![Definitions Related To Growth -
• The self multiplication of living substance [Huxley]
• Increase in size, change in proportion and progressive complexity
[Krogman]
• An increase in size [Todd]
• Entire series of sequential anatomic and physiologic changes
taking place from the beginning of pre natal life to senility [Meridith]
• Quantitative aspect of biologic development per unit of time
[Moyers]
• Change in any morphological parameter which is measurable
[Moss]
Development -
• Progress towards maturity [Todd]](https://image.slidesharecdn.com/growthdevelopment-generalprinciplesconcepts-200420195039/85/Growth-Development-General-Principles-Concepts-2-320.jpg)
Growth & Development - General Principles & Concepts
- 1. Growth And Development General Principles And Concepts PROF (Dr.) SAIBEL FARISHTA
- 2. Definitions Related To Growth - • The self multiplication of living substance [Huxley] • Increase in size, change in proportion and progressive complexity [Krogman] • An increase in size [Todd] • Entire series of sequential anatomic and physiologic changes taking place from the beginning of pre natal life to senility [Meridith] • Quantitative aspect of biologic development per unit of time [Moyers] • Change in any morphological parameter which is measurable [Moss] Development - • Progress towards maturity [Todd]
- 3. Factors affecting Physical Growth • Heredity • Nutrition • Illness • Race • Socio economic factors • Family size and Birth order • Secular Trends • Climatic and Seasonal Effects • Psychological Disturbances • Exercise
- 4. Some Concepts of Growth Concept of Normality - Normal refers to what is expected, is ordinarily seen or is typical. It should not be equated with that of the ideal. Normality changes with age, thus what is normall seen or is expected for one age group, may not be necessarily normal for a different age group. Rhythm of Growth - According to Hooton, human growth is not a steady and uniform process wherein all parts of the body enlarge at the same rate and the increments of one year are equal to that of the preceeding or succeeding year. However there seems to be a rhythm during the growth process. This is most clearly seen in body height.
- 5. The first wave of growth is seen in both males and females from birth to the 5th or 6th year. It is most intense and rapid during the first 2 years. The second accelerated growth period corresponding to adolescence is completed in girls between the 14th & 16th year, but extends in boys till 16th or 18th year. The third and final period of slow growth is seen between 18th & 20th years in females but goes on in boys untill 25th year.
- 6. Growth Spurts Growth does not take place uniformly at all times. There seems to periods when a sudden acceleration of growth occurs, which is termed as growth spurts. The physiological alteration in harmonal secretion is believed to be the cause for such accentuated growth. The timing of growth spurts differ in boys and girls. The following is the timing of the growth spurts - • Just before birth • One year after birth • Mixed dentition growth spurt Boys: 8-11 years Girls: 7-9 years • Pre pubertal growth spurt Boys: 14-16 years Girls: 11-13 years
- 7. Growth modification by means of functional and orthodontic appliances elicit better response during growth spurts. Surgical correction involving the maxilla and mandible should be carried out only after cessation of the growth spurts. Differential Growth Human body does not grow at the same rate throughout life. Different organs grow at different rates to a different amount and at different times. This is termed differential growth. Two important aspects to study differential growth are - • Scammon’s Curve of Growth • Cephalocaudal Gradient of Growth
- 8. Scammon’s Curve of Growth The body tissues can be broadly classified into 4 types. Lymphoid, Neural, General and Genital tissues. Each of these tissues grow at different times and rate.
- 9. Lymphoid tissue proliferates rapidly in late childhood and reaches almost 200% of adult size. This is an adaptation to protect children from infection, as they are more prone to them. By about 18 years of age, lymphoid tissue undergoes involution to reach adult size. Neural tissue grows very rapidly and almost reaches adult size by 6- 7 years of age. Very little growth of neural tissues occurs after 6-7 years. General or Visceral tissues consist of muscles, bones and other organs. They exhibit an S shaped curve with rapid growth upto 2-3 years of age, followed by a slow phase of growth between 3-10 years. After 10th year, a rapid phase of growth occurs terminating by 18th-20th year Genital tissues consists of the reproductive organs, They show negligible growth untill puberty. They grow rapidly towards puberty, reaching adult size after which growth ceases.
