The document discusses prenatal human growth and development, beginning with definitions of growth and development and covering topics such as critical periods, signaling growth factors, prenatal development including pre-implantation, embryonic, and fetal periods, postnatal development, osteogenesis, basic growth movements, theories of growth, and normal and abnormal development. It provides details on the derivation and development of structures from the germ layers and pharyngeal arches during important periods such as pre-somite, somite, and post-somite.

1. GROWTH AND DEVELOPMENT

2. 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

3. CONTENTS CONT’D
 Osteogenesis
a) Endochondral
b) Intramembranous
 Basic growth movements
a) Remodelling
b) Displacement
 Calvaria
- Growth of calvaria
 Theories of Growth
 Growth Spurts
- Importance

4. CONTENTS CONT’D
 Normal features of growth and development
-Pattern
a. Proportionality
-Differential Growth
- Cephalocaudal gradient of growth
b. Predictability
-Variability
c)Timing, Rate & Direction
 Formation of Face
 Abnormal development

5. ―There must be a beginning on any great matter ,but the
continuing unto the end until it be thoroughly finished, yields the
true glory‘‘
-Sir Francis Drake(1587)

6. 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)

7.  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)

8. 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)

9. CORRELATION BETWEEN GROWTH AND
DEVELOPMENT
 Growth is basically anatomic phenomenon and
quantitative in nature.
 Development is basically physiologic phenomenon
and qualitative in nature.
9

10. CRITICAL PERIODS
Genes orchestrate the phenomena of normal growth and
development
Stage 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)

11. 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.

12. 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

13. PRENATAL DEVELOPMENT
PRE
EMBRYONIC FETAL
IMPLANTATION
• 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

14. PREIMPLANTATION PERIOD
Morula
Initial stages of embryogenesis, depicting cell division

15. PREIMPLANTATION PERIOD
CLEVAGE
After approximately 3 days
of fertilization
cells of the embryo divide
to form a 16 cell morula

16. PREIMPLANTATION PERIOD
The morula transforms into a blastocyst
containing a cavity called blastocoele.

17. PREIMPLANTATION PERIOD

18. PREIMPLANTATION PERIOD
CHORIONIC CONNECTION [7th day]

19. EMBRYONIC PERIOD
Pre somite – 8 – 21 days
Somite – 21 – 31 days
Post somite – 32 – 56 days

20. 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

21.  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.

22. 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

23. 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

24. PRIMITIVE STREAK

25. 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

26. 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.

27. STOMATODEUM
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

28. FRONTONASAL PROCESS
• Mesoderm
• Proliferates-downward
projection

29. 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.

30. PHARYNGEAL ARCHES
Developing pharyngeal arches that
appear in the 4 or 5th week of development.

31. SOMITE PERIOD
 Structures in pharyngeal arhces

32. The neural crest cells that originate in the neuroectoderm of
the forebrain, midbrain and hindbrain migrate ventrally into
the pharyngeal arches.

33. CATEGORIZATION OF PORTIONS OF THE CENTRAL
NERVOUS SYSTEM
 Rhombencephalon
 Prosencephalon
RHOMBENCEPHALON
 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

34. PROSENCEPHALON
The prosencephalon (or forebrain) is the rostral-most (forward-most)
portion of the brain.
The prosencephalon, the mesencephalon (midbrain), and
rhombencephalon (hindbrain) are the three primary portions of the brain during
early development of the central nervous system

35. DERIVATIVES OF PHARYNGEAL ARCHES
ARCHES NERVE MUSCLES SKELETAL ARTERY
I Maxillary arch Trigeminal MOM Mandible, Maxilary
Maxilla,incus,
malleus
II 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 hyoid
IV & VI Sup laryngeal & Intrinsic muscles Thyroid, cricoid, IV- rt subclavian
recurrent of larynx, arytenoid,
laryngeal pharynx, levetor corniculate, VI - pulmonary
palatini cuneform

36.  Derivatives of Pharyngeal pouches

38. BRANCHIAL ARCH CARTILAGES
 The initial skeleton of the branchial arches develops from the mesenchymal
tissue as cartilaginous bars.

39. 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

40.  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.

41. 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.

42. FETAL PERIOD (7 MONTHS)

43. 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.

44. 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.

45. POST NATAL GROWTH
What 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.

46. TERMINOLOGIES
 Primary cartilage
 Secondary cartilage
 Growth centre – location at which independent
growth occurs
 Growth site – mere location at which growth occurs

47. 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

48.  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

49. 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 ways
1) Endochondral
2)Intra-membranous

50. 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‘‘

51. MEMBRANOUS OSSIFICATION
Occurs 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

52. BASIC GROWTH MOVEMENTS
A)REMODELLING
B)DISPLACEMENT
Eg: In a joint, bone enlarges in a given direction
within the joint, it is simultaneously displaced in
the opposite direction.

53. 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.

54. 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

55. The surface that faces the direction of growth is
depository.
if rates of deposition and resorption are
equal, the thickness of the cortex remains

56. 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 opposite
o 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

57. 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

58. • 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.

59.  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.

60. GROWTH OF CALVARIA
• As the brain expands, the separate bones of the calvaria are displaced in
outward directions.
(Functional matrix theory)

61. • Primary displacement of the bones causes tension in the sutural
membranes…. deposition of bone on the sutural edges.
• Sutural growth predominates until 4 yrs of life.

