Search results
Results from the WOW.Com Content Network
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.
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 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 facial muscles are a group of striated skeletal muscles supplied by the facial nerve (cranial nerve VII) that, among other things, control facial expression. These muscles are also called mimetic muscles. They are only found in mammals, although they derive from neural crest cells found in all vertebrates.
Inverse Marcus Gunn phenomenon is a rare condition [5] that causes the eyelid to fall upon opening of the mouth. In this case, trigeminal innervation to the pterygoid muscles of the jaw is associated with an inhibition of the branch of the oculomotor nerve to the levator palpebrae superioris, as opposed to stimulation in Marcus Gunn jaw-winking.
The mandibular nerve (V 3) carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw (except the angle of the jaw, which is supplied by C2-C3), parts of the external ear and parts of the meninges. The mandibular nerve carries touch-position and pain-temperature sensations from the mouth.
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 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.