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UNIT 1 CONCEPT OF DEVELOMENT,
GROWTH AND DEVELOPMENT,
LIFE SPAN PERSPECTIVE,
METHODS OF STUDYING
DEVELOPMENT AND
CHARACTERISTICS OF
DEVELOPMENT
Structure
1.0 Introduction
1.1 Objectives
1.2 Concept of Development 1.2.1 Goals of Development Changes
1.3 Growth and Development
1.3.1 Critical Period During Development
1.4 Life Span Perspectives
1.4.1 Understanding Life Span Development 1.4.2 Issues in Life Span Development. 1.4.3 Stages of Human Development 1.4.4 Domains of Human Development
1.5 Characteristics of Life Span Development
1.6 Facts of Development
1.7 Research Methods for Life Span Development
1.8 Obstacles in Studying Life Span Development
1.9 Let Us Sum Up
1.10 Unit End Questions
1.11 Suggested Readings and References
1.12 Answer to Self Assessment Questions
1.0 INTRODUCTION
From the moment the human child is first conceived, to the day the individual dies, they keep changing constantly and developing. While some of the changes humans undergo are as a result of chance incidents and personal choices, the vast majority of life changes and stages the human passes through are due to certain common biological and psychological factors partly inherited and partly environmental and are shared by all people.
Development refers to the biological and psychological changes that occur in human beings between birth and the end of adoloscent, as the individual progresses from dependency to increasing autonomy. Because these developmental changes may be
Prenatal, Infancy and Early Childhood
6
strongly influenced by the genetic and enviornmental factors during prenatal life and these are the part of the study of child development. Developmental change may occur as a result of genetically-controlled processes known as maturation, or as a result of environmental factors and learning, but most commonly involves an interaction between the two. Developmetal psychology refers to development throughout the lifespan, and pediatrics, the branch of medicine relating to the care of children.
In this unit we are also going to introduce the concept of life span development. It deals with important developmental stages that human beings go through birth, infancy, adolescence, adulthood, old age and death. As the humans grow up from one stage to another stage they learn to make use of their body parts, learn how to express themselves and communicate with persons, learn how to maintain relationship with others and how to love and care for others. In this unit we will be focusing on the concept of development, issues and stages. In development of humans, and then put forward the concept of life span development, and its characteristics and theories of child development.
1.1 OBJECTIVES
After go through this unit, you will be able to: z define the concept of human development; z describe about the growth and development; z explain life span perspectives; z explain the significant issues involved in the process of human development ; z identify the stages and important domains of development; z analyse the characteristic features of life span development; and z explain the research methods and its obstacles in studying the life span.
1.2 CONCEPT OF DEVELOPMENT
Development describes the growth of humans throughout the lifespan, from conception to death. It refers to development as patterns of change over time. It does not just involve the biological and physical aspects of growth, but also the cognitive and social aspects related to the development. The scientific study of human development seeks to understand and explain how and why people change throughout life. This field examines change across a broad range of topics including motor skills and other psycho physiological processes. Cognitive development refers to the areas of problem solving, moral understanding, conceptual understanding, language acquisition, social, personality, and emotional development, and self-concept and identity formation. Growth is defined as an increase in size. In other words development is defined as a progression towards maturity. Even though development is a continuous process with competencies developing, then disappearing, only to appear at a later age, it is not continuous in the sense that it increases constantly but rather in a series of waves with whole segments of development reoccurring repetitively. For example, new borns walk, if held, and then this ability disappears only to reappear at eight or ten months of age.
