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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 2 parts of lateral pterygoid have different actions. The lower head contracts during mouth opening, and the upper head contracts during mouth closing. The function of the lower head is to steady the articular disc as it moves back with the condyle into the articular fossa. It is relaxed during mouth closure. [27]
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 ...
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).
Oromandibular dystonia (OMD) is an uncommon focal neurological condition affecting the jaws, face, and mouth. [1] Oromandibular dystonia is characterized by involuntary spasms of the tongue, jaw, and mouth muscles that result in bruxism , or grinding of the teeth , and jaw closure.
It is a temporary condition that usually lasts no more than two weeks. Dental trismus is caused by an injury to the masticatory muscles, such as opening the jaw for an extended period of time or having a needle pass through a muscle. Typical dental anesthesia for the lower jaw involves inserting a needle into or through a muscle.
The temporalis muscle is covered by the temporal fascia, also known as the temporal aponeurosis. This fascia is commonly used in tympanoplasty, or surgical reconstruction of the eardrum. The temporalis muscle is accessible on the temples, and can be seen and felt contracting while the jaw is clenching and unclenching.
The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a bilaterally paired suprahyoid muscle located under the jaw.Its posterior belly is attached to the mastoid notch of temporal bone, and its anterior belly is attached to the digastric fossa of mandible; the two bellies are united by an intermediate tendon which is held in a loop that attaches to the hyoid bone.