耳石器の機能と病態

The otolith organs: its normal and pathological physiology

I．耳石器の機能

　1．耳石器の構造と機能の関係

　ヒトを念め哺乳動物には側頭骨の骨迷路内に，ほぼ似た形の膜迷路がある。膜迷路は蝸牛，耳石器と半規管の3部分に分かれ内耳を形成している（図1）。

　蝸牛は音を，耳石器は頭部の位置や頭部に加わる直線加速度を，半規管は頭部に加わる回転加速度を検知し，有毛細胞，支持細胞，神経終末のほか物理的刺激を有毛細胞に有効に伝達する装置を有し，機械的刺激受容器mechanoreceptorとして似た構造となっている。

　The inner ear, or the labyrinth, can be separated to the auditory and the vestibular part. The three semicircular canals, the utricle and the saccule belong to the vestibular labyrinth, which are acting mostly as reflex organs to keep the body equilibrium by responding to the head movements or the head positions.

　The canals have the haircell-cupula-endolymphatic system and they are sensitive to rotatory accelerations to the head.

Both the utricle and the saccule have the otolith membranes, which are consited of jelly-like substance with fine crystals of calcium carbonate.