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In anatomy, the masseter [help 1] is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. [5] The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.
The earliest signs may include: masseter muscle contracture following administration of succinylcholine, a rise in end-tidal carbon dioxide concentration (despite increased minute ventilation), unexplained tachycardia, and muscle rigidity. [5] Despite the name, elevation of body temperature is often a late sign, but may appear early in severe ...
Trismus is defined as painful restriction in opening the mouth due to a muscle spasm, [5] however it can also refer to limited mouth opening of any cause. [6] Another definition of trismus is simply a limitation of movement. [4]
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 ).
Myotonia congenita is a congenital neuromuscular channelopathy that affects skeletal muscles (muscles used for movement). It is a genetic disorder.The hallmark of the disease is the failure of initiated contraction to terminate, often referred to as delayed relaxation of the muscles and rigidity. [1]
In response, the masseter muscles will jerk the mandible upwards. Normally this reflex is absent or very slight. However, in individuals with upper motor neuron lesions the jaw jerk reflex can be quite pronounced. The jaw jerk reflex can be classified as a dynamic stretch reflex.
It passes laterally superior to the lateral pterygoid muscle, anterior to the temporomandibular joint, and posterior to the tendon of the temporalis muscle.It crosses (the posterior portion of) the mandibular notch alongside the masseteric artery before branching out upon the surface of the masseter muscle, then entering the muscle.
The first sign is trismus or lockjaw, then facial spasms (called risus sardonicus), followed by stiffness of the neck, difficulty in swallowing, and rigidity of pectoral and calf muscles. Other symptoms include elevated temperature, sweating, elevated blood pressure , and episodic rapid heart rate.