Growth is a physio chemical process which relates structure compostion size and shape (SALZMAN)
Stage at which individual has reached a particular age is reffrd as Maturatinal/Biologic age.During ths periods of rapid change & diffrntn,there are *critical periods During which, Developing tissues/organs are more susceptible to humoural and environmental insults leading to growth deficiency and resultant malformations
*Embryogenesis, immune system, during inflammation and wound repair
Total prenatal period: 40weeks(280 days)After 28 weeks, fetus considered viable
During first 2-3 days,Zygote progresses from a single-cell to a 16 cell cluster morula.no larger than the original ovum,
The morula transforms into a blastocyst containing a cavity called blastocoele.
Blastocyst developed from the morula implants into the decidual layer of the uterine wall
Blastocyst developed from the morula implants into the decidual layer of the uterine wallTheblastocyst attaches to the uterine epithelium with the formation of trophoblast cells, c is known as chorionic conn’.Wiith this conn’, nutrient supply reaches the blastcyst
3rdpri germ layer makes its appearance at beginning of third week,as a result of ectodermal proliferation & differentiation in caudal region of embryonic discDefects may lead to Holoprosencephaly/Agenesis of corpus callosum. It also gives rise to Pre oral Gut(Seessel’s pouch)
(Gene lim 1 is reg’d for orgnst’n of prim’ streak
is a depression between the brain and the pericardium in an embryo, and is the precursor of the mouth and the anterior lobe of thepituitary gland.The stomodeum is lined by ectoderm, and is separated from the anterior end of the fore-gut by the buccopharyngeal membrane.This membrane is devoid of mesoderm, being formed by the apposition of the stomodeal ectoderm with the fore-gut endoderm; at the end of the third week it disappears, and thus a communication is established between the mouth and the future pharynx
The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres. In the human embryo eight rhombomeres can be distinguished, from caudal to rostral: Rh7-Rh1 and the isthmus (a borderline between midbrain and hindbrain in the most rostral part of the rhombomeres).
Prosencephalon:It controls body temperature, reproductive functions, eating, sleeping, and any display of emotionsAt the five-vesicle stage, the prosencephalon separates into the diencephalon (prethalamus, thalamus, hypothalamus, subthalamus, epithalamus, and pretectum) and the telencephalon (cerebrum). The cerebrum consists of the cerebral cortex, underlying white matter, and the basal ganglia.By 5 weeks in utero, it is visible as a single portion toward the front of the fetus. At 8 weeks in utero, the prosencephalon splits into the left and right cerebral hemispheres.When the embryonic prosencephalon fails to divide the brain into two lobes, it results in a condition known as holoprosencephaly.
The endodermal epithelium of the pharyngeal pouches differentiate into a variety of important organs.From the 1st pouch ,the middle ear and the Eustachian tube develop.From the 2nd, the palatine tonsils originate.From the 3rd pouch, the inferior parathyroid and the thymus arise.From the 4th pouch, the superior parathyroid gland forms.From the 5th pouch, the ultimobranchial body develops
A Process of bone formation
Embryonic development & subsequent growth of bone result from transformation of this cartilage into osseous tissue
Bone is directly formed from fibrous periosteal membrane without a cartilage intermediary
Biochemical- at the molecular level….constant deposition and removal of ions to maintain blood calcium levels.the one that we are dealing with in facial morphogenesis is growth remodeling.
Membranous junctions allow narrowing and overriding of bones (called molding) after birth
This is a passive movement of the bones secondary to brain’s expansion. an eg of functional matrix at work
Growth is mainly affected by genetic factors, But can also be significantly affected by environment, in the form of nutritional status, degree of physical activity,ealth or illness and no of similar factors
of long bones, are the principal locations at which intrinsic, genetically regulated, primary growth of bone takes placeContradiction: Koski(1968)- suture does not have its independent growth potential
It says that cartilage acts as primary growth center and has a innate growth potential If it is transplanted it grows independently
It says that body has two elements a) skeletal element b) functional matrix
Synchondrosis: a type of cartilaginous joint in which the cartilage is usually converted into bone before adult life
The sudden increase in the growth of general body is called as growth spurt.
