Temporomandibular Disorders Priorities for Research and Care (2020) / Chapter Skim
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Appendix D: Masticatory System: Anatomy and Function
Appendix D: Masticatory System: Anatomy and Function
Pages 403-410
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From page 403... ...
One additional bone, the sphenoid, is fixed between the upper jaw and the temporal bone. MASTICATORY MUSCLES The muscles associated with mandibular movement are organized into five groups according to their major functions.
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From page 404... ...
• Primary muscles of mastication: The most recognized group is composed of four muscles that function in pairs and are primarily responsible for TMJ function and mandibular movement. These in clude the masseter and temporalis muscles, which are responsible for closing the mandible; the medial pterygoid muscle, which is respon sible for closing and lateral movements of the mandible; and the lateral pterygoid muscle, which is responsible for opening, deviation to either side, and anterior movement of the jaw.
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From page 405... ...
A healthy masticatory system appears to function effortlessly; by contrast, a compromised system can produce pain and dysfunction. TEMPOROMANDIBULAR JOINTS TMJs include the rounded end of the mandible (mandibular condyle)
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From page 406... ...
Normal joint motion transitions seamlessly from rotation to translation to provide maximal mouth opening. In children, the primary growth center for the mandible lies immediately below the fibrocartilaginous lining, making it susceptible to damage from pathological conditions.
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From page 407... ...
Similarly, in response to information from the muscle spindles, a reflex activation of the closing muscles would occur during the rapid opening phase of chewing; the central pattern generator similarly actively suppresses the potential activation of the closing muscles. The presence of pain profoundly alters these internal controls; the muscle coordination decreases, and the reciprocal controls between the opening and closing muscles during the chewing cycles lose their effective ess, contributing to a degradation of function during both simple n movements of opening and closing and complex movements of chewing.
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From page 408... ...
The joint adjacent to the TMJ is the joint between the skull and the first cervical vertebrae, and controlled jaw function requires participation by much more than just the muscles that directly move the jaw. The group of accessory muscles that are indirectly associated with mandibular function attach to the sternum, temporal bone, clavicle, cervical vertebrae 1–7, and ribs 1–2.
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From page 409... ...
The stability of the TMJ is achieved via coordinated action of the muscles of mastication, some of which extend to the chest and to the shoulder. Consequently, healthy function in the TMJ is achieved through a complex layering of muscle activity.
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