1.2.1 Goals of Development Changes
The goal of development is to enable people to adapt to the environment in which they live. Self actualisation is essential to achieve these changes. It plays an important
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8
iii) Social and emotional: Children grow socially and emotionally. They learn how to interact, play, work, and live with other people such as family, friends, teachers, and employers. They learn how to understand both their own feelings and that of others’ emotions. They also learn ways of dealing with strong emotions. In order to function well as independent adults, children must develop a sense of self-esteem as they go through the long process of figuring out what shape their identity will take. They develop a sense of morality as they learn the difference between right and wrong. iv) Sexuality and gender identity: Children also develop sexually and form a gender identity. This development is unique because it spans developments across the other physical, psychological, and social channels. Early on, children learn how their bodies work and look and what it means to be a boy or a girl; they learn how boys and girls are different. As they grow older and enter adolescence and puberty, they continue to learn how their bodies work sexually and how to responsibly handle their sexuality so as to balance their sexual desires and appropriate behaviour. They continue to decide for themselves what it means to be masculine or feminine throughout their lifespan. Different theorists have come to different conclusions concerning how exactly children develop across the various developmental channels. Some theorists believe that children develop smoothly and continuously, but other theorists believe that children develop more discretely in a series of stages, each of which is fairly stable.
1.3.1 Critical Periods During Development
There are certain periods of development known as difficult periods or critical periods. It is said that children who do not get special stimulation during their time of receptivity may get stuck at this period. For instance children learn to trust the parents if parents are consistently loving, affectionate and give the child care and love unconditionally. In such cases the child learns to trust its parent and from then onwards other adults in the environment. However if the child is neglected and abused , not given the care, affection and love, he or she may develop distrust of parents and this distrust will be transferred to other adults in the environment. It must be remembered that even though the child’s development may have been adversely affected, if he or she is given an opportunity to be with foster parents who care and love the child, the latter develops the capacity to trust other adults too in course of time.
1.4 LIFE SPAN PERSPECTIVES
Life span refers to the ongoing process that we go through while growing up. It is the period of time from conception extending to death. Studying life span development is very important because it helps in describing and explaining the mysteries of human development. Life span development includes issues such as the extent to which development occurs through the gradual accumulation of knowledge versus stage like development, or the extent to which children are born with innate mental structures versus learning through experience. Many researchers are interested in the interaction between personal characteristics, the individual’s behaviour, and environmental factors including social context, and their impact on development. The scientific study of development is important not only to psychology, but also to sociology, education, and health care. By better understanding how and why people change and grow, one can then apply this knowledge to helping people live up to their full potential. Life span development is defined as the pattern of change that
begins at conception and continues through the life cycle.
Lifespan development can also be defined as a methodical, intra-individual change associated with progressions corresponding to age. The development progresses in a manner implicating the level of functioning.
Life-span developmental psychology is the field of psychology which involves the examination of both constancy and change in human behaviour across the entire life span, that is, from conception to death (Baltes, 1987). Development occurs in different domains, such as the biological (changes in our physical being), social (changes in our social relationships), emotional (changes in our emotional understanding and experiences), and cognitive (changes in our thought processes). Some developmental psychologists prefer to restrict the notion of development only to changes which lead to qualitative reorganisation in the structure of a behaviour, skill or ability (Crain, 2000).
Lifespan development is a process in which the progression initiates with the emergence of a fetus from a one celled organism. As the unborn child enters the world, the environment in which the child exists begins to influence the child’s development (Educational Foundation, 2001).
The developmental periods are child and adolescence, early adulthood, middle adulthood and late adulthood. The transition in each of the developmental periods, involves a necessary change in the character of the individual’s life and sometime this takes up to six years to complete the change (Smith, 2009).
The transition deals with the common developmental stages that human beings pass through: birth, infancy, adolescent, adulthood, old age and death.
1.4.1 Understanding Life Span Development
Human development is a multidisciplinary study of how people change and how they remain the same overtime. It reflects the complexity and uniqueness of each person and their experiences as well as commonalities and patterns across people. There are four interactive forces that combine to shape human development and these are given below:
i) Biological forces include all genetic and health related factors that influence the development of a child. They provide raw materials (in case of genetics) and set boundary conditions (in the case of one’s health) for development. Prenatal development, brain maturation, puberty, menopause, facial expression and change in cardio-vascular functioning, diet, and exercises are the some example of biological forces.
ii) Psychological forces include all internal perceptual, cognitive, emotional and personality factors that affect the development of a child. Intelligence, self confidence, honesty and self esteem are examples of psychological factors.
iii) Socio-cultural forces include interpersonal, societal, cultural and ethical factors that affect the development of a child. This is important to know that how people and environment interact with each other. The family, peers, coworkers and social institutions and culture influence development. Poverty is the example for socio cultural forces.
iv) Life cycle forces reflect differences in how the same event affects people of different ages. Each individual is a product of a unique combination of these forces. No two individuals even in the same family experience these forces in the same way.
