All Topics  
Ossification of the mandible

 

 
   Email Print
   Bookmark   Link
 

 

Ossification of the mandible
 
 
  Topics Ossification of the mandible Topic Home

The mandible
Mandible

The mandible or inferior maxillary bone forms the lower jaw and holds the lower tooth in place. It also refers to both the upper and lower sections of the beaks of birds....
 is ossified in the fibrous membrane covering the outer surfaces of Meckel's cartilages.

These cartilages form the cartilaginous bar of the mandibular arch (see p.






Discussion
Ask a question about 'Ossification of the mandible'
Start a new discussion about 'Ossification of the mandible'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Gray178
Gray179
Gray180
Gray181
The mandible
Mandible

The mandible or inferior maxillary bone forms the lower jaw and holds the lower tooth in place. It also refers to both the upper and lower sections of the beaks of birds....
 is ossified in the fibrous membrane covering the outer surfaces of Meckel's cartilages.

These cartilages form the cartilaginous bar of the mandibular arch (see p. 66), and are two in number, a right and a left.

Their proximal or cranial ends are connected with the ear capsules, and their distal extremities are joined to one another at the symphysis
Symphysis

A symphysis is a cartilage fusion between two bones. It is a type of cartilaginous joint.Unlike synchondroses, symphyses are permanent....
 by mesodermal tissue.

They run forward immediately below the condyles and then, bending downward, lie in a groove near the lower border of the bone; in front of the canine tooth
Canine tooth

In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed tooth....
 they incline upward to the symphysis
Symphysis

A symphysis is a cartilage fusion between two bones. It is a type of cartilaginous joint.Unlike synchondroses, symphyses are permanent....
.

From the proximal end of each cartilage the malleus
Malleus

The malleus or hammer is a hammer-shaped small bone or ossicles of the middle ear which connects with the incus and is attached to the inner surface of the eardrum....
 and incus
Incus

The incus or anvil is the anvil-shaped small bone or ossicles in themiddle ear. It connects the malleus to the stapes. It was first described by Alessandro Achillin of Bologna....
, two of the bones of the middle ear, are developed; the next succeeding portion, as far as the lingula, is replaced by fibrous tissue, which persists to form the sphenomandibular ligament
Sphenomandibular ligament

The sphenomandibular ligament is a flat, thin band which is attached above to the spina angularis of the sphenoid bone, and, becoming broader as it descends, is fixed to the Lingula of mandible of the mandibular foramen....
.

Between the lingula and the canine tooth the cartilage disappears, while the portion of it below and behind the incisor teeth becomes ossified and incorporated with this part of the mandible.

Ossification takes place in the membrane covering the outer surface of the ventral end of Meckel's cartilage (Figs. 178 to 181), and each half of the bone is formed from a single center which appears, near the mental foramen, about the sixth week of fetal life.

By the tenth week the portion of Meckel's cartilage which lies below and behind the incisor teeth is surrounded and invaded by the membrane bone.

Somewhat later, accessory nuclei of cartilage make their appearance:
  • a wedge-shaped nucleus in the condyloid process
    Condyloid process

    The condyloid process is part of the mandible and is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck....
     and extending downward through the ramus;
  • a small strip along the anterior border of the coronoid process
    Coronoid process

    The Coronoid process can refer to:* The coronoid process of the mandible, part of the ramus mandibulae of the mandible* The coronoid process of the ulna...
    ;
  • smaller nuclei in the front part of both alveolar walls and along the front of the lower border of the bone.


These accessory nuclei possess no separate ossific centers, but are invaded by the surrounding membrane bone and undergo absorption.

The inner alveolar border, usually described as arising from a separate ossific center (splenial center), is formed in the human mandible by an ingrowth from the main mass of the bone.

At birth the bone consists of two parts, united by a fibrous symphysis, in which ossification takes place during the first year.

The foregoing description of the ossification of the mandible is based on the researches of Low 44 and Fawcett, 45 and differs somewhat from that usually given.