HIS Ear Anatomy & Physiology 2 — Questions and Answers
Question 1: Which structure connects the middle ear to the nasopharynx and helps equalize pressure?
- Eustachian tube (Correct answer)
- External auditory meatus
- Semicircular canal
- Round window
Correct answer: Eustachian tube
The Eustachian tube (auditory tube) connects the middle ear cavity to the nasopharynx, allowing pressure equalization on both sides of the tympanic membrane.
Question 2: The oval window is a membrane-covered opening that connects which two structures?
- Middle ear to inner ear (Correct answer)
- Outer ear to middle ear
- Cochlea to vestibule
- Semicircular canals to cochlea
Correct answer: Middle ear to inner ear
The oval window is a membrane-covered opening in the bony wall separating the middle ear from the inner ear, where the stapes footplate transmits vibrations.
Question 3: Which type of hair cells in the cochlea are primarily responsible for active amplification of sound?
- Outer hair cells (Correct answer)
- Inner hair cells
- Pillar cells
- Deiters' cells
Correct answer: Outer hair cells
Outer hair cells (OHCs) are electromotile and provide active mechanical amplification of basilar membrane motion, boosting sensitivity by up to 40–60 dB.
Question 4: What is the primary function of the round window in the cochlea?
- To allow fluid pressure to dissipate after oval window displacement (Correct answer)
- To support the tectorial membrane
- To separate the scala media from the scala tympani
- To house the spiral ganglion neurons
Correct answer: To allow fluid pressure to dissipate after oval window displacement
The round window membrane flexes outward when the oval window is pushed inward, allowing incompressible cochlear fluid to move and basilar membrane displacement to occur.
Question 5: Reissner's membrane separates which two compartments of the cochlea?
- Scala vestibuli from scala media (Correct answer)
- Scala media from scala tympani
- Scala tympani from scala vestibuli
- Helicotrema from scala vestibuli
Correct answer: Scala vestibuli from scala media
Reissner's membrane forms the upper wall of the scala media (cochlear duct), separating it from the perilymph-filled scala vestibuli above.
Question 6: The endolymph found in the scala media is unusual because it has a high concentration of which ion?
- Potassium (K+) (Correct answer)
- Sodium (Na+)
- Calcium (Ca2+)
- Chloride (Cl-)
Correct answer: Potassium (K+)
Unlike most extracellular fluids, endolymph has a very high potassium ion concentration (~150 mM), which is essential for generating the endocochlear potential.
Question 7: Which cranial nerve transmits auditory information from the cochlea to the brainstem?
- CN VIII (vestibulocochlear nerve) (Correct answer)
- CN VII (facial nerve)
- CN V (trigeminal nerve)
- CN IX (glossopharyngeal nerve)
Correct answer: CN VIII (vestibulocochlear nerve)
The cochlear branch of cranial nerve VIII (vestibulocochlear nerve) carries afferent signals from the spiral ganglion neurons to the cochlear nuclei in the brainstem.
HIS Ear Anatomy & Physiology 2
Which structure connects the middle ear to the nasopharynx and helps equalize pressure?