Biological changes differ with boys and girls
Pubertal increments offers best time for large no of cases for the orthodontic treatment Understanding the growth, predictability of future growth of maxilla, mandible and alveolar process helps in diagnosing and achieving excellent results of the mal-occlusionOrthopedic correction of maxilla and mandible
Cell diameter: 140um
Placode - Epidermal thickeningPit - Placodeinvaginates to form a cavityVesicle - Pit becomes detached from the epithelium, rounds up
Cysts and fistulae found along the midline of the neck usually develop from remnants of thyroglossal duct.Generally, thyroglossal cysts maybe found at any point along the course of the thyroglossal duct but it is usually found at the level of the hyoid bone and the thyroid cartilage.
Growth and development of cranium and face
GROWTH AND DEVELOPMENT
CONTENTS Definition of growth and development Critical period Signalling Growth factor Pre natal development- 1)Pre implantation period- 2)Embryonic period- a)Pre somite- b)Somite- c)Post somite period- 3)Fetal period Post natal development- Terminologies
CONTENTS CONT’D Normal features of growth and development-Patterna. Proportionality -Differential Growth- Cephalocaudal gradient of growthb. Predictability-Variabilityc)Timing, Rate & Direction Formation of Face Abnormal development
―There must be a beginning on any great matter ,but thecontinuing unto the end until it be thoroughly finished, yields thetrue glory‘‘ -Sir Francis Drake(1587)
DEFINITION Growth may be defined as a developmental increase in mass. In other words it is a process that leads to increase in the physical size of cells ,tissues ,organs or organisms as a whole (STEWART 1982) Growth refers to increase in size or number(PROFITT 1986) Growth may be defined as the normal changes in the amount of living substance (MOYER 1988)
Growth is an increase in the size of a living being or any of its parts, occurring in the process of development (STEDMAN 1990) Growth refers to increase in size ( TODD) Growth signifies an increase ,expansion or extension of any given tissue (PINKHAM 1994)
DEVELOPMENT Development is increase in complexity (TODD 1931) Development is used to indicate an increase in skill and complexity of functions( Lowrey 1951) Development is in complexity (Profitt 1986) The act or process of natural progression from a previous, lower, or embryonic stage to a later , more complex or adult stage(STEDMAN 1990) Development addresses the progressive evolution of a tissue(PIKNHAM 1994)
CORRELATION BETWEEN GROWTH AND DEVELOPMENT Growth is basically anatomic phenomenon and quantitative in nature. Development is basically physiologic phenomenon and qualitative in nature. 9
CRITICAL PERIODSGenes orchestrate the phenomena of normal growth and developmentStage at which individual has reached a particular age is referred as Maturatinal/Biologic age*CRITICAL PERIOD(Smith .D .W and Bierman.E.L,The Biologic Ages of Man, Philadelphia1973,W.B.Saunders Co)
CRITICAL PERIODS Eg: Most brain cells have been formed by 6 months of age, whereas Bone & Cartilage continue to divide for atleast 15-20years,as a consequence, brain is highly susceptible to phenomena producing growth deficiency disorders during fetal and early infancy,but the skletal is susceptible to both ,during prenatal and throughout childhood and adolescence.
SIGNALING GROWTH FACTORS Signaling centre: Group of cells that regulate the behavior of surrounding cells by producing positive and negative intercellular signals. Growth factors stimulate cell proliferation and differentiation by acting through specific receptors on responsive cells. They assume different roles at different times at different places. Most of these factors are present and active throughout the life
PRENATAL DEVELOPMENT PRE EMBRYONIC FETALIMPLANTATION• First 7 days • Next 7 weeks • Next 7 months SOMITE 21 T0 31 PRE DAYS POST SOMITE SOMITE 8 TO 21 32 TO 56 DAYS DAYS
PREIMPLANTATION PERIOD MorulaInitial stages of embryogenesis, depicting cell division
PREIMPLANTATION PERIOD CLEVAGE After approximately 3 days of fertilization cells of the embryo divide to form a 16 cell morula
PREIMPLANTATION PERIOD The morula transforms into a blastocyst containing a cavity called blastocoele.
