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During jaw movements, only the mandible moves. Normal movements of the mandible during function, such as mastication, or chewing, are known as excursions. There are two lateral excursions (left and right) and the forward excursion, known as protrusion. The reversal of protrusion is retrusion.
It is the condyles within the fossa and the associated muscles and ligaments together with its neuromuscular link that determines mandibular movements. Lateral, protrusive and repressive excursions of the mandible are guided by the posterior system. Lateral excursions. It is important to define the movement of the condyles in lateral excursions:
A concerted effort of the lateral pterygoid muscles helps in lowering the mandible and opening the jaw. Unilateral action of a lateral pterygoid muscle causes contralateral excursion (a form of mastication), usually performed in concert with the medial pterygoids. [citation needed] When they work independently, they can move the mandible side ...
Temporomandibular joint dysfunction (TMD, TMJD) is an umbrella term covering pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skull).
In humans, the mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint. This is an extremely complex joint which permits movement in all planes. The muscles of mastication originate on the skull and insert into the mandible, thereby allowing for jaw movements during contraction.
The medial pterygoid muscle has functions including elevating the mandible (closing the mouth), protruding the mandible, mastication (especially for when the maxillary teeth and the mandibular teeth are close together), [1] and excursing the mandible (contralateral excursion occurs with unilateral contraction).
Posselt's envelope of motion or Posselt's envelope of movement refers to the range of motion of the lower jaw bone, or mandible. This envelope was first described by Ulf Posselt in 1952. It is a diagrammatic representation of a sagittal view of maximum mandibular movement.
The jaw jerk reflex or the masseter reflex is a stretch reflex used to test the status of a patient's trigeminal nerve (cranial nerve V) and to help distinguish an upper cervical cord compression from lesions that are above the foramen magnum.