What is Phossy Jaw?

The lower jaw is the largest, strongest and lowest bone on the face. It forms the lower jaw and holds the lower teeth in place. The mandible is located below the maxilla. It is the only removable bone in the skull. ^[1]

The word "mandible" comes from the Latin " mandibula" , "jawbone" (literally "one for chewing"), like other joint tissues in the body, it is a midline connection, the bones are connected by fibrocartilage, Connections blend together in early childhood.

The mandible includes:

The body of the previous part--Body

Left and right branches-Ramus

Two main holes on the right and left side of the lower jaw

A branch of the alveolar nerve-the mandibular nerve ^[2]

Men usually have a more squared, stronger, and larger mandible than women. Mental processes are more pronounced in men, but can be visualized and palpated in women.

In rare cases, there may be bilateral inferior alveolar nerves. In this case, there is a second mandibular foramen, which is poorly located and can be detected by noting the double mandibular canals on the radiograph.

Over time, the mandible forms a bone (ossification), and the left and right cartilage are called Meckel cartilage.

These cartilages form the cartilage strips of the mandibular arch. Near the head, they are connected to the ear capsule, and they meet at the lower end of the mandibular union, which is the fusion point between the two bones and is organized by the mesoderm. They travel forward under the condyles and then bend downwards in a groove near the lower edge of the bone; in front of the canine teeth, they tilt up to the pubic symphysis. From the proximal end of each cartilage, the malleus and anvil bones, and the two bones of the middle ear are produced; as far as the tongue-shaped protrusion is concerned, the next subsequent part is replaced by fibrous tissue, which continues to form the sphenoid jaw ligament.

Between the tongue and canine teeth, the cartilage disappears, and its parts below and behind the incisors become ossified and merge with this part of the mandible.

With regard to the sixth week of fetal life, intra-membrane ossification occurred on the membrane covering the ventral outer surface of Meckel cartilage, and each half of the bone was formed by a single center that appeared near the foramen.

By the tenth week, Meckel's cartilage, located below and behind the incisors, was surrounded and invaded by dermal bone (also called the periosteum). Later, the accessory nucleus of cartilage appeared.

It forms the lower jaw and holds the lower teeth in place.

The mandible is jointed with the left and right temporal bones at the temporomandibular joint.

Condylar process, projecting from the upper (upper) and posterior branch of the bone, making the temporomandibular joint and the temporal bone

Coronoid process, projected from the upper and front of the ramus. This provides attachment to the temporal muscle

The teeth are located on the upper part of the mandible.

The frontmost part of the teeth is narrower and holds the front teeth.

The back maintains wider and flatter teeth and is mainly used to chew food. These teeth usually have wide and sometimes deep grooves on the surface

In leaf finfish and early fossil tetrapods, the bone that is homologous to the mammalian mandible is just the largest of several bones in the mandible. In such animals, it is called the dental bone or OS dentale, and forms the body of the outer surface of the claw. It consists of a number of splenial bones inlaid on the underside, while the angle of the claws is formed by angled bones and suprangular bones above it. The inner surface of the jawbone is lined up by the anterior bone of the joint, and the joint bone forms a joint with the skull. Finally, a set of three narrow coronary bones is located above the anterior bone of the joint. As the name suggests, most teeth are attached to the teeth, but the coronal bone usually also has teeth, sometimes in front of the joints.

However, this complex primitive pattern is simplified to varying degrees in most vertebrates because the bones are completely fused or disappeared. In teleost fish, only natural, articulated, and angled bones are left, while in living amphibians, this voluntary is accompanied only by anterior joints, and in tadpoles, one of which is coronal. The reptile's jaw has only one coronal protrusion and spleen, but retains all other primitive bones except anterior joints and periosteum.

Although in birds these different bones have fused into a single structure, in mammals most of the bones have disappeared, leaving behind the only remaining bone in the mandible-the mandible. As a result, the original jaw joint between the joint and the square bone has been lost and replaced by a brand new joint between the mandible and the temporal bone. The intermediate stage can be seen in some retractors, where there are two joint points. With the exception of volunteers, only a few primitive jaw bones remain in mammals; the anterior and square bones survive as hammer bones and anvil bones in the middle ear.

Finally, cartilage fish, such as sharks, do not have any bones in the jaws of other vertebrates. Instead, their jaws consist of cartilage structures that are homologous to other groups of Meckel cartilage. This is also an important element of the jaw of some primitive bone fish (such as catfish). ^[1]