What is the anatomy of TMJ?

The temporomandibular joint is the joint which connects the mandibular condyle with the mandibular fossa of the temporal bone. The temporal bone is the bone at the side of the head, and the mandible is the lower jaw. This joint is vital for speech, chewing, and yawning. The articulation of this joint is controlled by muscles attached to and surrounding the jaw. An interposed articular disc separates the temporal bone and mandible from direct contact. To allow for lateral and rotational movement of the disc on the condyle, there are collateral ligaments which attach the disc to the condyle. Movement of the joint is lubricated by synovial fluid, which also transports nutrients and waste products to and from the articular surfaces. Nerves are responsible for coordinating voluntary and involuntary movements and sensations throughout the body. The trigeminal nerve provides sensory innervation for most of the head and face. Orofacial pain generally involves pain and dysfunction resulting from issues in the trigeminal nerve system. The 3 divisions of the trigeminal nerve system are the ophthalmic branch, maxillary branch, and mandibular branch. The ophthalmic branch transmits sensory information from the scalp and forehead, conjunctiva and cornea of the eye, upper eyelid, nose, nasal mucosa, the dura and blood vessels in the meninges, and frontal sinuses.

The maxillary branch controls the lower eyelid and cheek, nares and upper lip, palate and roof of the pharynx, maxillary, ethmoid, and sphenoid sinuses, and parts of the meninges. The maxillary branch is further divided into 3 branches (zygomatic, pterygopalatine (or sphenopalatine), and posterior superior alveolar). The anterior and greater
palatine nerves and the superior, middle, and anterior alveolar nerves innervate the soft palate, uvula, hard palate, maxillary gingiva and teeth, and mucous membranes of the cheek. The mandibular branch is responsible for sensory information from the lower lip, mandibular teeth and gingiva, floor of the mouth, anterior two-thirds of the tongue, and the chin. This branch is also responsible for most of the jaw and parts of the external ear and meninges. Most of the TMJ is innervated by the auriculotemporal nerve which branches off the mandibular branch of the trigeminal nerve. The mandibular branch is used by the motor nuclei to support the muscles of mastication. The skeletal muscles which facilitate movement of the temporomandibular joint muscles are commonly referred to as the muscles of mastication. Muscles of the head and neck also provide secondary support during chewing. The masticatory muscles include the masseter, medial pterygoid, and temporalis. These muscles are mainly responsible for elevating the mandible to close the mouth. For mandible depression (opening of the mouth), the digastric muscles are responsible. The inferior lateral pterygoid muscles are responsible for the protruding and lateral movements of the mandible. The superior lateral pterygoid muscles also provide stability for the condyle and disc.