Concept of Develoment, Growth and Development, Life Span Perspective, Methods of Studying Development and Characteristics of Development
1.4.3 Stages of Development
Often, developmental stages are defined by milestones. The term milestone refers to the development that has to take place according to the age of the child. For instance, almost all children start standing and walking at the age of 1 year and more, start saying a few words by the time they are one and half to two years etc. That a developmental stage has been successfully passed is indicated by the child mastering the developmental tasks of the particular period of development. Often, special milestones mark children’s accomplishments, such as walking in infancy and entering school in early childhood, and these milestones can help mark children’s movement inside and between developmental stages.
Individuals pass various stages throughout their life. There are systematic progressions in a certain order through a series of phases. Step by step they move closer to some form of adult status. This movement can be seen as involving changes in intellectual and physical powers (Example, changes in intelligence, expertise and ability to reason) and the impact of life events and experiences.
The main developmental periods of a human being are:
i) Childhood and adolescence {birth to age 20 (early childhood transition by age 03)}
ii) Early adulthood (age 17 to 45)
iii) Middle adulthood (age 40 to 65)
iv) Late adulthood (over 60 years of age) (Tennat and Pogson, 1995)
1.4.4 Domains of Human Development
The domains of development are categories used by scientists. The categories include physical, cognitive and social domains which all characterise human development. The physical domain is characterised by how humans grow and change physically, at all stages of development especially during childhood and adolescence. When the physical changes are maximum, this domain includes how humans view the world as development progresses as a result of physical development and interactions.
Psychological domain focuses on adjustment of the individual to the environment. Adjustment is the process which is essential for survival of the organism. The child has to learn to suck, ingest food, eliminate, breath on own, eliminate on own etc, which activities were taken care of when the child was still within the mother’s womb.
Adjustment also is required as the child grows up to learn to eat on own, eliminate as is required and not as the child wishes. The child has to learn to talk, walk, express, communicate and so on. All these adjustments are again necessary if the child has to survive.
Adjustment to self, others and environment are important tasks which become increasingly complex as the child grows up, and which all the child has to master and accomplish. Success leads to healthy adjustment while failure leads to maladjustment. Adjustments in the way the world is viewed as the body develops are also included in this domain.
Cognitive domain focuses on learning, attention, perception and memory etc. The manner in which learning takes place and how the child makes progress in school
Concept of Develoment, Growth and Development, Life Span Perspective, Methods of Studying Development and Characteristics of Development
Prenatal, Infancy and Early Childhood
and home are of great importance in the child’s growth and development. How these components of cognitive domain functions and improves indicate the progress the child makes. The social domain deals with the adjustment to people that are with others and learn the right ways of interactions. The cognitive domain is concerned with how learning occurs and why memory deteriorates during old age. The social domain contains adjustment in variables within social situations such as personality research, social skills and developing relationships. All the domains operate together and are affected by each other (Boyd & Bee, 2006).
Self Assessment Questions
State whether the statement is True or False.
Changes occur from conception to death. ( )
Children’s learning come from the society, his surroundings and his experiences. ( )
There are four areas in which children grow. ( )
Two interactive forces that combine to shape human development. ( )
Two interactive forces that combine to shape human development. ( )
Individuals pass only one stage through out the life. ( )
As the child grows ups adjustment to self, others and environment are important tasks which become increasingly complex. ( )
Psychological domain focuses on adjustment of the individual to the environment. ( )
1.5 CHARACTERISTICS OF LIFE SPAN
DEVELOPMENT
The lifespan perspective argues that significant modifications take place throughout development. It consists of development of humans in multidimensional, multidirectional, plastic, multidisciplinary, and contextual factors. The development involves three factors i.e. growth, maintenance and regulation.
