dr. richa khanna human growth encompasses physical, mental, psychological, social and moral...

CRANIOFACIAL GROWTH AND DEVELOPMENT :

POSTNATAL (part 1)

Dr. Richa Khanna

INTRODUCTION

Human growth encompasses physical, mental, psychological, social and moral development.

We shall deal here mostly with the postnatal physical growth in human beings in the craniofacial region.

Postnatal growth takes place from birth to 20 years of age.

INTRODUCTION

Growth and development, though closely related, are not synonymous.

Growth usually refers to an increase in size or number but tends to be linked more to change than anything else.

Occasionally, however, the increase will be in neither size nor number, but in complexity.

Definitions related to GrowthJ.S.

Huxley“The self multiplication of living substance.”

Krogman “Increase in size, change in proportion and progressive complexity.”

Todd “An increase in size.”

Meridith- “Entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility.

Moyers “Quantitative aspect of biologic development per unit of time.”

Moss Change in any morphological parameter which is measurable

profit Growth refers to an increase in size/number

INTRODUCTION

Development connotes an increasing degree of organization, often with unfortunate consequences for the natural environment. the term development is used to refer to an increase in complexity.

One price of increased development is a loss of potential

Todd “Development,” according to Todd, “is progress towards maturity”.

Profit Development is in complexity

Moyers According to Moyers, development refers to all the naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death.

INTRODUCTION

CHARACTERISTICS OF GROWTH AND DEVELOPMENT

PATTERN In studies of growth and development, the concept

of pattern is an important one. Pattern in growth represents proportionality.

It refers not just to a set of proportional relationships at a point in time, but to the change in these proportional relationships over time

Eg: "cephalocaudal gradient of growth." This simply means that there is an axis of increased growth extending from the head toward the feet


Cephalocaudal Gradient of Growth: In fetal life, at about the third month of intrauterine

development, the head takes up almost 50% of the total body length.

At this stage, the cranium is large relative to the face and represents more than half the total head.

In contrast, the limbs are still rudimentary and the trunk is underdeveloped.

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%.

The overall pattern of growth thereafter follows this course, with a progressive reduction of the relative size of the head to about 12% of the adult.


PATTERNAnother aspect of the normal growth pattern isthat not all the tissue systems of the body growat the same rate

Scammon’s curve of growth- Richard Scammon.

Lymphoid tissues attain a 200% growth by the age of ten and then regress afterwards.

Neural tissue attains full growth by the age of six and then stops.

General tissues follow a sigmoid growth pattern.

Genital tissue grow significantly only at puberty and achieve full growth at about 20 yrs of age.


PATTERNPatterns repeat, whether in the

organization of different-colored tiles in the design of a floor or in skeletal proportions changing over time


VARIABILITYA second important concept in the study of

growth and development is variability.

Rather than categorizing people as normal or abnormal, it is more useful to think in terms of deviations from the usual pattern and to express variability quantitatively.

One way to do this is to evaluate a given child relative to peers on a standard growth chart


An individual who stood exactly at the midpoint of the normal distribution would fall along the 50% line of the graph.

One who was larger than 90% of the population would plot above the 90% line;

one who was smaller than 90% of the population would plot below the 10% line.

TIMINGA final major concept in physical

growth and development is that of timing.

Variation in timing arises because the same event happens for different individuals at different times. Eg: growth spurts.


Growth Spurt : Periods when a sudden acceleration of

growth occurs. Physiological alteration in hormonal

secretion cause for Growth Spurts


TIMINGS OF GROWTH SPURTS.a. Just before birth b. One year after birthc. Mixed dentition growth spurtBoys : 8-11 yearsGirls : 7-9 yearsd. Pre-Pubertal growth spurtBoys : 14 - 16 yearsGirls : 11-13 years


GENETIC INFLUENCES ON GROWTHwhole family of transforming growth factor-

beta genes now is known to be important in regulating cell growth and organ development

It is likely that in the future, genetic screening of blood or other tissue samples will be used to identify patients with orthodontic problems who are likely to respond well or poorly to specific treatment modalities


NATURE OF SKELETAL GROWTHAt the cellular level, there are only three

possibilities for growth. The first is an increase in the size of individual

cells, which is referred to as hypertrophy. The second possibility is an increase in the

number of the cells, which is called hyperplasia. The third is for the cells to secrete extracellular

material, thus contributing to an increase in size independent of the number or size of the cells themselves.