PRE SOMITE PERIOD An embryo in any stage of development before the appearance of the first pair of somites (segments), which in humans usually occurs around 19 to 21 days after fertilization of the ovum
On day 15, a groove, called the primitive streak , appears on the surface of the midline of the dorsal aspect of the ectoderm of the embryonic disc. By day 16, a primitive knot of cells, the Henson’s node, appears at the cephalic end of the primitive streak. This knot gives rise to the cells that form the notochordal process.
PRE CORDAL PLATE Precordal plate: is an endodermal thickening ,appears in mid-cephalic region as a consequence of Sonic hedgehog(SHH)signalling Prechordal plate prefaces the development of the orofacial region giving rise later to endodermal layer of oropharyngeal membrane. It is believed to form head orgainising function
PRIMITIVE STREAK The Resultant bulge is called prim’ streak From primitive streak, the rapidly proliferating tissue known as mesenchyme ,forms intraembryonic mesoderm c migrates in all dir’ betwn ectoderm and endoderm,except at sites of oropharyngeal membrane Appearance of mesoderm converts the bilaminar disk into trilaminar structure
NEURAL TUBE Dev of ectoderm into its cutaneous and neural portions occurs at 20 days by infolding of neural plate ectoderm at the midline forming NEURAL FOLDS, this creates a NEURAL GROOVE,. At 22days,neural folds fuse in region of third to fifth somites ,the site of the future occipital region, Initial closure proceeds cephalically and caudally to form NEURAL TUBE
FATE OF GERM LAYERS Ectodermal cells will give rise to the nervous system; the epidermis and its appendages (hair, nails, sebaceous and sweat glands); the epithelium lining the oral cavity, nasal cavities and sinuses; a part of the intraoral glands, and the enamel of the teeth. Endodermal cells will form the epithelial lining of the gastrointestinal tract and all associated organs. The mesoderm will give rise to the muscles and all the structures derived from the connective tissue(e.g., bone, cartilage, blood, dentin, pulp, cementum and the periodontal ligament). The embryonic disc will soon become altered by bends and folds necessary for further development.
STOMATODEUMThis membrane is devoid of mesoderm, being formed by theapposition of the stomodeal ectoderm with the fore-gutendoderm; at the end of the third week it disappears, and thus acommunication is established between the mouth and thefuture pharynx
FRONTONASAL PROCESS • Mesoderm • Proliferates-downward projection
SOMITE PERIOD• When the buccopharyngeal membrane breaks down at the 4th week, the foregut communicates with the exterior through the stomatodeum• A series of mesodermal thickenings in the wall of the cranial most part of the foregut- pharyngeal / branchial arches.• In the interval between any two adjoining arches, the endoderm extends outward to form the endodermal pouch to meet the ectoderm which dips into this interval as an ectodermal cleft.
PHARYNGEAL ARCHES Developing pharyngeal arches that appear in the 4 or 5th week of development.
SOMITE PERIOD Structures in pharyngeal arhces
The neural crest cells that originate in the neuroectoderm ofthe forebrain, midbrain and hindbrain migrate ventrally into the pharyngeal arches.
CATEGORIZATION OF PORTIONS OF THE CENTRALNERVOUS SYSTEM Rhombencephalon ProsencephalonRHOMBENCEPHALON The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres. In the human embryo eight rhombomeres can be distinguished, from caudal to rostral: Rh7-Rh1 and the isthmus
PROSENCEPHALON The prosencephalon (or forebrain) is the rostral-most (forward-most)portion of the brain.The prosencephalon, the mesencephalon (midbrain), andrhombencephalon (hindbrain) are the three primary portions of the brain duringearly development of the central nervous system
DERIVATIVES OF PHARYNGEAL ARCHESARCHES NERVE MUSCLES SKELETAL ARTERYI Maxillary arch Trigeminal MOM Mandible, Maxilary Maxilla,incus, malleusII Hyoid Facial Muscles of facial Stapes, styloid Stapedial(embry expression process,lesser onic) cornu & upper Corticotympanic( part of body of adult) hyoid,III Glossopharynge Stylopharyngeus Gr. Cornu & Common carotid al lower part of body of hyoidIV & VI Sup laryngeal & Intrinsic muscles Thyroid, cricoid, IV- rt subclavian recurrent of larynx, arytenoid, laryngeal pharynx, levetor corniculate, VI - pulmonary palatini cuneform
BRANCHIAL ARCH CARTILAGES The initial skeleton of the branchial arches develops from the mesenchymal tissue as cartilaginous bars.