Changes that occur are interpreted in terms of the requirements of the culture and context of the occurrences. According to Paul Baltes, humans have the capacity, plasticity and the ability for positive change to the environmental demands that are being made on the individual constantly. Individual learns ways and means to compensate and overcome difficulties throughout the life. According to Baltes positive characteristics of growing old such as learning ways to compensate and overcome (Boyd and Bee, 2006) are considered important characteristics of old age. These characteristics form a family of beliefs which specify a coherent view of the nature of development. It is the application of these beliefs as a coordinated whole which characterises the life-span approach. The important characteristics beliefs of the life span approach are given below:
- Lifelong development: This belief has two separate aspects. First, the potential for development extends across the entire life span, that is, there is no assumption that the life course must reach a plateau or decline during adulthood and old age. Second, development may involve processes which are not present
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Normative History Graded Influences : Biological and environmental influences that are associated with history that are common to people of a particular generation (example: Depression, the AIDS epidemic) also influences.
Non-normative Events : Unusual occurrences that have a major impact on an individual’s life; the occurrence, the pattern, and sequence of these events are not applicable to most individuals (e.g. Death of a parent at young age, getting a serious illness, winning a lottery).
1.6 FACTS OF DEVELOPMENT
We all know that development is the critical period for child development. Some significant facts must be taken into consideration to understand the pattern of development. Each of these has important implications and is explained as follows:
Early foundations are critical : Early foundations are critical because attitudes, habits and pattern of behaviour established during early years determine to a large extent how successfully individuals will adjust in their later life.
Role of maturation and learning in development: Maturation and learning play a significant role in the development. Maturation is unfolding individual’s inherent traits. Learning is development that occurs from experience and efforts on the individual’s part. Maturation provides the raw material for learning. Generally development is influenced by the interaction of both.
Development follows a definite and predictable pattern : It follows a definite and predictable pattern. There are orderly patterns of physical, motor, intellectual and speech development. Development is governed by certain laws: (i) Cephalocaudal Law – It means that development spreads over the body from head to foot and (ii) Proximodistal Law – It means that development spreads outward from the central axis of the body to extremities.
All individuals are different: No two people react in the same way to the same environmental stimuli and, one can never predict with accuracy how people will react to a situation. These individual differences are significant because they are responsible for individuality in personality make up.
Each Phase of development has characteristic behaviour: Each Phase has certain characteristic behaviours. The patterns are marked by periods of equilibrium, when individuals adapt easily to environmental demands and as a result make good personal and social adjustment and by periods of disequilibrium, when they experience difficulty in adaptation, make poor personal and social adjustment.
Hazards in each phase: Each stage is related to certain hazards such as physical, psychological and environment. These hazards inevitably involve adjustment problems. We should be aware of these hazards because awareness of these makes it possible to prevent or to at least alleviate these.
Development is aided by stimulation: While most development occurs as a result of maturation and environmental experiences, much can be done to aid development so that it will reach its full potential. Stimulation is especially effective at the time when ability is normally developing, though it is important at all times.
Cultural changes affect the development: An individual’s development is molded to confirm to cultural standards and norms, while changes in these standards affect the developmental pattern.
Every stage has social expectation: Every stage has certain societal expectation. The individual will be successful in fulfilling those expectations only if s/he is adhering to the rules and regulations of the family and society.
Traditional beliefs : Traditional beliefs about physical and psychological characteristics affect the judgments of others as well as their self evaluation. So long as these beliefs persist, they have a profound influence on the development pattern.
1.7 RESEARCH METHODS FOR LIFE SPAN
DEVELOPMENT
As you know development is a continuous process in a development of a child. It occurs over a life time period, thus we need to special techniques are employed to study the life span development. These techniques are discussed here:
Longitudinal method : For the study of developmental changes in the same group or individual, over a period of time, this method is useful. The same individual is tested at different age group. Example, case study of children behaviour in classroom.
Cross-section method: This method studies the development changes by testing individuals of different ages at the same time only once. This method helps to get the norms or standards of typical pattern of development for different age. This is faster and cheaper method than longitudinal method. It does not loose subjects who dropout of the study since the subjects are tested only once. Example for this method is eating behaviour of 5 years old.
