The jaw is an important part of the facial skull. On the one hand, it has a great influence on a person’s appearance, and on the other hand, it is used for food intake and influences the way a person speaks.
What is the jaw?
The lower part of the head is called the jaw. It consists of the lower jaw, the upper jaw, and the temporomandibular joints. The upper jaw is firmly fused to the nasal bone and the zygomatic bone. The lower jaw is movably connected to the temporal bone by the temporomandibular joints. There is therefore only an indirect connection between the upper and lower jaws. Only the lower jaw is moved by the masticatory muscles. This principle structure is found in all mammals, in contrast to birds, in which the upper jaw is also movable.
Anatomy and structure
The maxillary bone and the palatine bone form the maxilla. It contains the maxillary sinus and forms the floor of the orbit. It also forms the floor and walls of the nasal cavity and, as part of the palate, the roof of the oral cavity. It has four processes:
- Frontal process – it connects the nasal bone, lacrimal bone and frontal bone.
- Zygomatic process – this triangular process is located below the orbital surface.
- Alveolar process – this arcuate process serves to accommodate the teeth.
- Palatal process – it forms a horizontal plate, which is located between the nasal surface and the alveolar process.
The maxilla and palate are traversed by nerves, different branches of the maxillary nerve. In an adult with healthy dentition sit in the upper jaw 16 teeth in tooth compartments, the alveoli. These sit in the alveolar process. The outer layer of the upper jaw bone is hard, its interior more spongy in structure. The lower jaw consists of a horseshoe-shaped jaw body, the front part of which forms the human chin. On both sides this jaw body has upward leading parts, the mandibular branches. The mandibular bone has three processes:
- Alveolar process – here, as in the upper jaw, the teeth are located.
- Articular process – it sits on the lower jaw branch and has a cylindrical articular head. This is the movable part of the temporomandibular joint.
- Muscle process – this is where the muscles of mastication attach.
The inferior alveolar nerve, also known as the mandibular dental nerve, which is a branch of the mandibular nerve, runs in a tunnel under the teeth of the lower jaw. In both the mandible and the maxilla, the teeth are located in tooth pockets called alveoli. However, they are not rigidly connected to these, but are suspended in the tooth pockets in a slightly movable manner by collagen fibers. The roots of the teeth are located in deep protrusions of the jaw bones.
Function and tasks
The jaw serves mainly for food intake. In this process, the teeth play an important role. The loss of teeth or their malposition have repercussions not only on the jaw, but also on other parts of the body. The misalignment of the teeth often leads to a malfunction of the temporomandibular joint. This then causes pain that can also radiate further into the head or the rest of the body. In addition, the jaw also affects the visual appearance of a person. It also affects pronunciation. In both cases, the teeth, as part of the jaw, are crucial. The temporomandibular joint serves to move the lower jaw. This movement is necessary for biting and chewing processes, but also for speech. Thus, the temporomandibular joint is one of the most stressed joints in the human body. Because this joint is located near the ear, pain originating from temporomandibular joint disorders is often misinterpreted as ear pain.
Diseases and ailments
Diseases and malformations of the jaw are divided into congenital and acquired disorders. A congenital malformation is, for example, the cleft lip and jaw or the cleft palate. These clefts develop during pregnancy. The individual parts of the face develop separately in early pregnancy and then grow together. If a disorder occurs during this growing together, the clefts develop. Jaw malpositions can also be congenital. The lower jaw is then displaced forward or backward. As a result, the two rows of teeth in the upper and lower jaws no longer fit together exactly.This is not only visually unsightly, it can also lead to problems when eating or speaking and affect the temporomandibular joint. An acquired disorder is temporomandibular joint arthrosis. It is an inflammation of the temporomandibular joint caused by wear and tear and can become very painful. It is caused either by age-related wear and tear of the bones or by misalignment of the teeth, which leads to increased bone wear. However, pain in the jaw can also be caused by inflammation of the ears. The head is crisscrossed by many nerve pathways that are interconnected. Thus, an inflammation in one area can quickly lead to a sensation of pain in another area. Jaw pain can also be caused by diseased teeth, especially inflamed tooth roots. Maxillary sinusitis is an inflammation of the mucous membrane in the maxillary sinus caused by viruses or bacteria. Acute maxillary sinusitis can result from a cold or runny nose. Bacteria enter through the nose and sinuses. It is contagious because the bacteria or viruses that cause it are spread by droplet infection. The chronic form of maxillary sinusitis usually results from an acute inflammation. It causes severe rhinitis symptoms and often headaches. Due to the proximity to the eye sockets, visual disturbances may also occur. The roots of the upper molars may also become inflamed.
