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The four classical muscles of mastication elevate the mandible (closing the jaw) and move it forward/backward and laterally, facilitating biting and chewing. Other muscles are responsible for opening the jaw, namely the geniohyoid , mylohyoid , and digastric muscles (the lateral pterygoid may play a role).
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.
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 mylohyoid muscle elevates the hyoid bone and the tongue. This is particularly important during swallowing and speaking. Alternatively, if other muscles are used to keep the position of the hyoid bone fixed, then the mylohyoid muscle depresses the mandible. [1] It also functions as reinforcing the floor of mouth. [1]
B. X-ray, MRI or bone scintigraphy demonstrate TMJ disorder; C. Evidence that pain can be attributed to the TMJ disorder, based on at least one of the following: pain is precipitated by jaw movements or chewing of hard or tough food; reduced range of or irregular jaw opening; noise from one or both TMJs during jaw movements
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles.
The upper joint compartment formed by the articular disc and the temporal bone is involved in translational movement—this is the secondary gliding motion of the jaw as it is opened widely. [ 2 ] In some cases of anterior disc displacement, the pain felt during movement of the mandible is due to the condyle compressing this area against the ...
It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor muscle . The pectoralis major arises from parts of the clavicle and sternum , costal cartilages of the true ribs , and the aponeurosis of the abdominal external oblique muscle ; it inserts onto the lateral lip of the ...