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Elevation and depression are movements above and below the horizontal. The words derive from the Latin terms with similar meanings. [c] Elevation is movement in a superior direction. [19] For example, shrugging is an example of elevation of the scapula. [20] Depression is movement in an inferior direction, the opposite of elevation. [21]
Emotional stress (anxiety, depression, anger) may increase pain by causing autonomic, visceral and skeletal activity and by reduced inhibition via the descending pathways of the limbic system. The interactions of these biological systems have been described as a vicious "anxiety-pain-tension" cycle which is thought to be frequently involved in TMD.
The anterior and posterior belly of the digastric are also involved in the depression of the mandible and elevation of the hyoid bone and are therefore relevant to the masticatory system. [2] Ligaments. There are various ligaments associated with the TMJ and these limit and restrict border movements by acting as passive restraining devices.
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 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.
When a jaw is malrotated around the transverse facial axis, it is said to have abnormal pitch. When malrotated around the anteroposterior axis, the jaw has an abnormal roll, a condition also known as cant. Finally, when a jaw is malrotated around the vertical axis, it has abnormal yaw. It can occur in maxilla and/or mandible and could result ...
This can lead to easy subluxation of the joint and trismus (lock jaw). [5] Deformation of the mandibular fossa, often part of temporomandibular dysplasia , causes similar problems in dogs . [ 6 ] [ 7 ] This may resolve spontaneously, or require surgery .
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 ).