1 The scala tympani and vestibuli both contain endolymphperi

1. The scala tympani and vestibuli both contain _______________(endolymph/perilymph) whereas the scala media contains ___________(endolymph/perilymph).

2. Which of the following extrinsic eye muscles is/ are innervated by CN III? (check all that apply)

A. inferior oblique

B. inferior rectus

C. lateral rectus

D. medial rectus

E. superior oblique

F. superior rectus

Solution

1. The scala tympani and vestibuli both contain perilymph whereas the scala media contains endolymph.

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Perilymph and endolymph are the two types of fluids found in the cochlear canals.

Perilymph: Its ionic composition is similar to extracellular fluid which is found elsewhere in the body and this perilymph fills the scalae tympani and vestibuli.

Endolymph: It is found inside the cochlear duct (scala media). This endolymph composition is unique and is not found elsewhere in the body.

2. Which of the following extrinsic eye muscles is/ are innervated by CN III? (check all that apply)

A. inferior oblique

B. inferior rectus

D. medial rectus

F. superior rectus

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The above four extrinsic muscles are seen to be innervated by the Oculomotor Nerve (CNIII). Abducens nerve (CNVI) will innervate the lateral rectus and Trochlear Nerve (CNVI) is seen innervating the superior oblique muscles