Question

The bony labyrinth is filled with
(A) Endolymph
(B) Synovial fluid
(C) Perilymph
(D) Humour

Answer 1

Hint: Bony labyrinth is the portion of the inner ear which is present within the petrous part of the temporal bone. Bony labyrinth is made up of bony spaces or cavities that enclose another portion of inner ear called membranous labyrinth.

Complete answer:
Ears are the organs that help in hearing and maintaining body equilibrium. Each ear is divided into three parts – outer ear, middle ear and inner ear.
Inner ear is further divided into two main parts – bony labyrinth and membranous labyrinth. Bony labyrinth is made up of three parts – vestibule, semicircular canals and cochlea. Membranous labyrinth is made up of four parts – saccule, urticle, semicircular ducts and cochlear duct. Bony labyrinth encloses membranous labyrinth.
Vestibule: Vestibule is the central portion of bony labyrinth. It encloses two parts of a membranous labyrinth known as saccule and utricle.
Semicircular canals: Bony labyrinth has three semicircular canals (anterior, lateral and posterior canals). These three canals are C shaped and perpendicular to each other. Semicircular canals have two ends, both of which open in vestibule. These canals enclose semicircular ducts.
Cochlea: Cochlea is a highly complex spiral canal of bony labyrinth. It encloses the cochlear duct.
All the three parts of bony labyrinth contain a fluid known as perilymph.
Endolymph is present in a membranous labyrinth. It is absent in bony labyrinths.
Synovial fluid is present in the spaces between synovial joints like shoulder joint, knee joint and saddle joint. Bony labyrinth does not contain synovial fluid.
Humour or humor was an old term used to describe the four types of body fluids – blood, black bile, yellow bile and phlegm. It was thought that these four fluids (humour) determine the physical and mental characteristics of a person.

So the correct answer is Option (C) Perilymph.

Note:
The bony labyrinth is internally lined by a tissue called periosteum. Periosteum gives rise to perilymph. Perilymph is similar in composition with CSF and other extracellular fluids but it contains less amount of protein. It is drained via perilymphatic ducts. The function of perilymph is to protect the inner membranous labyrinth from hard bony labyrinth.