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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 lateral pterygoid muscle (or external pterygoid muscle) is a muscle of mastication. It has two heads. It lies superior to the medial pterygoid muscle. It is supplied by pterygoid branches of the maxillary artery, and the lateral pterygoid nerve (from the mandibular nerve, CN V 3). It depresses and protrudes the mandible. When each muscle ...
There are no precise histological boundaries because the modiolus is an irregular zone where dense, compact, interlacing tissue grades into the stems of individually recognizable muscles. It is contributed to by at least nine muscles: orbicularis oris , buccinator , levator anguli oris , depressor anguli oris , zygomaticus major , zygomaticus ...
The facial muscles are just under the skin (subcutaneous) muscles that control facial expression. They generally originate from the surface of the skull bone (rarely the fascia), and insert on the skin of the face. When they contract, the skin moves. These muscles also cause wrinkles at right angles to the muscles’ action line. [2]
The jaw elevator muscles develop the main forces used in mastication. The force generated during routine mastication of food such as carrots or meat is about 70 to 150 newtons (16 to 34 lbf ). The maximum masticatory force in some people may reach up to 500 to 700 newtons (110 to 160 lbf ).
The superficial branches run beneath the skin and above the superficial muscles of the face, which they supply: some are distributed to the procerus, joining at the medial angle of the orbit with the infratrochlear and nasociliary branches of the ophthalmic.
The researchers looked at the temporalis muscles, which are related to the jaw, on MRI images. Participants were then grouped into categories based on their muscle size.
The orbicularis oris is not a simple sphincter muscle like the orbicularis oculi; it consists of numerous strata of muscular fibers surrounding the orifice of the mouth, but having different direction. It consists partly of fibers derived from the other facial muscles which are inserted into the lips, and partly of fibers proper to the lips.