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1. Synchondrosis
 The cartilaginous neurocranium consists of
several cartilages that fuse and undergo
endochondral ossification to give rise to the base
of the skull. The cartilaginous junction between
two bones are called synchondrosis.
A synchondrosis is a cartilaginous joint where
hyaline cartilage divides and subsequently
converted into bone. (Bishara)
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2. Synchondrosis are left over from primary
cartilages of the early cartilaginous basicranium
after the endochondral ossification centre
appear during the fetal development. (Enlow)
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3. Suture
 They are fibrous joints comprised of sheets of
dense connective tissue that separate bones of
the calvaria. They are present during fetal and
early neonatal time. (Bishara)
 The periosteum has different names in different
sites. When the periosteum of the one bone
meets with the periosteum of other bone, it is
called as suture. (Moyers)
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4. Growth site
 It was believed that craniofacial sutures
generated tissue-separating force during growth,
thereby pushing apart the various bones of the
craniofacial complex. At this point in time, there
is an overwhelming and convincing body of
research evidence to support the view that
sutures are adaptive and compensatory growth
mechanism these are the growth sites.
(Bishara)
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5.  Some depository fields grow much more rapidly
or to a much greater extent than others. The
same is true for the resorptive field. Fields that
have some special significance role in the growth
process are often called as the growth sites.
(Enlow)
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6. Growth centre
 The concept of a growth centre evolved from
the observation of long bone growth. The
epiphyseal plates of long bone were noted for
their ability to grow under conditions of
mechanical loading. Among the craniofacial
theorist, a growth center came to mean a center
with the ability to generate tissue separating
forces.
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7. The condyle and some other special sites are
sometimes named as growth centers. This has
come into disfavor , however because it is now
believed that such centers do not actually
control the growth process of the bone as a
whole. They are not master centers that directly
regulate the overall growth process of the entire
bone and all its regional parts. (Enlow)
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8. Intramembraneous bone formation
Intramembraneous bone is derived from neural crest
cells. This occurs in five steps
 Osteoblasts produce osteoid tissue- Osteoblasts
differentiate from the ectomesenchymal condensation
center and produce a fibrous bone matrix.
 Cells an blood vessels are encased- as osteoid
deposition by osteoblasts continues, cells are encased
and become osteocytes. Blood vessels are retained
within the spaces and eventually become surrounded
by bone and a haversian system starts to form to
nourish the bone. www.indiandentalacademy.com

9.  Osteoid tissue is produce by membrane cells-
Osteocytes loose there capacity to contribute directly
to an increase in bone size, but the osteoblasts in the
surface periosteum produce more osteoid tissue
thereby layers to the surface of the existing bone.
 Osteoid calcifies- Bone matrix eventually becomes
mineralized and makes bone relatively impermeable to
the nutrients and metabolic wastes.
 Essential membrane covers the bone- an out side
bone membrane called periosteum and an inside
membrane called the endosteum are essential for the
bone survival
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10. Endochondral bone formation
 This occurs in five steps: -
 Hypertrophy of chondrocytes and matrix calcifies-
With in the cartilage primodium matrix a center of
calcification appears. Chondrocytes show
hypertrophic changes, and calcification of the cartilage
matrix continues.
 Invasion of blood vessels and connective tissue cells-
Blood vessel invade from the perichondrium into the
calcifying matrix , bringing undifferentiated
connective tissue cells.
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11.  Osteoblasts differentiate and produce osteoid tissue-
From the connective tissue precursor cells, osteoblasts
differentiate and deposit osteoid on the remnants of
the calcified cartilage matrix.
 Osteoid tissue calcifies- The fibrous bone matrix
mineralizes.
 Membrane covers the bone
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12. Primary Secondary
 The chondroblasts synthesis
intercellur matrix.
 The cartilaginous matrix
seen to isolate the dividing
chondroblasts from local
factors able to restrain or
stimulate the cartilage
growth rate.
 The pre chondroblasts are
not surrounded by
cartilaginous matrix, when
secondary chondroblasts
begin synthesizing the
cartilaginous matrix they
usually stop dividing.
 The dividing cells are not
surrounded by cartilaginous
matrix and thus not isolated
from the influence of local
factors.
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