Sequential method: To overcome the drawback of longitudinal and cross- sectional method this method was used. This is best method which combines the longitudinal and cross-sectional method. People in a cross-sectional sample are tested more than once and the results are analysed to determined the differences that show up overtime for the different groups of subjects. This method gives a more realistic assessment.
Time lag method: This method is studying the development of different age groups in different years to determine the effect of historical events on behaviour. This method is rarely used in developmental psychology, because it takes a long time and large numbers of subjects are required and have to be the same age at the time of testing.
Self Assessment Questions
Fill in the blanks.
The development involves three factors such as ———, ———— and —————.
Gains and losses in development occur throughout the ———————— development.
Multidimensional development occurs in the biological, —————and socio- emotional domains.
Maturation and ———— play a significant role in the development.
Concept of Develoment, Growth and Development, Life Span Perspective, Methods of Studying Development and Characteristics of Development
or using observational method for studying the behaviour, well-being, life satisfaction or happiness. The data vary for different age levels. The accuracy of such measures is questionable. Even through the longitudinal approach has a methodology advantage over the cross-sectional approach, the problem of accuracy is still ever present.
- Ethical aspects : The ethical aspect is a difficult task for the study of life-span development, as the rights of subject is to be considered by the researcher, even if the subject is being paid by the researcher for the study. Consent of the subject if adult and consent of parents/ guardians if child is an important and necessary step before data collection. These considerations also apply to younger or older subjects.
1.9 LET US SUM UP
In this unit we have studied about the concept of development, growth and development, meaning of life span development and methods of studying development. The key points of our discussion in this unit are:
Development refers to the biological and psychological changes that occur in human beings between birth and the end of adoloscent period as the individual progresses from dependency to increasing autonomy. Because these developmental changes may be strongly influenced by the genetic and enviornmental factors during prenatal life, these are the part of the study of child development Growth refers to the development of children from birth to adolescence.
There are four areas, in which children grow, i.e. (i) physical, (ii) psychological and cognitive, (iii) social and emotional and (iv) sexuality and gender identity. According to Educational Foundation (2001) lifespan development is a process beginning at conception that continues until death. The progression initiates with the emergence of a fetus from a one celled organism. As the unborn child enters the world, the environment in which the child exists begins to influence the child’s development.
There are four interactive forces that combine to shape human development and these are (i) biological forces, (ii) psychological forces, (iii) socio-cultural forces and (iv) life cycle forces.
Then we discussed about the issues, stages and important domains of development. Characteristics of life span development included many development as being lifelong and following a predictable pattern etc. To understand the pattern of development, certain fundamental facts must be taken into consideration. Each of these has important implications.
To know the developmental techniques we need to use some research methods, such as longitudinal method, cross-sectional method, sequential and time lag method. In other words, there are some obstacles to apply the research methods as sample not being representative. In some cases there is difficulty in establishing rapport with the subject and yet in certain other cases, the methodology used is not appropriate and thus the accuracy of data becomes questionable. In some cases the ethical aspects of research create difficulty in getting the subject to cooperate and the researcher to collect the data.
Concept of Develoment, Growth and Development, Life Span Perspective, Methods of Studying Development and Characteristics of Development
Prenatal, Infancy and Early Childhood
1.10 UNIT END QUESTIONS
What is life span development?
Explain characteristics of development.
What are major issues involved in the process of development?
Describe significant facts about development.
What are the different periods of development?
What are the various domains of human development?
1.11 SUGGESTED READINGS AND REFERENCES
Boyd, D. and Bee, H. (2006). Lifespan Development (4th ed.). Upper Saddle River, NJ: Pearson.
Hurlock, Elizabeth B. (1980) Developmental Psychology: A Life-Span Approach , Mc Graw Hill company.
Hurlock, E. B. (1980). Developmental Psychology (5th^ edition) Tata McGraw- Hill Publishing Company Ltd.
References
Amborn S.R. (1975) Child Development, Rinehart Press/Holt, Rinehart and Winson, San Fransico
Baltes, P. B., Reese, H. and Lipsett, L. (1980) ‘Lifespan developmental psychology’, Annual Review of Pyschology 31: 65 - 110.
