title: Observational study on the occurrence of muscle spindles in human digastric and mylohyoideus muscles.
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 (P < 0.001) 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.
authors.affiliation: Dipartimento di Medicina Sperimentale, Sezione di Anatomia Umana, Università degli Studi Genova, 16132 Genova, Italy.
authors.forename: Daniele
authors.identifier: 0000-0002-1623-1116
authors.initials: D
authors.lastname: Saverino
authors.affiliation: Dipartimento di Medicina Sperimentale, Sezione di Istologia, Università degli Studi Genova, 16132 Genova, Italy.
authors.forename: Amleto
authors.initials: A
authors.lastname: De Santanna
authors.affiliation: Dipartimento di Medicina Sperimentale, Sezione di Anatomia Umana, Università degli Studi Genova, 16132 Genova, Italy ; The Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, NY 11030, USA.
authors.forename: Rita
authors.identifier: 0000-0002-0174-6133
authors.initials: R
authors.lastname: Simone
authors.affiliation: Dipartimento di Medicina Sperimentale, Sezione di Istologia, Università degli Studi Genova, 16132 Genova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cervioni
authors.affiliation: Afdeling Experimentele Anatomie, Vrije Universiteit Brussel, 1050 Brussels, Belgium.
authors.forename: Erik
authors.identifier: 0000-0003-4325-9576
authors.initials: E
authors.lastname: Cattrysse
authors.affiliation: Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno Infantili, Campus Universitario di Savona, Università degli Studi Genova, 17100 Savona, Italy.
authors.forename: Marco
authors.identifier: 0000-0001-8643-7200
authors.initials: M
authors.lastname: Testa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D008875:Middle Aged; D009470:Muscle Spindles / Q000502:physiology*