1ST ARCH In the 1st arch ,bilateral Meckel’s cartilages arise. The malleus and incus develop and ossify at the dorsal end of Meckels cartilage. The rest of the cartilage gradually disappears, leaving part of the perichondrium as the sphenomalleolar ligament (ant. Ligament of malleus) and part as the sphenomandibular ligament.2nd ARCH In the, Reichert’s cartilage develops. It gives rise to the stapes, styloid process, lesser horn and upper part of the body of the hyoid. The stylohyoid ligament is formed by the perichondrium at the site of disappearance of this 2nd arch cartilage
The 3rd arch cartilage forms the greater horn and lower part of the body of the hyoid. The 4th arch cartilage forms the thyroid cartilage. The 5th arch cartilage has no adult derivatives. The 6th arch cartilage forms the laryngeal cartilages.
POST SOMITE PERIOD 2ND MONTH OF DEVELOPMENT Facial features become more recognizable as human. The external appearance of the embryo is changed by an increase in head size and formation of limbs, face, ears, nose and eyes.
FETAL PERIOD• The period from the beginning of ninth week to birth is called FETAL PERIOD.• Growth in length is particularly striking during the 3rd, 4thand 5th months while an increase in weight mainly occurs during the last two months.• The length of pregnancy is considered to be 38 weeks or 266 days after fertilization.
FETAL PERIOD • At the beginning of the 3rd month,the head constitutes half of overall length. • Beginning of 5th month, head is one third of the total length and • At birth it is one fourth of the total length.
POST NATAL GROWTHWhat is post natal growth?? Post natal growth is the first 20 years of growth after birth.How does it defer from prenatal growth?? Prenatal growth is characterized by a rapid increase in cell numbers and fast growth rates Postnatal growth is characterized by declining growth rates and increasing maturation of tissues.
TERMINOLOGIES Primary cartilage Secondary cartilage Growth centre – location at which independent growth occurs Growth site – mere location at which growth occurs
TERMINOLOGIES Cortical drift – relocation of bone by simultaneous deposition and resorption processes on the opposing periosteal and endosteal surfaces Displacement – movement away from a certain position or place Primary displacement- occurring in conjunction with bone’s own growth Secondary displacement – caused by enlargement of adjacent or remote bones or soft tissues; but not of the bone itself
Remodeling – reshaping of the outline of the bone by selective resorption of bone in some areas and deposition in other areas Relocation – relative movement in space of a bony structure, due to bone deposition on one side and resorption on the other side
OSTEOGENESIS Def‘n Two basic type of cells capable of osteogenesis A)Undiffentiated mesenchymal cells B)Cells in bone marrow tissue Mechanisms of bone formation It takes place by two ways1) Endochondral2)Intra-membranous
ENDOCHONDRAL OSSIFICATION Precursor cartilage Occurs mainly in• tubular bones• cuboid bones• base of the skull• vertebral bodies• part of the pelvis. Largely responsible for elongation of individual bones ,thus constitutes mainly for increase in ―Height‖ or ―Growth‘‘
MEMBRANOUS OSSIFICATIONOccurs primarily in-the Calvarium,-the clavicles-body of mandible-spinal process of the vertebrae,-part of pelvis Thus increase in width of bones is largely due to menbranous ossification Final shape is due to osteoclastic resorption
BASIC GROWTH MOVEMENTSA)REMODELLINGB)DISPLACEMENTEg: In a joint, bone enlarges in a given direction within the joint, it is simultaneously displaced in the opposite direction.
A) REMODELLING• Biochemical remodeling• Secondary reconstruction of bone by haversian system and rebuilding of cancellous trabaculae.• Regeneration and reconstruction of bone following disease or trauma.