Mussen, P. H, Conger, J.J & et.al (1984) Child Development and Personality (6th edition) Harper & Row, Publishers, New York
Rutter, M. and Rutter, M. (1992) Developing Minds. Challenge and continuity across the life span , London: Penguin.
Some portion has taken from Mamta Sharma (B.A. course 2, block 1, unit 1.) and Varsha Godbole (B.A. course 9, group I, block 2, unit 1), IGNOU course materials (2010) New Delhi.
Smith, M. (2009) Life span development and lifelong learning
Tennant, M. and Pogson, P. (1995) Learning and Change in the Adult Years , San Fransisco: Jossey-Bass. Provides a very helpful overview of life course development for those concerned with lifelong learning.
WGBH Educational Foundation (2001) Life span development our amazing capacity for change.
1.12 ANSWERS TO SELF ASSESSMENT
QUESTIONS
True or False
- True, 2) True, 3) True, 4) False, 5) False, 6) False. 7) True, 8) True.
UNIT 2 PRENATAL DEVELOPMENT
( GENETICS, ENVIORNMENT
INFLUENCE AND HAZARDS OF
DEVELOPMENT )
Structure
2.0 Introduction
2.1 Objectives
2.2 Beginnings of the Life
2.3 Characteristics of Prenatal Period
2.4 Period of Prenatal Development 2.4.1 Period of Zygote 2.4.2 Period of Embryo 2.4.3 Period of Fetus
2.5 Environmental Influences
2.6 Let Us Sum Up
2.7 Unit End Questions
2.8 Suggested Readings and References
2.9 Answers to Self Assessment Questions
2.0 INTRODUCTION
Prenatal development is the process in which an embryo or fetus, gestates during preganancy, from fertilisation until birth. Often, the terms fetal development, foetal development are used in a similar sense.Most physiologists and members of the medical profession believed that most development takes place before birth. Development before birth takes place in three stages or period’s i.e. ovum, embryo and fetus. Many factors are considered to understand the behaviour of a developing child. Mainly five factors are considered:
Genetically determined biological variables
Nongenetically determined biological variables (i.e., lack of oxygen during the birth process and malnutrition)
The child’s past learning
The immediate socio psychological environment (parents, siblings, peers and teachers)
The social and cultural milieu in which the child develops.
We always considered biological and environment separately for ease of exposition but they always act in unison. This is as true of the individual cell as it is of the whole person. The science of genetics and embryology has shown dramatic progress during the last 25 years. This unit will deal with the current knowledge of human genetics 2 0 and prenatal factors affecting the course of development. In this unit you will be able
to understand the major happenings during the nine months of prenatal developement and what genetics, environmental influence and hazards affect the course of development.
2.1 OBJECTIVES
After going through this unit, you will be able to:
z explain the concept and characteristics of the prenatal period;
z describe the stages of prenatal period ;
z point out the genetic factors;
z describe the attitudes of significant people towards the child; and
z analyse the common physical hazards in each subdivision of the prenatal period.
2.2 BEGINNINGS OF THE LIFE
The new life begins with the combination of a male sex cell and female sex cell. The development of each individual begins when a sperm cell from the male penetrates the wall of an ovum, or egg, from the mother. These sex cells are developed in the reproductive organs. For example, the male sex cells are produced in the male gonads, the testes, while the female’s sex cells are produced in the female gonads, the ovaries. Development begins at conception. At the moment that the tiny Tadpole- shaped sperm penetrates the wall of the ovum, it releases 23 minute particles called chromosomes. At approximately the same time, the nucleus, the inner core of the ovum, breaks up, releasing 23 chromosomes of its own, so that the new individual begins life with 46 chromosomes.
All the child’s biological heritage from the father and mother is contained in these 23 pairs of chromosomes. Of these pairs, 22 are autosomes, possessed equally by males and females. The 23 pair, the sex chromosomes, differs in males and females. It is these chromosomes that determine a child’s sex. A female will have two X chromosomes (XX), while a male has an X and Y chromosomes (XY).
