ears

• external ear has the auricle or pinna which collects sound and looks like a shell with elevations and depressions
• external acoustic meatus conducts sound and runs from the concha to the tympanic membrane, is S shaped and slightly tortuous.
• the lateral 3rd of the auricle is cartilaginous while the medial 2/3rd is bony
• ceruminous glands are modified sweat glands that secrete cerumen
• the tympanic membrane is a thin, elliptical, semi transparent fibrous sheet
• the 3 auditory ossicles are the malleus (hammer shaped), incus (anvil shaped), and stapes (stirrup shaped)
• the middle ear has the tympanic cavity
• the roof of the middle ear has the tegmen tympani which is a thin plate of bone that's part of the petrous part of the temporal bone
• the floor of the middle ear has a thin bony plate or fibrous tissue that separates the tympanic cavity from superior bulb of the internal jugular vein
• the anterior wall of the middle ear has thin sheet of bone that separates the internal carotid artery

  
  

  the anterior wall has 2 openings, the lower that's larger for the auditory or eustachian tube, and the upper that's smaller for the canal of the tensor tympani muscles
• the posterior wall of the middle ear has an upper part that has an irregular opening for the aditus to the mastoid antrum. below it is a small conical projection called the pyramid and its apex is attached to the tendon of the stapedius muscle
• the lateral wall of the middle ear is the tympanic membrane
• the tensor tympani originates from the auditory tube wall and inserts to the handle of the malleus

  its nerve supply is the mandibular division of the trigeminal nerve

  it dampens down vibrations of the tympanic membrane
• the stapedius originates from the bony projection on the posterior wall called the pyramid and inserts into the neck of the stapes

  its nerve supply is the facial nerve

  it dampens down vibrations of the stapes
• the internal ear has a bony labyrinth
• the internal ear has the vestibule which is the central pillar that lies posterior to the cochlea and anterior to the semicircular canals
• the lateral wall of the internal ear has the fenestra vestibuli which is closed by the base of the stapes
• the fenestra cochlea is closed by the secondary tympanic membrane
• the internal ear has the semicircular canal which is located posterior, anterior, and lateral, it opens into the posterior part of the vestibule
• the internal ear has the cochlea which resembles a snail shell
• the fenestra vestibuli is where the stapes is attached to the oval window
• the cochlea is where the sounds are converted into signals that are sent to the brain
• the vestibulocochlear nerve and the facial nerve will enter the inner ear through the internal acoustic meatus