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Growth and Development

Dr.Omar S.M.J.Ali
PhD Orthodontic

Growth and Development

Growth : increase in size or number
Development : an increasing degree of organization

Growth is largely an anatomic phenomenon,

whereas development is physiologic and behavior

Growth

increase in size

1 cm3

8 cm3


Development
Change in the ratio

1 cm3

1 cm3

Human G & D

1 cm3

8 cm3

GROWTH
DEVELOPMENT

• Growth may or may not bring development

• E.g.: A child may growth fat but becoming fat no functional improvement may take place



• Development is possible without growth.
• E.g.: A person may not gain height, weight or size but can functional improvement in other aspects.

In fetal life,

at about the third month of intrauterine development,
the head takes up almost 50 % of the total body length
In contrast, the limbs are still rudimentary and the trunk is underdevelope

By the time of birth,

the trunk and limbs have grown faster than the head and face, so that the proportion of the entire body devoted to the head has decreased to about 30%.



Changes in proportions of the head and face during growth At birth, the face and jaws are relatively underdeveloped compared with their extent in the adult. As a result there is much more growth of facial than cranial structures postnatally

Teeth are unique: no change or growth after eruption.

The Nature of Skeletal Growth

At the cellular level, there are only three possibilities for growth;
• Hypertroph: an increase in the size of individual cells
• Hyperplasia: increase in the number of the cells
• Secretion of extracellular material : contributing to an increase in size independent of the number or size of the cells themselves

HYPERPLASIA

proliferating cells
(cell division)
HYPERTROPHY
Increase in cell size
secretion
Extracellular matrix


Hypertroph
Hyperplasia
Secrete extracellular material
Occur in
Skeletal
growth

Growth and Development

Hyperplasia is a prominent feature of all forms of growth
Hypertrophy occurs in a number of special circumstances but is a less important mechanism than hyperplasia in most instances
Although tissues throughout the body secrete extracellular material, this phenomenon is particularly important in the growth of the skeletal system, where extracellular material later mineralizes.

Growth and Development

The fact that the extracellular material of the skeleton becomes mineralized leads to an important distinction between growth of the soft or non mineralized tissues of the body and the hard or calcified tissues.

Interstitial growth

HYPERPLASIA
proliferating cells
(cell division)
HYPERTROPHY
Increase in cell size
secretion
Extracellular matrix
If the extracellular matrix is NOT mineralized,
interstitial growth may continue in soft tissues and cartilages.


Growth and Development
Hard tissues are bones, teeth, and sometimes cartilages. Soft tissues are everything else. In most instances ,cartilage, particularly the cartilage significantly involved in growth, behaves like soft tissue and should be thought of in that group, rather than as hard tissue.

Growth and Development

Growth of soft tissues occurs by a combination of hyperplasia and hypertrophy.
These processes go on everywhere within the tissues, and the result is what is called interstitial growth, which simply means that it occurs at all points within the tissue.
• Interstitial growth

Secretion of extracellular material can also

accompany interstitial growth, but hyperplasia primarily and hypertrophy secondarily are its characteristics
Growth and Development
• Interstitial growth

Interstitial growth is a prominent aspect of overall skeletal growth because a major portion of the skeletal system is originally modeled in cartilage. This includes the basal part of the skull as well as the trunk and Iimbs.
Growth and Development
• Interstitial growth




Development and maturation of the chondrocranium (cartilage: light blue, bone: stippled dark blue)
A , Diagrammatic representationa t about 8 weeks
B. , Skeletal development at 12 weeks.
Growth and Development

Growth

Development
Hypertroph
Hyperplasia
extracellular material
Interstitial growth