- 10. Cephalocaudal Gradient of Growth It simply means that there is an axis of increased growth extending from head towards the feet. Post natal growth of regions of the body that are away from the hypophysis is more. This growth concept can be illustrated as follows - • The head takes up about 50% of the total body length around the third month of intra-uterine life. At the time of birth, the trunk and the limbs have grown more than the head, thereby reducing the head to about 30% of body length. In the adult the size of the head is 12%. • The lower limbs are rudimentary around the 2nd month of intra uterine life. They later grow and represent 50% of the body length at adulthood. • At the time of birth, the cranium is proportionally larger than the face. Post natally the face grows more than the Cranium.
- 11. Methods of Gathering Growth Data • Longitudinal Studies • Cross Sectional Studies • Semi Longitudinal Studies Longitudinal Studies In this type of study, the observation and measurements pertaining to growth are made on a person or a group of persons at regular intervals over a prolonged period of time, therefore these are long term studies. Advantages – • As the same subjects are followed up over a long period, the specific developmental pattern of an individual can be studied and compared. • Variations in development among individuals within the sample can be studied.
- 12. Disadvantages – • As these are carried out over long periods of time, it takes years or decades to complete the study. • It requires maintenance of laboratory research personnel and data storage systems over long periods, which are expensive. • As these studies take a long time, there is a risk of the sample size reducing due to change of place etc. Cross-Sectional Studies These are carried out by observation and measurement made of different samples and studied at different periods. Advantages – • These studies are of short duration • Less expensive than Longitudanal studies • It is possible to get a large sample, as study is of shorter duration • It is possible to repeat the study in case of any flaw.
- 13. Semi Longitudinal Studies It has combined the cross-sectional and longitudinal methods, so as to derive the advantages of both the systems of gathering the growth data. Types Of Growth Data Opinion – is the crudest means of studying growth. It is a clever guess of an experienced person. This method is not very scientific and should be avoided when better methods are available. Observations – They are useful in studying all or none phenomena, such As presence or absence of Class II molar relation etc. Ratings and Rankings – Whenever quantification of a particular data is difficult, this method is used. Rating makes use of standard, conventionally accepted scales for classification. Ranking involves the arrangement of data in an orderly sequence based on the value.
- 14. Quantitative Measurements A scientific approach to study growth is one that is based on accurate measurements. The measurements can be of three types – • Direct Data: These are derived from measurements that are taken on living persons or cadavers by means of scales, measuring tapes and calipers. • Indirect Data: The growth measurements can also be had from images or reproduction of the person such as photographs, radiographs or dental casts. • Derived Data: This data is derived after comparing two measurements. These two sets of measurements can be of different time frames or of two different samples.
- 15. Methods of Studying Growth • Measurement Approaches – They comprise of measurement techniques that are carried out on living individuals. These methoda do not harm the animal. • Experimental Approaches – These are destructive techniques, where the animals are sacrificed. These are usually not carried out on humans. Bimetric Tests – These are the tests in which physical characteristics such as height, weight, skeletal maturation and ossification are measured and compared with standards. Vital Staining – This technique involves administration of certain dyes to the experimental animal, which gets incorperated in the bones. It is Then possible to study the manner in which bone is laid down, the site Of growth, the direction, duration and amount of growth at different Sites in the bone. The dyes used for this purpose are – Alizarin Red 5, Acid Alizarin Blue, Trypon Blue, Tetracycline, Lead Acetate.
- 16. Radioisotopes – When injected into tissue get incorporated in the developing bone and act as in vivo markers. These can later be detected By tracking down the radioactivity they emit. These include – Technetium 33, Calcium 45 and Potassium 32. Implants – It involves the implanting of small bits of biologically inert Alloys into growing bone. These serve as radiographic reference points For serial radiographic analysis. The metallic implants used for studying growth are very tiny, about 1.5 mm in length and 0.5 mm in diameter and are made of Tantalum metal. These implants are embedded in Certain areas of maxilla and mandible in order to study the growth of the skull. In Maxilla – The implants are placed in the hard palate behind the deciduous canines. Below the ANS. Two implants on either side of the Zygomatic process of maxilla. In the border between hard palate and alveolar process , medial to the first Molar. In Mandible – The implants are placed anterior aspect of symphysis, in The midline below the root tips. In the mandibular body and ramus region.
