Abstract
<p>Voluntary perioral movements, including speech articulation, deliberate lip posturing, and postural stabilization during oral closure, require motor precision despite the absence of muscle spindles and proprioceptive receptors in perioral musculature. The facial nerve is purely efferent, providing no direct sensory return. How the motor system achieves stable control under these constraints has remained unresolved. We propose the Orofacial Region as Integrated System (ORIS) model as a mechanistic candidate tailored to voluntary and automatic segmental perioral behaviors. The model identifies cutaneous mechanoreception via the trigeminal nerve as the primary afferent channel for perioral motor stabilization and proposes that the controlled variable is the spatial equilibrium of dermal surface tension across the perioral sheet, monitored by slowly and fast-adapting mechanoreceptors concentrated in the perioral region. The orbicularis oris sphincter provides circumferential tensile stability against which directional muscles act, with the modiolus anguli oris serving as the primary force-transmission junction. Three testable predictions follow from this architecture. Clinical implications for facial motor rehabilitation are discussed.</p>