Anatomical basis of lingual hydrostatic deformation

Abstract

SUMMARY The mammalian tongue is believed to fall into a class of organs known as muscular hydrostats, organs for which muscle contraction both generates and provides the skeletal support for motion. We propose that the myoarchitecture of the tongue, consisting of intricate arrays of muscular fibers, forms the structural basis for hydrostatic deformation. Owing to the fact that maximal diffusion of the ubiquitous water molecule occurs orthogonal to the short axis of most fiber-type cells, diffusion-weighted magnetic resonance imaging (MRI)measurements can be used to derive information regarding 3-D fiber orientation in situ. Image data obtained in this manner suggest that the tongue consists of a complex juxtaposition of muscle fibers oriented in orthogonal arrays, which provide the basis for multidirectional contraction and isovolemic deformation. From a mechanical perspective, the lingual tissue may be considered as set of continuous coupled units of compression and expansion from which 3-D strain maps may be derived. Such functional data demonstrate that during physiological movements, such as protrusion, bending and swallowing, hydrostatic deformation occurs via synergistic contractions of orthogonally aligned intrinsic and extrinsic fibers. Lingual deformation can thus be represented in terms of models demonstrating that synergistic contraction of fibers at orthogonal or near-orthogonal directions to each other is a necessary condition for volume-conserving deformation. Evidence is provided in support of the supposition that hydrostatic deformation is based on the contraction of orthogonally aligned intramural fibers functioning as a mechanical continuum.

Tongue and Lateral Upper Airway Movement with Mandibular Advancement

“…This study showed evidence of the tongue acting as a muscular hydrostat. 17,36 The area of the tongue grid in the sagittal plane was not different pre and post mandibular advancement. In a muscular hydrostat, the shape changes but the volume remains constant.…”

Effect of Sleeping Position on Upper Airway Patency in Obstructive Sleep Apnea Is Determined by the Pharyngeal Structure Causing Collapse

“…Thus an alternative mechanism is needed for these patients. The muscular hydrostat argument 17,18 may provide insight into this phenomenon, whereby the tongue maintains a constant volume (regardless of the forces acting on it ie, gravity, muscle activation). In this case, our data lead us to speculate that an enlarged tongue (thereby posteriorly located) has little space to move into (with position changes/muscle activation) regardless of whether supine or lateral.…”

The diversity of hydrostatic skeletons

“…In mammalian tongues, the intrinsic musculature typically includes transverse muscle fibers in alternating sheets of parallel muscle fibers oriented more or less vertically and horizontally and longitudinal muscle fibers in bundles around the central core of transverse muscle fibers. Mammalian tongue deformations and many types of tongue movement are generated according to the general principles outlined above for muscular hydrostats (Bailey and Fregosi, 2004;Gilbert et al, 2007;Kier and Smith, 1985;McClung and Goldberg, 2000;Napadow et al, 1999). Muscular-hydrostatic mechanisms may also be important in the support and movement of many lizard tongues and some frog tongues (Chiel et al, 1992;Nishikawa et al, 1999;Smith and Mackay, 1990;Smith, 1986;van Leeuwen, 1997;van Leeuwen et al, 2000;Wainwright and Bennett, 1992a;Wainwright and Bennett, 1992b).…”