavity?
CN IX - the glossopharyngeal nerve
Name the 2 muscles of the tympanic cavity
Tensor tympani
Stapedius
Tensor tympani:
Which auditory ossicle does it insert onto?
What nerve innervates it?
- Malleus (runs from cartilaginous portion of eustachian tube to handle of malleus)
- CN V3 (mandibular division of trigeminal)
Stapedius:
Which auditory ossicle does it insert onto?
What nerve innervates it?
- Stapes (runs from the pyramidal eminence to the neck of stapes)
- CN VII (facial nerve)
What is the function of…
-Tensor tympani
- Stapedius
?
- Tensor tympani: dampens sound by reducing vibrations of the tympanic membrane (by pulling on the handle of malleus)
- Stapedius: dampens sound by reducing vibrations of stapes on the oval window
Describe the acoustic reflex in relation to the tensor tympani and stapedius muscles
Loud noises cause tensor tympani and stapedius to contract, which dampens the sound to protect the nerves from damage
What is the function of the Eustachian tube?
To equalise air pressure between the middle ear and nasopharynx
This is ideal for vibration of the auditory ossicles
The cartilaginous portion of the Eustachian tube is usually collapsed. Which muscles contract to open it?
The soft palate muscles
tensor veli palatini and levator veli palatini muscles
When would the Eustachian tube be opened?
When atmospheric pressure changes
e.g., increased atm. pressure under water, decreased atm. pressure at high altitidues
Increased atmospheric pressure (e.g., under water) pushes the tympanic membrane IN/OUT, resulting in reduced vibrations of the ossicles and muffled hearing
IN
Decreased atmospheric pressure (e.g., in a plane) pushes the tympanic membrane IN/OUT, resulting in reduced vibrations of the ossicles and muffled hearing
OUT
The posterior 1/3rd of the Eustachian tube is formed by…
A. Cartilage
B. Bone
B. Bone
The remainder is formed by cartilage
What is the torus tubarius?
The opening of the Eustachian tube in the nasopharynx
Why can tonsilitis/pharyngitis cause otitis media?
Bacteria/ viruses can spread from the nasopharynx, through the Eustachian tube, and into the middle ear