Hyperplasia is a prominent feature of all forms of growth.

Hypertrophy occurs in a number of special circumstances but is a less important mechanism

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.


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

Hard tissues are bones, teeth, and sometimes cartilages.

Soft tissues are everything else


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

Secretion of extracellular material can also accompany

interstitial growth, but hyperplasia primarily and hypertrophy secondarily are its characteristics.

Interstitial growth is characteristic of nearly all soft tissues and of uncalcified cartilage within the skeletal system.


In contrast, when mineralization takes place so that hard tissue is formed, interstitial growth becomes impossible.

Hyperplasia, hypertrophy, and secretion of extracellular material all are still possible, but in mineralized tissues, these processes can occur only on the surface, not within the mineralized mass.

This process is called direct or surface apposition of bone


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 limbs.


At third month of intrauterine life a continuous plate of cartilage extends from the nasal capsule posteriorly all the way to the foramen magnum at the base of the skull. Cartilage is a nearly avascular tissue whose internal cells are supplied by diffusion through the outer layers. This means, of course, that the cartilage must be thin. At early stages in development, the extremely small size of the embryo makes a chondroskeleton feasible, but with further growth, such an arrangement is no longer possible without an internal blood supply.

During the fourth month in utero, there is an ingrowth of blood vascular elements into various points of the chondrocranium (and the other parts of the early cartilaginous skeleton). These areas become centers of ossification, at which cartilage is transformed into bone, and islands of bone appear in the sea of surrounding cartilage . The cartilage continues to grow rapidly but is replaced by bone with equal rapidity. The result is that the amount of bone increases rapidly and the relative (but not the absolute) amount of cartilage decreases. Eventually, the old chondrocranium is represented only by small areas of cartilage interposed between large sections of bone, which assume the characteristic form of the ethmoid, sphenoid, and basioccipital bones. Growth at these cartilaginous connections between the skeletal bones is similar to growth in the limbs.

This is called endochondral bone formation

In the long bones of the extremities, areas of ossification appear in the center of the bones and at the ends, ultimately producing a central shaft called the diaphysis and a bony cap on each end called the epiphysis.

Between the epiphysis and diaphysis is a remaining area of uncalcified cartilage called the epiphyseal plate(growth plate). The epiphyseal plate cartilage of the long bones is a major center for their growth, and in fact, this cartilage is responsible for almost all growth in length of these bones.

Toward the end of the normal growth period, the rate of maturation exceeds the rate of proliferation, the last of the cartilage is replaced by bone, and the epiphyseal plate disappears. At that point, the growth of the bone is complete, except for surface changes in thickness, which can be produced by the periosteum.

Not all bones of the adult skeleton were represented in the embryonic cartilaginous model, and it is possible for bone to form by secretion of bone matrix directly within connective tissues, without any intermediate formation of cartilage.

Bone formation of this type is called Intramembranous Bone Formation. This type of ossification occurs in the cranial vault and both jaws

ENDOCHONDRAL BONE

INTRAMEMBRANOUS BONE

Changes in the Shape and Position of Bone

Any change in bone morphology or spatial relationship can be accomplished by one of two processes:

Remodeling : Remodeling is the selective bone apposition by osteoblasts and resorption by osteoclasts


Translation : a) As a result of bone remodeling and

changes in its shape and size, the bone itself will change its position in space. This phenomenon is called primary translation

b) Secondary translation, on the other hand, occurs when the growth of one bone results in a change in the spatial position of an adjacent bone

TRANSLATION A. Changes occurring within bone "x" cause the bone to change its position in space.B. Changes occurring in bone "x" result in the translation or displacement of bone "y."

dr. richa khanna human growth encompasses physical, mental, psychological, social and moral...

Documents

postnatal growth

craniofacial growth

postnatal physical growth

overall pattern of growth

feet characteristics

axis of increased growth

normal growth pattern

moral development