REMODELING process of reshaping and resizing each level within a growing bone as it is relocated sequentially into a DEPOSITION succession of new levels. of bone on surfaces towards the direction of enlargement Bone surface relocates in the direction of bone growth RESORPTION on the opposite bony cortex or cancellous bony trabaculae
The surface that faces the direction of growth is depository. if rates of deposition and resorption are equal, the thickness of the cortex remains
B) DISPLACEMENT Is a movement of the whole bone by a physical force that carries it away from its contacts with other bones A)Primary displacement• The amount of displacement equals the amount of new bone deposition.• The respective directions are always oppositeo B)Secondary Displacement• Not related to its own growth.• Anterior growth of the middle cranial fossa• and temporal lobes secondarily displace the• nasomaxillary complex anteriorly and inferiorly
THE CALVARIA• The endocranial surface of the calvaria is predominantly depository.• The lining bony surface of the cranial floor is mainly resorptive.• Circumcranial reversal line
• Main function to protect the brain.• Growth occurs by utilizing the sutural system and small deposits occur on the ectocranial and endocranial sides.• Cranial vault is one of the first regions of the craniofacial skeleton to achieve full size.• Ossification begins at the7-8th week of gestation and continues into adulthood.
The non ossified articulations at birth are sutures or fontanellae depending on their size. Premature ossification of any suture or fontanelle alters the growth of the skull and thus the midface and lower face.
GROWTH OF CALVARIA • As the brain expands, the separate bones of the calvaria are displaced in outward directions. (Functional matrix theory)
• Primary displacement of the bones causes tension in the suturalmembranes…. deposition of bone on the sutural edges.• Sutural growth predominates until 4 yrs of life.
• Deposition on ectocranial and endocranial sides• The endosteal surfaces lining the inner and outer corticaltables are resorptive Increase in the overallthickness of the bone while expanding the medullary space.
• The arch of curvature of the whole bone decreases.
• Major stimulus for calvarial growth is…..• Intra cranial hydrostatic pressure….. Correlates directly with enlarging brain volume.• Brain volume increases from• one quarter to three quarters in the first 2 yrs of life.• the final quarter of growth is completed in the next 15 years.
Thecranial cavity thus achieves 87% of its adult size by 2 years 90% by 5 years 98% by 15 years
THEORIES OF GROWTHThe major theories of growth are as follows• Genetic Theory• Remodelling Theory• Sutural Theory• Cartilageneous Theory• Functional matrix Theory• Servosystem Theory• Van Limborgh‘s Theory
Other theories related to craniofacial growth are – Enlow‘s expanding ‗V‘ principle Enlow‘s counterpart principle Neurotrophic process in oro-facial growth
GENETIC GROWTH ( BRODIE) It says, growth is controlled by genetic influence in all aspect. But it cannot be accepted in all cases. As it has been shown that the external factor have significant modifying effect on growth
REMODELLING THEORY (1930) The research by Brash on bone provided the foundation for the development of the first general theory of craniofacial growth—the remodeling theory
The principal tenets of the remodeling theory were that-a) bone only grows appositionally at surfaces.b) growth of the jaws is characterized by deposition of bone at the posterior surfaces of the maxilla and mandible, sometimes described as ―Hunterian‖ growth of the jaws.c) calvarial growth occurs via deposition of bone on the ectocranial surface of the cranial vault and resorption of bone endocranially
SUTURAL DOMINANCE THEORY(SICHER & WEIMANN1955) According to this theory, the connective tissue and cartilaginous joints of the craniofacial skeleton, much like epiphyses of the long bones are the principal locations at which intrinsic, genetically regulated, primary growth of bones take place. Limitation :a) lack of growth of suture if it is transplantedb) Growth occurs in cleft lip and cleft palate patients even if suture not presentc) Suture also respond to external influenceContradiction: Koski(1968)- suture does not have its independent growth potential
CARTILAGINOUS THEORY(JAMES SCOTT) Ex: Condylar cartilage for mandible Nasal cartilage for maxilla (nasomaxillary complex)
FUNCTIONAL MATRIX THEORY(MELVIN MOSS 1968))Functional matrix comprised of 1)periosteal component 2)capsular component Functional matrix has primary control on growth of skeletal unit and bone,which respond in passive manner but it can not explain all aspects of growth
Schematic representation of the functional matrix hypothesis ofcraniofacial growth.-Primary growth of the capsular matrix (brain) results in a stimulus forsecondary growth of the sutures and synchondrosis,-Leading to overall enlargement of the neurocranium (macroskeletal unit).-Function of the temporalis muscle exerts pull on the periosteal matrix andbone growth of the temporal line (microskeletal unit).
