Inner Ear Function and Structure Quiz

Study Notes

Transformations of energy in hearing: Acoustic energy is converted to mechanical energy, then hydraulic energy as it travels through the ear.
The inner ear amplifies sound; however, only a fraction (1/1000) of air’s acoustic energy efficiently transmits to inner ear fluids, resulting in approximately 30 dB hearing loss.
The tympanic membrane (eardrum) shows right or left orientation based on the cone of light: in the right ear, it is positioned at the 5 o’clock mark.

The umbo is the tip of the malleus located at the center of the tympanic membrane, which displays a small depression.
Parts of the tympanic membrane: superior section above anterior and posterior malleolar folds lacks a fibrous layer and connects to the bony ring (notch of Rivinus).
Anatomical divisions of the tympanic cavity include the epitympanum, mesotympanum, and hypotympanum.

Blood circulation to the ear is provided by branches of the external carotid artery, including middle meningeal, ascending pharyngeal, maxillary, and stylomastoid arteries.

The inner ear begins development in the 4th week of gestation when the ectoderm thickens beside the hindbrain, forming the otic placode.
The otic placode undergoes invagination, leading to the formation of the otic pit, which fuses to create the otic vesicle.

The pinna (auricle) leads to the external auditory canal, bordered by the temporalis muscle (superior), parotid gland (anterior/inferior), mastoids (posterior), and epitympanum (superomedial).
Functions include sound collection, localization (using interaural time and amplitude differences), and serving as an acoustic antenna, amplifying sounds in the 2-4 kHz range by 10-15 dB.

Adults have a longer and more angulated (45 degrees) eustachian tube compared to children's shorter and wider version, making otitis media more common in young children.
The eustachian tube’s lining consists of pseudostratified columnar epithelium with goblet cells.
Has two openings: nasopharyngeal (proximal, closes at rest and opens when talking, chewing, or yawning) and tympanic orifice.

Key roles include pressure equalization, mucociliary clearance and drainage, and protection of the middle ear.

The scala vestibuli begins at the oval window at the stapes footplate, spirals to the apex of the cochlea, and communicates with scala tympani via the helicotrema.