- 17. Radiographic Techniques – The most commonly used are Cephalometry And Hand wrist Radiographs. Cephalometry – It is a standardized radiographic technique of the cranio facial region. It was introduced by Broadbent in 1931. It has made possible to take serial radiographs of a patient’s skull in order to study the growth changes taking place. It is also a valuable aid in orthodontic diagnosis, treatment planning, evaluation of treatment results and for growth prediction. Hand Wrist x-rays – It is used to study the skeletal or biologic age of a person.The carpals have a definite schedule of appearance and ossification. Natural Markers – The histological features of a normal bone such as nutrient canals, lines of arrested growth and prominent trabeculae can be used as natural markers to study bone deposition, resorption and bone remodelling.
- 18. Mechanisms of Bone Growth Bone is a specialized tissue of mesodermal origin. It forms the structural framework of the body. Bone is a calcified tissue that supports the body And gives point of attachment to the musculature. Normal bone contains 32-36% of organic matter. Bone Deposition and Resorption – Bone changes in shape and size by two Basic mechanisms, bone deposition and bone resorption. This together is Called Bone Remodelling. The changes that bone deposition and resorption Can produce are – change in size, shape, proportion and relationship of the Bone with adjacent structures. Cortical Drift – A combination of bone deposition and resorption resulting In a growth movement towards the depositing surface is called Cortical Drift. If bone deposition and resorption are equal, then the bone thickness Remains constant. If in case more bone is deposited on one side and less Bone resorbed on the opposite side, then the thickness of the bone increases.
- 19. Displacement – It is the movement of the whole bone as a unit. It can be of two types – Primary and Secondary Displacement. Primary Displacement – If the bone gets displaced as a result of its own growth, it is called as Primary displacement. Secondary Displacement – If the bone gets displaced as a result of growth and enlargement of an adjacent bone, its called as Secondary displacement.
- 20. Osteogenesis The process of bone formation is called Osteogenesis. Bone formation takes place in two ways – Endochondral bone formation and Intra-membranous bone formation. Endochondral Bone Formation – In this type, the bone formation is preceded by formation of a cartilaginous model, which is subsequently replaced by bone. It occurs as follows – Mesenchymal cells become condensed at the site of bone formation. Some mesenchymal cells differentiate into chondroblasts and lay down hyaline cartilage. The cartilage is surrounded by a membrane called perichondrium which is highly vascular and contains osteogenic cells. The inter cellular substance surrounding the cartilage cells becomes calcified due to the influence of enzyme alkaline phosphatase. Thus, the nutrition to the cartilage cells is cut off leading to their death. This results in empty space formation called primary areolae. The blood vessels and osteogenic cells from the perichondrium invade the calcified cartilaginous matrix, leaving large empty spaces between the walls, called as Secondary areolae. The osteogenic cells from the perichondrium become osteoblasts and arrange themselves along the surface of these bars of calcified matrix.
- 21. The osteoblasts lay down osteoid which later becomes calcified to form a lamella of bone. This procedure is repeated again. Intra Membranous Bone Formation – in this type, the bone formation is not preceded by formation of a cartilaginous model. Instead bone is laid down directly in a fibrous membrane. This bone is formed in the following manner – At the site of bone formation, mesenchymal cells become aggregated. Some mesenchymal cells lay down bundles of collagen fiber. Some of these cells enlarge and acquire a basophilic cytoplasm and form osteoblasts. These osteoblasts secrete a gelatinous matrix called osteoid around the collagen fibres. They deposit calcium salts into the osteoid leading to conversion of osteoid into bone lamella. Now the osteoblasts move away from the lamellae and a new layer of osteoid is secreted which also gets calcified. Some of the osteoblasts get entrapped between two lamellaes, which are called osteocytes.
