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The mandible is a single, mobile, horseshoe-shaped bone that is part of the facial skeleton. It participates in the closing and opening movements of the mouth, it is necessary for grinding food and speaking. How is the mandible built? What are its functions?

The mandibleis primarily responsible for the mechanical work related to chewing food. It is where the teeth are anchored and participates in speaking. The mandible is connected to the skull with two temporomandibular joints.

Condylar processes together with the temporal bones form the temporomandibular joints. Initially, the mandible moves in a circular motion until the mouth is opened a little, about 2-3 cm wide, then there is a toboggan movement, while further opening the mouth, the mandible protrudes forward.

Jaw - anatomy

There are three parts in the mandible:

  • middle, i.e. shank
  • two lateral, i.e. branches (connecting to the ends of the stem)

The horseshoe-shaped shaft has two edges and two faces. The upper or alveolar rim of the mandible contains the sockets. Each alveolus is the location of a tooth that fits perfectly. The lower edge of the mandibular body is thicker, rounded and longer than the upper one. The mandibular body has an outer and an inner surface. Depending on the age of the person, the angle of the stem with the branch is 90-140 °.

On the front surface of the mandibular body, there are mental tumors and at the level of the first premolars - two mental openings through which the mental nerves and mental arteries emerge from the mandibular canal. The most protruding part of the shaft is the mental tuberosity. The lower jaw also has depressions which are places where various structures are located or attached. These are, among others, the sublingual pits - the sublingual glands and the bipartite pits, i.e. places for attachment of the abdomens of the anterior biplast muscles.

Jaw - anatomy

The main task of the mandible ismechanical workassociated with chewing food. That is why the mandible is made of a spongy substance located centrally, which is surrounded by a strong compact layer. The places where the lower jaw shows the highest hardness are the base of the lower jaw. The jaw surfaces are covered with the periosteum, vascularized and innervated. A compact creature, built of bone trabeculae forming the stroma, formsdistinctive layout. Bone trabeculae are arranged along the sieve lines, the so-called trajectories running from the chin side, then obliquely upwards, through the branch to the pointed process. The course of the sieve lines is usually parallel to the place of greatest pressure and stretching of the mandible during chewing.

The mandible also has places with reduced bone resistance, more prone to fractures or injuries. They occur in the area of ​​the canine, the angle of the mandible (near the seedling of the wisdom tooth) and around the neck of the articular process. Particularly durable places include the area located in the midline, reinforced with the mental symphysis and beardiness, and the area of ​​the mental opening, the perimeter of which is thickened with a dense bone border.

Muscles affecting the mandible

Grinding food with the lower jaw is done thanks to the muscles attached to the bones. Among 32 muscles (16 on each side) there are muscles that work in one direction, otherwise synergistic, and those that work in different directions - antagonistically.

  • lowering muscles- pulling the lower jaw downwards: inferior lateral pterygoid, biparticular, mandibiohyoid, hyoid-hyoid
  • lifting muscles- pulling the lower jaw up: masseter, medial pterygoid and temporal
  • receding muscles- pulling the lower jaw back: posterior temporal muscle fibers, medial feeder muscle fibers, biparticular, hyoid and mandiohyoid muscles
  • twisting muscles- pulling the lower jaw to the sides: unilaterally contracting inferior lateral pterygoid muscle and cooperating muscles, for example the mandibiohyoid muscle of the same side. The return movement can be performed with the medial and / or mandibiohyoid muscles of the opposite sides

Jaw - diseases

There are many disorders related to the masticatory organ. These include :

  • Dysfunction of the mandibular muscles

In the case of muscular dysfunctions, mental disorders are the most common. Patients, as a result of excessive stress, grind their teeth and clench them. This leads to muscle building, just like the muscles of other parts of the body through exercise. As a consequence, the teeth are clenched more and more. In such a case, it is recommended to visit a dentist who will suggest a treatment method that is optimal for the patient.

  • Blockage of the temporomandibular joint

When a joint is blocked, it cannot be moved. Most often this is when intervertebral disc(colloquially called a disc) in the temporomandibular joint will change its position and limit joint movements. The bones that make up the joint may also change position. Patients are often accompanied by pain. Movements in the joint are temporarily blocked. Sometimes its elements return spontaneously to their physiological position. If this is not the case, see a doctor.

  • Costen's syndrome or painful temporomandibular joint syndrome

In typical cases, the pain is initially limited to the temporomandibular joint and only occurs with chewing. Later, it can radiate to the temples, forehead, top of the head, and even the back of the head and neck. The pain is dull, but it may become more severe. It appears when you eat and talk for a long time. Patients complain of crackling in the joint, tension and pain in the masseter muscles, and limited chewing movements. There may be tinnitus or even hearing impairment

  • Szczękościsk

Trismus is associated with difficulty opening the mouth and making it impossible to speak. Trismus occurs in the course of:

  • hematomas: intra-articular, mandibular, sub-temporal and pterygo-palatal muscles, bone fractures, osteoarthritis
  • inflammation of the temporomandibular joint,
  • abscesses: auricle, external auditory canal, peritonsillar, parapharyngeal, periodontal, sub-temporal, oral floor
  • neoplasms: sub-temporal space, pterygo-palatine fossa, salivary glands and tissues surrounding the joint. The cause of trismus should be established before starting treatment. When this condition is prolonged, degenerative changes in the temporomandibular joints may occur.

  • Mechanical trauma of the lower jaw

The characteristic symptoms are pain when moving the lower jaw: talking or eating, and swelling of the face. You should see a doctor to assess whether a fracture has occurred and to plan treatment.

  • Jaw tumor

The mandibular tumor, with local malignancy, in most cases occurs in the area of ​​the molars in the back part of the mandible, and is rarely located in the maxilla. The tumor may recur and infiltrate the surrounding tissue, but it is very rarely metastatic. The enamel is rarely painful and is characterized by slow, long-term growth.

Malocclusion related to the lower jaw

  • Torso, or retrogeniais a malocclusion in which the mandible is retracted in relation to the maxilla, the front mandible growth is inhibited. Retracted lower jawis treated with braces and surgery.
  • Prodoguchiamay be a functional defect when the lower jaw is misaligned but properly constructed) or morphological, meaning excessive growth of the lower jaw. Like retrogeneity, it is treated with braces or surgery.

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Category:

Anatomy