The skeletal muscles are mostly made up of muscles with skeletal fixation. Skeletal muscles, including their neuromuscular components, are essentially involved in every movement of the body and are part of the striated muscle. Among the skeletal muscles include the masticatory muscles.
This part of the skeletal muscle is composed of four different muscles that attach to the mandible and participate in the chewing. One of these four muscles is the masseter muscle, which is formed during embryonic development along with the other masticatory muscles from the connective tissue parts of the first gill arch. The muscle is involved in the so-called masseter reflex. This is a self-reflex of the masticatory muscles, preceded by a blow to the lower jaw. The masseter reflex is one of the innate protective reflexes of the human jaw. Basically, all mammals have a masseter muscle. The exact anatomy of the muscle differs from one species to another.
In humans, the masseter muscle originates at the zygomatic arch. For other mammals, the skeletal muscle often originates from the crista facialis on the upper jaw. The human masset muscle is a feathered muscle that consists macroscopically of a superficial and a deep portion.
The superficial portion slants diagonally in the direction of the dorsal-caudal, reaching the ramus mandibulae and tuberositas masseterica. The deep part of the muscle runs caudally in the vertical and thus extends to the Ramus mandibulae. The muscle is innervated by the nervus massetericus, a branch of the mandibular nerve. In addition to the arteria masseterica, the arteria transversa faciei is responsible for the supply of blood to the muscle. About the skeletal muscle pulls in humans a parotid gland duct. The masseter muscle, like the other three masticatory muscles, is highly displaceable. Dense fascia envelopes the masticatory muscles for this purpose.
The masseter muscle, together with the muscles of the temporal and medial pterygoid muscles, close the jaw. Thus, the muscle allows on the one hand the actual jaw closure and on the other hand the sideways movement and longitudinal movement of the lower jaw. The movements of the muscle are in Kauakt involved in the crushing of the food and thus ensure proportionate food intake. In addition, the Muculus masseter triggers a chain reaction that is just as important for food intake.
The movements of the muscle massage the glandula parotis as part of the chewing process. The gland is the paired parotid gland, whose job is the production of saliva. The stimulation of the gland causes saliva to be secreted. As a result of the chewing movements, the produced saliva reaches solitary single glands in the pharyngeal and oral mucosa via the ducts. In this way, the masseter muscle stimulates the chewing food with saliva by stimulating the parotid gland. The salivary enzymes initiate the digestion process of sugar molecules such as starch and cleave proteins by means of proteases.
The porridge produced by the chewing motion is thus prepared for digestion in the stomach. In addition, the enforcement of the porridge with saliva facilitates the swallowing process. Apart from these tasks, the Muculus Masseter fulfills protective functions for the jaw as part of the masseter reflex. The reflex movement corresponds to a muscle stretching reflex and is one of the protective reflexes of the jaw. When the skeletal muscle is stretched by a blow on the lower jaw, the masseter reflex causes contraction of the muscle, just like any other muscle stretching reflex. The jaw closes with the loop connection of afferent and efferent neurons.
Specifically, the masseter reflex is part of the neurological reflex examination. The examiner examines by means of light strokes on the lower jaw whether the congenital masseter reflex has been preserved in the patient. Anomalous reflex responses may imply paralysis of the trigeminal nerve. Lesions of the trigeminal nerve trigger peripheral paralysis, such as occurs in the context of polyneuropathy.
This disease is usually based on causes such as malnutrition, poisoning, infections or trauma. Central nerve lesions may also be indicated by an altered masseter reflex, especially those in the brainstem area. In such a case, tumors, strokes and inflammatory processes are the cause. In addition to neuromuscular palsies, the masseter muscle may gain pathological relevance in the context of painful symptoms. Pain within the masticatory muscles is about three times as common as TMJ pain. These myofascial pains can radiate over the entire neck and back area and are often the result of missing bites and repeated mauling of the masticatory muscles.
Under certain conditions, the masseter muscle may become painfully inflamed. Such inflammations can be the result of a bacterial infection. Much more common, however, in the context of muscle overloads or missing bites to an inflammation of the skeletal muscle. In addition to these phenomena, pathological phenomena such as the jaw lock are associated with the masticatory muscles. The cause of a jaw lock is a spasm of the masticatory muscles.
Tension also sometimes affects the masseter muscle. Such tensions are noticeable especially during the chewing in the form of pain in the jaw. Less common than these phenomena is the atrophy of the masseter muscle. In this phenomenon, the masticatory muscle gradually degrades due to contexts such as immobilization.Tags: