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BioMed Research International
Volume 2014 (2014), Article ID 294263, 6 pages
http://dx.doi.org/10.1155/2014/294263
Research Article

Observational Study on the Occurrence of Muscle Spindles in Human Digastric and Mylohyoideus Muscles

1Dipartimento di Medicina Sperimentale, Sezione di Anatomia Umana, Università degli Studi Genova, 16132 Genova, Italy
2Dipartimento di Medicina Sperimentale, Sezione di Istologia, Università degli Studi Genova, 16132 Genova, Italy
3The Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, NY 11030, USA
4Afdeling Experimentele Anatomie, Vrije Universiteit Brussel, 1050 Brussels, Belgium
5Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno Infantili, Campus Universitario di Savona, Università degli Studi Genova, 17100 Savona, Italy

Received 3 February 2014; Revised 3 July 2014; Accepted 7 July 2014; Published 16 July 2014

Academic Editor: Tales A. Aversi-Ferreira

Copyright © 2014 Daniele Saverino et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Although the occurrence of muscle spindles (MS) is quite high in most skeletal muscles of humans, few MS, or even absence, have been reported in digastric and mylohyoideus muscles. Even if this condition is generally accepted and quoted in many papers and books, observational studies are scarce and based on histological sections of a low number of specimens. The aim of the present study is to confirm previous data, assessing MS number in a sample of digastric and mylohyoideus muscles. We investigated 11 digastric and 6 mylohyoideus muscles from 13 donors. Muscle samples were embedded in paraffin wax, cross-sectioned in a rostrocaudal direction, and stained using haematoxylin-eosin. A mean of 5.1 ± 1.1 (range 3–7) MS was found in digastric muscles and mean of 0.5 ± 0.8 (range 0–2) in mylohyoideus muscles. A significant difference ( ) was found with the control sample, confirming the correctness of the histological procedure. Our results support general belief that the absolute number of spindles is sparse in digastric and mylohyoideus muscles. External forces, such as food resistance during chewing or gravity, do not counteract jaw-opening muscles. It is conceivable that this condition gives them a limited proprioceptive importance and a reduced need for having specific receptors as MS.