62. • Deposition on ectocranial and endocranial sides
• The endosteal surfaces lining the inner and outer cortical
tables are resorptive Increase in the overall
thickness of the bone while expanding the medullary space.

63. • The arch of curvature of the whole bone decreases.

64. • 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.

65.  Thecranial cavity thus achieves
 87% of its adult size by 2 years
 90% by 5 years
 98% by 15 years

66. THEORIES OF GROWTH CONTROL

67. THEORIES OF GROWTH
The major theories of growth are as follows
• Genetic Theory
• Remodelling Theory
• Sutural Theory
• Cartilageneous Theory
• Functional matrix Theory
• Servosystem Theory
• Van Limborgh‘s Theory

68. Other theories related to craniofacial growth are –
 Enlow‘s expanding ‗V‘ principle
 Enlow‘s counterpart principle
 Neurotrophic process in oro-facial growth

69. 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

70. 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

71.  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

72. 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 transplanted
b) Growth occurs in cleft lip and cleft palate patients even if suture not
present
c) Suture also respond to external influence
Contradiction: Koski(1968)- suture does not have its independent growth
potential

73. CARTILAGINOUS THEORY(JAMES SCOTT)
 Ex: Condylar cartilage for mandible
Nasal cartilage for maxilla
(nasomaxillary complex)

74. 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

75. Schematic representation of the functional matrix hypothesis of
craniofacial growth.
-Primary growth of the capsular matrix (brain) results in a stimulus for
secondary 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 and
bone growth of the temporal line (microskeletal unit).

76. 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

77. 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

78. 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

79.  "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.

80. 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

81.  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

82. 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

84.  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

85.  Imbalances in the regional relationship are produced by
differences in
Amount
Direction
Time of growth between the counterparts

86. GROWTH SPURTS

87. 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

88. BIOLOGICAL CHANGES SEEN DURING
PUBERTY
In 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

89. • 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

90. Velocity curves for growth at adolescence showing
different timings for Girls and boys

91. 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.

92. NORMAL FEATURES OF
GROWTH & DEVELOPMENT
 PATTERN
a. Proportionality
- Differential Growth
- Cephalocaudal gradient of growth
b. Predictability
 VARIABILITY
 TIMING ,RATE & DIRECTION

93. 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

94. PROPORTIONALITY :
Can be defined as a set of constraints operating to
preserve the integration of parts under varying conditions
or through time - moyers

95. 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

96. SCAMMON’S GROWTH CURVE
The body tissues can be broadly
classified as
 Lymphoid
 Neural
 General
 Genital
Each of this tissues grow at different times
& rates

97.  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)

98. CEPHALO-CAUDAL GRADIENT OF GROWTH

99. 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

100.  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

101.  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

102.  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

103. Cephalocaudal Gradient of
growth

104. 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

105. 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

106. 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

107. TYPES OF NORMALITY
• STATISTICAL
• EVOLUTIONARY
• FUNCTIONAL
• ESTHETICAL
• CLINICAL
107

108. 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

109. 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

110.  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

111. 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

112. FORMATION OF FACE
 4th WEEK
Cardiac buldge

116. 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

117. 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

118. 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.

119. 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

120. ABNORMAL DEVELOPMENT

121. 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.

122. 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.

123. 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.

125. THYROGLOSSAL CYST AND FISTULA

126. MANDIBULOFACIAL DYSOSTOSIS OR TREACHER
COLLINS 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

127. FISSURAL CYSTS
 Cystic cavities which arise along the fusion of various bones or
embryonic processes and lined by epithelium.

128. MEDIAN RHOMBOID GLOSSITIS
 It results from persistence of the tuberculum impar and
characterised by a red smooth region anterior to the
foramen caecum.

129. ANKYLOGLOSSIA
This occurs as a result of incomplete degeneration of
cells while the body of the tongue is freed, so that the tip
of the tongue remains tied to the floor of the mouth.

130. 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.

131. BIFID TONGUE
 This is a malformation common in south American
infants and is the result of failure of the lateral lingual
swellings.

132. THANK YOU

133. THANK YOU

134. ADDITIONS

135. Spurt in growth of jaws occurs at about same time as the spurt in height

136. SCHEMATIC REPRESENTATION OF SEGMENTATION IN EARLY
EMBRYOGENESIS

137. PRIMARY GERM LAYERS
Prechordal plate Ectoderm Epithelium of skin
Outer membrane of Hair
Oropharyngeal membrane Sweat glands
Sebacious glands
Lacrimal glands
Rathke’s pouch
Ext’ acoustic meatus &
Outer layer of tympanic
membrane Adenohypophysis
Oral epithelium Neural tube Placodes
-Enamel Neurohypophysis Olfactory : sensory
-Taste buds Spinal cord :Peripheral nerves Lens : eye
-Salivary gland Brain Otic:inner ear
-Thyroid gland -Optic vessels : Retina
-Cranial nerves

138. MESODERM
Pre chordal mesoderm Paraxial somites Intermediate
Prosencephalic Sclerotomes:Bassiocciput Urogenital
system
orgainsing centre Myotomes: Cervical ,Suprahyoid
Glossal muscles
Dermatomes : Dermis & skin
Head mesenchyme
Lateral
Bld vessels &Lympatics Blood &Lymph cells Connective tissue
-Coverings of laryngeal
muscles
Cranial mesodermal derivatives