The human medial pterygoid muscle: Attachments and distribution of muscle spindles

Abstract

Introduction Published descriptions about the sites of origin of the human medial pterygoid muscle vary and there are few reports on the distribution and density of muscle spindles in this muscle. We aimed to: 1) determine the extent of anatomical variability in the origins and insertions of the superficial and deep heads of the human medial pterygoid muscle, and 2) determine the extent of variation in the distribution of spindles in the two heads of the muscle.

Materials and methods Thirty-nine human cadaver hemi-heads were dissected and the attachments of the medial pterygoid muscle examined. The whole muscle was removed, weighed, cut into segments and embedded in wax for light microscopy. Sections were stained with Weigert-Van Gieson stain and scanned into digital images. Spindles were manually counted.

Results In seven specimens, the deep head of the muscle arose from the medial surface of the lateral pterygoid plate and the pterygoid fossa. In 28 specimens, the origin extended onto the lateral surface of the medial pterygoid plate.

There were abundant muscle spindles in the middle of the muscle, slightly fewer 1cm toward the insertion, significantly fewer 1cm toward the origin, and few or no spindles near the origins of the superficial and deep heads or near their insertion.

Conclusion Firstly, this study shows that in 72% of the specimens examined, the origin of the medial pterygoid is wider than conventionally described in anatomical textbooks. Secondly, the segmental distribution of muscle spindles is described for the first time. This article is protected by copyright. All rights reserved.

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