Growth and Development Notes PDF

GROWTH AND DEVELOPMENT Outline Notes GROWTH - Normal changes in amount of living substance - Emphasizes the normal dimensional changes during development - Change in quantity DIFFERENTIATION - Change from the generalized cells or tissues to...

GROWTH AND DEVELOPMENT Outline Notes GROWTH - Normal changes in amount of living substance - Emphasizes the normal dimensional changes during development - Change in quantity DIFFERENTIATION - Change from the generalized cells or tissues to more specialized kinds during development - Change in quality or kind TRANSLOCATION - Change in position 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. - Growth + Differentiation + Translocation MATURATION - Qualitative changes which occur with aging TYPES OF GROWTH DATA 1. Opinion – not based on quantitative data 2. Observation – useful for studying all-or-none phenomena 3. Ratings (comparison with conventional accepted scales) and Rankings (array data in ordered sequences according to value) 4. Quantitative measurements a. Direct data b. Indirect data c. Derived data METHODS OF GATHERING DATA 1. Longitudinal – measurement made of the same person or group at regular intervals through time 2. Cross-sectional – measurement made of different individuals or different samples and studied at different periods 3. Overlapping or semilongitudinal data – combined BASIC TENETS OF GROWTH 1. Pattern - This indicates the proportionality of the given object in relation to its various sizes, including the changes in this proportionality over a period of time. a. Cephalocaudal gradient of growth: There is an axis of increased growth extending from the head toward the feet.  b. Differential growth: Not all the tissue systems of the body grow at the same rate. 2. Variability - It indicates the degree of difference between two growing individuals in all four planes of space including time. 3. Timing - Largely under genetic control, yet altered by the environment. All the individuals do not grow at the same time. Eg. variation in timing of menarche (onset of menstruation) in girls. a. Growth Spurts: periods of sudden rapid increases Name of Spurt Female Male Infantile/childhood growth spurt 3 years old 3 years old Mixed dentition/Juvenile 6-7 years old 7-9 years old Prepubertal/Adolescent 11-12 years old 14-15 years old Factors affecting physical growth - Genetic endowment - Environmental factors - Functional forces GROWTH FIELDS: Outer and inner surfaces of bone, covered by soft tissues, cartilage or osteogenic membranes, have areas known as growth fields. These fields spread all along the bone in a mosaic pattern, and are responsible for producing an alteration in the growing bone. GROWTH SITES: These are growth fields that have a special significance in the growth of a particular bone, e.g. mandibular condyle in the mandible, maxillary tuberosity in the maxilla. GROWTH CENTERS: These are special growth sites, which control the overall growth of the bone, e.g. epiphyseal plates of long bones. GROWTH MOVEMENT Cortical drift - Towards the depository surface. Combination of resorption and deposition. Displacement - Movement of bone as a unit; can be Primary & Secondary displacement. OSSIFICATION Intramembranous - Transformation of mesenchymal connective tissue, usually in membranous sheets, into osseous tissues. Endochondral - Conversion of hyaline cartilage prototype models into bone. ✓ Hypertrophy ✓ Hyperplasia ✓ Extracellular material = INTERSTITIAL GROWTH – end result; occurring at all points within the tissue THEORIES OF SKULL GROWTH CONTROL 1. Genetic Theory o The classic approach attributed control of skull growth largely to intrinsic genetic factors o “Coming from within” / Pre-programmed 2. Sutural Dominance Theory o Proposed by Weinmann and Sicher o All osteogenic tissues, that is, cartilage sutures and periosteum, were thought to play an equally significant role in the control of the growth of the skull. 3. Cartilaginous Theory o Scott proposed that intrinsic, growth-controlling factors were present only in the cartilage and in the periosteum. o Growth in the sutures was secondary and entirely dependent on the growth of the cartilage and adjacent soft tissues. 4. Functional Matrix Hypothesis o “the origin, form, position, growth and maintenance of all the skeletal tissues and organs are always secondary, compensatory and necessary responses to chronologically and morphologically prior events or processes that occur in specifically related non skeletal tissues, organs or functioning spaces” o The craniofacial skeleton, like all skeletal structures throughout the body, develops initially and grows in direct response to its extrinsic, epigenetic environment.  Internal construction of bone Trajectories - Bony strips that adhere to lines of force transmission.