FUNCTIONAL MATRIX REVISITED.. 1. The role of mechanotransduction Melvin L. Moss 1997 July 2. The role of an osseous connected cellular network 1997 August 3. The Genomic thesis 1997 September 4. The Epigenetic antithesis and the Resolving synthesis 1997 October
1ST AND 2ND .. The addition to the FMT, the concepts of mechanotransduction and of computational bone biology offers an explanatory chain extending from the epigenetic event of skeletal muscle contraction, hierarchically downward, through the cellular and molecular levels to the bone cell genome, and then upward again, through histologic levels to the event of gross bone form adaptational changes. Analyzing size and shape changes by reference-frame-invariant, finite element methods produces a more comprehensive and integrated description of the totality of the processes of epigenetic regulation of bone form than previously possible
3RD AND 4TH .. The first two articles in this series, by emphasizing the roles of a number of biophysical and biochemical factors in the regulation of morphogenesis, implicitly argued for the correctness of the fundamentally epigenetic thrust of the FMT However, the regulatory primacy of either genomic (genetic) or of epigenetic factors and/or processes in morphogenesis continues debated, it seemed useful to re-evaluate this nontrivial matter
"IT IS A WIN-WIN SITUATION― Individually both are necessary causes, but neither are sufficient causes alone. Together they provide both the necessary and sufficient causes for the control (regulation) of morphogenesis Nevertheless, epigenetic processes and events are the immediately proximate causes of development Thus they are the primary agencies.
MULTI FACTORIAL THEORY(VAN LIMBORGH 1970) Intrinsic genetic factor: They are the genetic control of the skeletal unit themselves. Local epigenetic factor: Bone growth is determined by genetic control originating from adjacent structures like brain, eyes etc. General epigenetic factor: Genetic factors determining growth from distant structures. Eg: Sex hormones, growth hormones. Local environmental factor: Non genetic factors from local external environment. Eg: habits, muscle force General environmental factor: They are General Non genetic influences such as nutrition, oxygen etc
Chondrocranial growth is controlled mainly by intrinsic genetic factors. The cartilageneous part of the skull must be considered as the growth centres. Sutural growth is controlled mainly by influences originating from the skull cartilages and from other adjacent skull structures. Periosteal growth largely depends upon growth of the adjacent structures. Sutural and periosteal growth is additionally governed by local non genetic environmental influences
ENLOW’S EXPANDING ‘V’ PRINCIPLE Many facial bones or part of bone have a V shaped pattern of growth The growth movements and enlargement of these bones occur towards the wide ends of the V as a result of differential deposition and selective resorption of bone. Bone deposition occurs on the inner side of the wide ends of the V and bone resorption on the outer surface. The V pattern of growth occurs in a number of regions such as base of the mandible, ends of long bones, mandibular body, palate etc
Enlow’s counterpart principle The growth of any given facial and cranial part relates specifically to other structural and geometric counterparts in the face and cranium The different parts and their counterparts are : Nasomaxillary complex relates to the anterior cranial fossa Horizontal dimension of the pharyngeal space relates to the middle cranial fossa. Middle cranial fossa and breadth of the ramus Maxillary and mandibular dental arch Bony maxilla and corpus of the mandible. Maxillary tuberosity and the lingual tuberosity
Imbalances in the regional relationship are produced by differences in Amount Direction Time of growth between the counterparts
GROWTH SPURTS Refers to Sudden increase in growth of general Body. Woodside in his study of Burlington Group showed. Girls Boys Just after birth 3 yrs 3 yrs Juvenile growth Spurt 6-7yrs 7-9yrs Pubertal growth spurt 10-12yrs 12-15yrs 87
BIOLOGICAL CHANGES SEEN DURINGPUBERTYIn Boys :• Stage I:- Fat spurt - Initially maturing boy gains weight and becomes chubby –production of estrogen before production of testosterone.• Stage II- Spurt in height, development of secondary sexual characteristics.- Occurs 1 year after the Stage I• Stage III- Occurs 8-10months after stage II and coincides with the peak velocity with gain in height- At this stage auxillary hair appears and facial hair appears on upper lip.- Spurt in muscle growth occurs
• Stage IV:- Occurs from 15-24 months after stage III- Spurt of growth in height ends. Facial hair on chin and upper lip. This indicates growth is almost complete.In Girls: Stage I:- Beginning of growth spurt appearance secondary sexual characteristics . Stage II:- Occurs 1 year after stage I coincides with peak velocity physical growth. Stage III:- Occurs 1-1½ years later stage II. marked by onset of menstruation.- By this time growth spurt all but complete. 89
Velocity curves for growth at adolescence showingdifferent timings for Girls and boys
IMPORTANCE OF GROWTH SPURTS: Pubertal increments. Determining and understanding the predictability, growth direction&total treatment time. Orthopedic correction Growth spurts serve as excellent indicators for timing of orthodontic treatment Correlation of a. Skeletal age, b. Dental age c. Chronological age. With onset of puberty.
