Abstract
The development of the human mandible is proceeded
by the formation of Meckel's Cartilage within the
substance of the mandibular arch. This hyaline
cartilaginous rod is in relationship dorsally with
the primordium of the malleus. It commences
development in 12 m.m. stage is chondrified cornpletely
at the 30 m.m. stage and the two sides unite together'
at the symphysis.
The primary and only centre of ossification of
the mandible is present in the 17 m.m. stage. It is
situated within the fork formed by the incisive and
mental branches of the inferior dental nerve, when
first formed it lies as a delicate lamella of membrane
bone vertically placed on the lateral aspect of
Meckel's Cartilage.
From this centre a lamella of membrane bone
develops which extends from the region of the symphysis
to that of the dorsal tip of Condyloid process,
recognized in 37 m.m. stage. The inner alveolar
wall is formed as an ingrowth of bone from this
original lamella lying on the lateral aspect of
Meckel's Cartilage.
The flattened and expanded ventral extremity of
Meckel's Cartilages are invaded by bone at two points
in the 44 m.m. stage, this process of endochrondral
ossification is by direct extension from the adjacent
membrane bone. By further ossification the whole of
that portion of Meckel's Cartilage lying ventral to
the mental foramina is incorporated within the sub-
stance of the mandible. That part of Meckel's
Cartilage lying dorsal to the mental foramen is not
ossified, it atrophies and disappears, it is not
enclosed or incorporated within the bone of the mandible.
At the 44 m.m. stage a strip of hyaline
cartilage develops on the superior edge condyloid
process it persists for some time and is later ossified
from the adjacent bone.
At 82 m.m. stage an additional strip of hyaline
cartilage develops along the anterior border of the
coronoid process. This Cartilage is also ossified
directly from the adjacent bone.
At the 95 m.m. stage islands of cartilage in the
appearance of nodules and strips are seen close to the
symphysis mostly on the inner, lower and superior
aspects of the internal alveolar wall. These are
regarded as the hypertrophied remnants of the ventrally
expanded portion of Meckel's Cartilage. They are
later ossified directly from the adjacent bone. The
human mandible is a compound bone each half of which
has developed from a single centre of ossification.
All the morphological characteristics of the
adult bone is presented in definitive form by the
mandible from a 200 m.m. human foetus.