- 22. Theories of Growth Genetic Theory – This is one of the oldest theories. It states that all growth is controlled by genetic influence and is pre-planned. Sutural Theory – According to Sicher, paired parallel sutures that attach Facial areas to the skull and the cranial base region push the naso-maxillary complex forwards to pace it’s growth with that of the mandible. This theory also acknowledges the genetic influence of growth. Points against this theory – when an area of the suture is transplanted to another location, the tissue does not continue to grow. Also growth takes place in untreated cases of cleft palate, even in absence of sutures. Cartilagenous Theory – According to James Scott the intrinsic growth controlling factors are present in cartilage and periosteum, with sutures being only secondary. He viewed the cartilagenous sites throughout the skull as primary centres of growth. He also stated that the nasal septal cartilage is the pacemaker for growth of the entire naso-maxillary complex. Points in favour of this theory – in many bones, cartilage growth occurs, while bone merely replaces it. Epiphyseal plate and Nasal septal cartilage show innate growth potential.
- 23. The Functional Matrix Concept – The functional matrix hypothesis of Moss claims that the origin, form, position, growth and maintenance of all skeletal tissues and organs are always secondary. A number of relatively independent functions are carried out in cranio-facial region of the human body, like respiration, vision, hearing, balance, chewing, digestion, swallowing etc. Each of these functions is carried out by a Functional cranial component. Each of this component consists of all the tissues, organs, spaces and skeletal parts necessary to carry out a given function. It is divided into – Functional matrix and Skeletal unit. All the tissues, organs and functioning spaces as a whole comprise the Functional matrix, while the skeletal tissues related to this specific Functional Matrix comprise the skeletal unit. The Skeletal Unit – All skeletal tissues associated with a single function are called ‘the skeletal unit’. This may be comprised of bone, cartilage and tendinous tissue. When a bone is comprised of several contiguous skeletal units, they are termed as ‘micro skeletal units’. Example – maxilla and mandible. When adjoining portions of a number of neighbouring bones are united to function as a single cranial component, it is termed as ‘macro skeletal unit’.
- 24. The Functional Matrix – It consists of muscles, glands, nerves, vessels, fat, teeth and the functioning spaces. It is divided into – Periosteal matrix and Capsular matrix. The Periosteal Matrices – Act directly and actively upon their related skeletal units, thereby bringing about a transformation in their size and shape. This transformation is brought about by bone deposition and resorption. Capsular Matrices – Act indirectly and passively on their related skeletal units, producing a secondary compensatory translation in space. These alterations in spatial position is brought about by the expansion of the oro-facial capsule, within which the facial bones arise, grow and are maintained.The facial skeletal units are passively and secondarily moved in space as their enveloping capsule is expanded. This kind of growth is not brought about by bone deposition and resorption. The Neuro cranial capsule and the Oro facial capsule are examples of capsular matrices
- 25. Van Limborgh’s Theory – It is a multi factorial theory of 1970. Von Limborgh Explained the process of growth and development in a view that combines all the three existing theories. He supports the Functional matrix theory of Moss, Acknowledges some aspects of Sicher’s theory and does not rule out Genetic Involvement. He has suggested 5 factors that he believed controls growth - • Intrinsic Genetic Factors – Genetic control of the Skeletal units themselves. • Local Epigenetic Factors – Bone growth is determined by genetic control originating from adjacent structures like brain, eyes etc. • General Epigenetic Factors – Genetic factors determining growth from distant structures. Ex – sex harmone, growth harmone etc. • Local Environmental Factors – They are non-genetic factors from local external environment. Ex – habits, muscle force etc. • General Environment Factors – They are general non genetic influences. Ex – nutrition, oxygen etc.
- 26. Enlow’s Expanding ‘V’ Principle Many facial bones have a V shaped pattern of growth. The growth movements And enlargements of these bones occurs towards the wide ends of V as a Result of differential deposition and selective resorption of bone. Bone Deposition occurs on the inner side of the wide end of the V and bone resorption on the outer surface. Deposition also takes place at the ends of The 2 arms of V, resulting in growth movements towards the ends. The V pattern of growth occurs in a number of regions like base of mandible, ends of long bones, mandibular body, palate etc.
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