Lecture 1 Craniofacial Growth PDF

Craniofacial growth and Development Lecture 1  Introduction Dentist and orthodontist are heavily involved in the development of not only the dentition but of the entire dento-facial growth complex, a thorough background in craniofacial growth and dev...

Craniofacial growth and Development Lecture 1  Introduction Dentist and orthodontist are heavily involved in the development of not only the dentition but of the entire dento-facial growth complex, a thorough background in craniofacial growth and development is necessary  GROWTH Growth, in a biological sense, is usually defined as an increase in size or weight of a tissue, an organ or an individual.  Development Development is progress towards maturity. Orderly and sequential changes that take place overtime from conception till death.  Maturation Final outcome in which peak of development is attained Importance of measuring growth and development Monitor Monitor stage of growth for Education Research health dental treatment  Growth 1. Pattern of growth 2. Type of growth 3. Phases of growth 4. Differential growth Scammon’s growth curve Cephalic-caudal gradient of growth 5. Growth spurt Patterns of Growth Isometric growth Allometric growth  Isometric growth An organ grows at the same rate as the rest of the body. As the organism grows, the size remains proportional. Example: Fish.  Allometric growth the organ grows at a different rate from which the body grows. The external form of the organism changes as the body grows. Example: Mammals.  Growth 1. Pattern of growth 2. Type of growth 3. Phases of growth 4. Differential growth Scammon’s growth curve Cephalic-caudal gradient of growth 5. Growth spurt Types of Growth Multiplicative Auxetic or Embryonic growth growth Accretionary Appositional growth growth  Multiplicative or Embryonic growth In multicellular organisms, growth occurs by an increase in the number of cells of the organism due to mitotic cell division. Example: Growth of embryos and prenatal growth in mammals.  Auxetic growth In some organisms like Ascaris, growth occurs as a result of increase in the size of their cells. The number of cells remains the same. The body grows in size because of the enlargement of its cells. In certain tissues of higher animals like the body muscles, auxetic growth is seen.  Accretionary growth During post embryonic growth, and also in the adult, all the body cells are not capable of undergoing division. This is because they have become differentiated. But at some locations, undifferentiated cells are present which divide mitotically and replace the worn out differentiated cells as and when needed. These cells are called reserve cells.  Accretionary growth Example: Bone marrow of vertebrates contains unspecialized cells that continuously produce blood cells to replace worn out ones.  Appositional growth It is the addition of new layers on the previously formed layers. It is the characteristic type of growth, seen in rigid materials like bone.  Growth 1. Pattern of growth 2. Type of growth 3. Phases of growth 4. Differential growth Scammon’s growth curve Cephalic-caudal gradient of growth 5. Growth spurt  Phases of growth Lag period Exponential Deaccelerating period growth period  Phases of growth 1) Lag period: It is the first period during growth phase, where the curve rises gradually. The organism is getting prepared for growth by synthesizing enzymes and accumulating substances to metabolize protoplasmic components.  Phases of growth 2) Exponential period: During this period growth begins slowly at first and becomes rapid later on. Hence the curve rises steeply. As a result, the organism enlarges doubling and redoubling in size. This phase is also called as logarithmic phase.  Phases of growth 3)Deaccelerating growth period: The exponential growth does not continue indefinitely. It is followed by a period when growth proceeds more slowly and finally cease altogether. The curve therefore rises slowly and these become horizontal, signifying limit of growth. During this phase, the rate of acceleration is exactly equal to catabolism. Stages of Growth Period in Man Prenatal period Postnatal period  Prenatal period The prenatal period comprises, on the average, about 9 months. A fertilized egg of a multicellular animal is transformed into an embryo by cell division, growth and differentiation. This growth into the embryo is called prenatal growth.  Prenatal period Prenatal growth has three distinct stages: Fertilized ovum (egg), or zygote (first 2 weeks). Embryo (from 2 to 8 weeks). Fetus (from 2 to 9 lunar months).  Prenatal period During the first part of this period, the ovum is like a homogeneous mass. During the embryonic stage, although the rate of growth is slow, yet differentiation occurs in this mass to give rise to different parts, like head, arm, leg and others.  Prenatal period By the eighth week, the embryo becomes child-like in appearance. During fetal stage, the rate of growth in length as well as weight is considerably high. Hence, in the prenatal period (before birth), the embryo is formed with rudiments of all organs and systems.