NORMAL FEATURES OFGROWTH & DEVELOPMENT PATTERN a. Proportionality - Differential Growth - Cephalocaudal gradient of growth b. Predictability VARIABILITY TIMING ,RATE & DIRECTION
PATTERN : Pattern represents proportionality-not just proportional relationships at a point in time but change in these relationships over time Physical arrangement of the body at one time is a spatially proportioned parts . But ,there is a higher level pattern, the pattern of growth, which refers to the changes in these spatial proportions over time
PROPORTIONALITY : Can be defined as a set of constraints operating to preserve the integration of parts under varying conditions or through time - moyers
DIFFERENTIAL GROWTH Not all tissue systems of the body grow at the same rate. Different tissues and different organs grow at different rates. This process is called differential growth.Eg :Muscular & skeletal – grow faster than brain and CNS as reflected in the relative decrease of head size 95
SCAMMON’S GROWTH CURVE The body tissues can be broadly classified as Lymphoid Neural General GenitalEach of this tissues grow at different times & rates
As the graph indicates growth of neural tissues is complete by 6-7 years of age General body tissue, including Muscle, Bone, Viscera show S shaped curve, with a definite slowing of growth rate during childhood and an accelertaion at puberty. Lymphoid tissues proliferate far beyond the adult amount in late childhood, and then undergo involution and at the same time that growth of the genital tissues accelerate rapidly.(Scammon RE: The measurement of body in childhood)
CEPHALO-CAUDAL GRADIENT OF GROWTH It simply means there is an axis on increased growth extending from head towards the feet. A comparision of body proportion of pre natal and post natal growth reveals that postnatal growth of regions of body that are away from hypophysis is more. Represents the changes in over all body proportions during normal growth and development
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 the face, so that proportion of entire body devoted to head has decreased to about 30% 100
The overall pattern thereafter follows the course, a progressive reduction of relative size of the head to about 12% of the adult. Thus the name Cephalocaudal gradient of growth, meaning there is an axis of increased growth, extending from head towards the feet
At 3rd month of IUL head 50% of total body length. At birth head 30% of total body length. At adult head 12% of total body length. Post natally, head grows larger than the cranium
PREDICTABILITY Predictability of growth pattern is a specific kind of proportionality that exists at a particular time and progresses towards another, at the next time frame with slight variations. Change in growth pattern :(expected changes in body proportions). 104
VARIABILITY No two individuals with the exception of siamese twins are like. Hence it is important to have a ―normal variability‖ before categorizing people as normal or abnormal 105
NORMALITY Normality refers to that which is usually expected, is ordinarily seen or typical – Moyers Normality may not necessarily be ideal. Deviation from usual pattern can be used to express quantitative variability This can be done by using ―growth charts‖ 106
TYPES OF NORMALITY• STATISTICAL• EVOLUTIONARY• FUNCTIONAL• ESTHETICAL• CLINICAL 107
TIMING OF GROWTH One of the factors for variablity in growth. Timing variations arise because biologic clock of different individuals is different. It is influenced by:• genetics• sex related differences• physique related• environmental influences
AGE EQUIVALENCE Because of variability and timing all individual at a given chronological age are neither of the same size or same stage of maturation. It is better to compare biologic development. ―Developmental ages‖ –skeletal age and dental age are used. 109
The mating of male& female gametes in the maternal uterine tube initiates the development of zygote- the first identification of an individual Cell diameter: 140um
