Four different muscles connect to the lower jaw to facilitate its movement. These muscles are the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid. Each of these muscles occurs in pairs, with one of each muscle appearing on either side of the skull. The muscles work in combination to pivot the lower jaw up and down and to allow movement of the jaw from side to side.
Fractures to this bone may be minor or severe, with more severe fractures requiring the jaw to be wired shut to prevent movement during healing. Other injuries and infections that can affect the lower jaw include tendinitis, infections stemming from tooth decay or other tooth injuries, and temporomandibular joint disorder TMJD , which causes painful swelling where the mandible meets the cheekbone.
The supraspinatus muscle is a rotator cuff muscle located in the shoulder, specifically in the supraspinatus fossa, a concave depression in the rear…. The quadratus plantae is a muscle in the foot that extends from the anterior front of the calcaneus heel bone to the tendons of the digitorum….
The depressor labii inferioris muscle is a four-sided facial muscle located in the jaw area that draws the lower lip down and to the side.
The muscles of the face give it general form and contour, help you outwardly express your feelings, and enable you to chew your food. The quadriceps femoris is a group of muscles located in the front of the thigh. The Latin translation of 'quadriceps' is 'four headed,' as the group…. The palmaris brevis muscle lies just underneath the skin. It is a short muscle on the flat of the hand. The muscle begins at the flexor retinaculum in…. The movement of the upper arm and shoulder is controlled by a group of four muscles that make up the rotator cuff.
The largest and strongest muscle in…. The extensor pollicis longus muscle begins at the ulna and the interosseous membrane, a tough fibrous tissue that connects the ulna and the radius in…. List of Partners vendors. Also known as the lower jawbone, the mandible is the largest and strongest bone of the face. Tasked with holding the lower set of teeth in place, this bone has a symmetrical, horseshoe shape. Not directly connected to other bones of the skull, the mandible is the only moving bone of the skull and is attached to the major muscle groups of mastication chewing as well as the ligaments that make up the temporomandibular joint that allows motion.
Health issues that arise with this bone usually have to do with fracture or dislocation due to trauma. In addition, corrective surgeries may be performed on the mandible to correct misalignment due to improper development of the jaw. The largest facial bone, the mandible is roughly horseshoe-shaped, defining the lower margins and sides of the face. The body of the mandible is the almost rectangular front anterior portion of the bone, and it is grafted to the ramus wing-like portion on each side.
In adults, its external surface has a slight ridge at its midline called the mandibular symphysis, which divides and encloses a depression called the mental protuberance as it moves downward. The edges of this part rise up to make up the mental tubercle. To the side of this, and below the incisive front teeth is a depression called the incisive fossa, and there is an opening on each side adjacent to the premolars called the mental foramen.
The upper border, also known as the alveolar border, contains hollow spaces for the teeth. These bound the temporomandibular joint, which allows the bone to move. The lower surfaces of the ramus define the jawline, and the outer sides are connected to the masseter muscle for chewing. The inner surfaces contain several openings fossa that allow important nerves and arteries to access the mouth region.
Notably, the inferior alveolar nerve, a branch of the mandibular nerve , accesses the mandible foramen and runs frontward, providing sensation to the lower set of teeth. At the mental foramen, it branches into the incisive and mental nerves; the latter of these enervates the lower lip, whereas the former processes sensation for the mandibular premolar, canine, as well as lateral and central incisors.
Given that this bone is involved with mouth motions, many important muscle groups also make contact with the mandible. A number of muscles arise from this bone. Furthermore, other muscles link to the mandible, including:. Typically, men have more square-shaped mandibles than women, something which arises because their mental protuberances are larger, and they display a mandibular angle that is smaller. In rarer instances, however, the alveolar canal may be duplicated or even triplicated.
This is usually seen in X-ray and can complicate anesthesia practice in oral or facial surgery as there is a risk of accidentally piercing and damaging the nerves that populate these canals. Finally, cleft chin, which is basically an incomplete joining together of the bones of the mandible, can arise during embryonic development.
In these cases, there is a Y-shaped dimple in the middle of the chin. Along with the upper jaw or maxilla, the mandible serves an essential structural and protective function. The mandible is intimately involved with chewing function as well as most any movement of the mouth. The most commonly seen issue that arises in the mandible is fracture or dislocation due to an accident or fall.
These breaks are most commonly seen in the condyle portion of the bone, though they can arise in other portions, such as the body, the mandibular angle, and other parts of the ramus. Dislocations can also occur, with the most frequent of these being due to the mandible being pushed back. These can lead to an inability for the patient to close their mouth or a misalignment of the structure. Other problems, not necessarily related to trauma, may also arise in this part of the body.
Misalignment of the jaw—whether due to trauma or arising naturally—can seriously damage teeth and impact other parts of the head and neck. Furthermore, positioning of the mandible can be implicated in sleep apnea excessive snoring , cleft palate, and temporomandibular joint disorders pain right at the juncture of the upper and lower jaw.
A rarer, though no less significant condition is osteomyelitis , which is an infection of the bone. Treatment for mandible fracture depends on the location and scope of the issue. Following computerized tomography CT scan , X-ray , or magnetic resonance imaging MRI to assess the break, doctors typically have two choices: reduction or fixation. Reduction involves approximating the locations of the broken ends and setting the jaw to that position, often with wires wrapped around the teeth.
Fixation is similar in nature to reduction but includes the use of an additional arch bar that secures upper and lower teeth to one another for proper positioning.
Depending on the injury, soft tissues may also need to be pierced and used as additional support. Orthognathic surgery treats problems stemming from a misaligned jaw, as well as sleep apnea, cleft palate , and temporomandibular joint disorders. Those with micrognathia may require this type of surgery to correct alignment. After surgery, a significant amount of rehabilitation will be needed, with emphasis placed on ensuring proper positioning of the mandible with regards to the rest of the skull.
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