解剖学と生理学: 現在の研究
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概要

The Ilio-Coccygeus Muscle (ICM) Does it have an Enabling Role in Urination?

Bernard Guerquin*

An analysis of the literature has allowed for a redefinition of the anatomy of the ilio-coccygeus muscle (ICM) its insertions and its trajectory, the direction of its fibers and its relation to the base of the bladder. Static MRI studies have revealed its V-shaped appearance, while dynamic MRI has been used to visualize its concave contraction into a dome-shape that provides support to the levator plate, raising the base of the bladder. Histological studies have shown that the percentage of type I muscle fibers is 66% to 69%, which is comparable to the type I fiber content of the pubovisceral muscle (PVM), thus reflecting both its postural role as well as functions based on frequent voluntary contractions. Together, these data suggest an active role for the ICM which, upon urination, allows for voluntary hardening of the levator plate. The abdominal pressure from bearing down hence enables urinary draining by compressing the bladder on a hard surface. The physiological function of the ICM is therefore not only postural, but also to enable urination. From a therapeutic perspective, a multicentric study has shown that, by reinforcing the action of the ICM, use of a Diveen intrauterine device improved dysuria.