FORMATION OF FACE• At the end of the fourth week, the centre of the face is formed by the stomodeum, surrounded by the first pair of pharyngeal arches• Five mesenchymal prominences can be recognized: mandibular prominences (caudal) maxillary prominences (lateral) nasomaxillary prominence(cranial)• These prominences arise from the neural crest ectomesenchyme that migrate into the facial and neck regions
NASOLACRIMAL DUCT• Within the grooves between the lateral nasal and maxillary prominences, solid rods of epithelial cells sink into the subjacent mesenchyme.• These rods extend from the developing conjunctival sacs at the medial corners of the forming eyelids to the external nares.• Later canalise to form the nasolacrimal sacs and ducts which become completely patent only after birth
FORMATION OF THE EYES• Thickened epithelial lens placodes invaginate concomitantly with formation of optic vesicles – deep set eyeballs.• Medial migration of the eyes from their initial lateral position.• Folds of surface ectoderm grow over the eyes - eyelids
FORMATION OF THE EARS The internal ear manifests as a hindbrain induction of surface ectodermal cells – thickened otic placode. Placode pit vesicle internal ear. The external ear develops in the region of the neck as 6 auricular hillocks surrounding the 1st pharyngeal groove. The middle ear develops from the 1st pharyngeal pouch.
FORMATION OF THE NOSE The bridge is formed from the frontal prominence. the merged medial nasal prominence forms the median ridge and the tip. The alae are formed by the lateral nasal prominence and the cartilagenous nasal capsule gives rise to the septum and nasal conchae
ABNORMAL DEVELOPMENT Cleft Lip: Can be unilateral, bilateral and can vary from a notch in the vermillion border to a cleft extending into the floor of the nostril. Cleft palate: Less common than cleft lip. It maybe due to lack of growth or failure of fusion between the median and lateral palatine processes and the nasal septum or it maybe due to initial fusion with interruption of growth at any point along its course. It may also be due to interference with elevation of palatal shelves.
CERVICAL CYSTS AND FISTULAE: Caudal overgrowth of the second arch gradually covers the 2nd, 3rd and 4th branchial grooves. These grooves lose contact with the outside and temporarily form an ectoderm lined cavity, the cervical sinus, which should normally disappear. Failure of complete obliteration of the cervical sinus results in a cervical cyst.
CERVICAL CYSTS AND FISTULAE: If the cyst opens to the outside, a fistula develops. Branchial cysts or fistulae are found anywhere on the side of the neck along the anterior border of the SCM muscle. Another cause is incomplete caudal overgrowth of 2nd arch, which leaves an opening on the surface of the neck.
MANDIBULOFACIAL DYSOSTOSIS OR TREACHERCOLLINS SYNDROME:. This results from failure or incomplete migration of the neural crest cells to the facial region. The zygomatic bone is severely hypoplastic . The face appears to be drooping, and the ears are usually malformed. The lower border of the mandible appears concave, and cleft palate is occasionally seen
FISSURAL CYSTS Cystic cavities which arise along the fusion of various bones or embryonic processes and lined by epithelium.
MEDIAN RHOMBOID GLOSSITIS It results from persistence of the tuberculum impar and characterised by a red smooth region anterior to the foramen caecum.
ANKYLOGLOSSIAThis occurs as a result of incomplete degeneration ofcells while the body of the tongue is freed, so that the tipof the tongue remains tied to the floor of the mouth.
MACROGLOSSIA Macroglossia or abnormally large tongue is not common, but is seen sometimes at birth when tongue slightly protrudes from mouth. This corrects itself when the jaws grow at a rapid rate. True macroglossia is seen in mongolism.
BIFID TONGUE This is a malformation common in south American infants and is the result of failure of the lateral lingual swellings.