Male and female sex cells also differ in two important ways. First, in the mature ovum there are 23 matched chromosomes while in the mature spermatozoa there are 22 matched chromosomes and one unmatched chromosome which may be either an X or a Y chromosomes. The X and Y chromosomes are the sex determinant chromosomes. The mature chromosome ovum always contains an X chromosome. If it is fertilised by a Y-bearing spermatozoa, the offspring will be a boy. If it is fertilised by an X-bearing spermatozoa, the offspring will be a girl.
Once the male and female cells have united, nothing can be done to change the sex of the newly formed individual. Whether this individual is male or female has a lifelong effect on the individual’s patterns of behaviour and personality. The question arises why the sex of an individual is important to lifelong development. The answer of this question consists of three points, viz. the following:
i) Each year children come under increasing cultural pressure from parents, teachers, their peer group and society at large to develop attitudes and behaviour patterns that are considered appropriate for members of their sex. Children who learn to behave in ways that are considered appropriate for their sex are assured of social acceptance.
Prenatal Development ( Genetics, Enviornment Influence and Hazards of Development )
2 3
z At the time of conception, the sex of the baby is fixed. Except when surgery is used for sex transformation, the sex of the individual, determined at the time of conception, remains the same and does not change.
z During the prenatal period, proportionally greater growth and development take place than any other time throughout the entire life of human.
z Before birth (during nine month) the child grows from microscopically small cell to an infant who measures approximately twenty inches in length and weight, on the average 7 pounds. It is observed that during this time weight increases 11 million times.
z Many believe that this time is more hazardous than other periods of the life span. It certainly is a time when environment or psychological hazards can have marked effect on the pattern of later development..
z During the prenatal period, the attitudes of people towards the newly created individual has significant impact on the development. For example the mother’s positive attitude is essential to the normal development of the newly created individual.
2.4 PERIODS OF PRENATAL DEVELOPMENT
The prenatal period is ten lunar months of twenty-eight days each in length or nine calendar months. However, the period can and does vary greatly in length, ranging from 180-334 days. There are approximately three times as many babies born prematurely as post maturely. Meredith has reported that the average length of the prenatal period is 38 weeks or 266 days. However, 70% of babies vary from 36 to 40 weeks or 266 days and 98% range from 34 to 42 weeks (238-294 days). The prenatal period is divided into three stages. These are (i) period of the zygot (ii) period of the embryo and (iii) period of the fetus. Let us take up each of these in detail.
2.4.1 Period of Zygote ( fertilisation to end of second week )
Half of a person’s genetic material comes from his father and half comes from the mother. These two halves come together to form a unique combination of genetic potentialities when the sperm fertilises the egg. In the nucleus of the fertilised egg, or zygote, are the materials that bear the pattern for a new person, one who is different from his parents and yet like them. This first cell in which the male genes are joined with the female is called the Zygote. The zygote looks like an unfertilised egg. The egg is so much larger than the sperm that it can absorb the sperm without showing it. However, the unfertilised egg has only twenty-three chromosomes, whereas the zygote has forty six –the twenty three that were in the egg originally and the additional twenty three contributed by the male. Less than two days after the sperm unites with the egg, the zygote divides into two cells. Then these two cells each divide again, and the process of division goes on, forming in nine months a new human being.
2.4.2 Period of Embryo ( end of the second week to end of the
second lunar month )
The embryo develops into a miniature human being. This stage begins on the 15th day after conception and continues until about the 8th week, or until the embryo is 1.2 inches in length. During this period the cells of the embryo are not only multiplying, but they are taking on specific functions. This process is called tissue differentiation. It is during this critical period of differentiation (most of the first trimester or three-
Prenatal Development ( Genetics, Enviornment Influence and Hazards of Development )
Prenatal, Infancy and Early Childhood
month period) that the growing fetus is most susceptible to damage from external sources (teratogens) including viral infections such as rubella, x-rays and other radiation, and poor nutrition.
A child who has one developmental problem may have other problems that arose at the same time. Kidney problems and hearing problems, for example, are often found together because both kidneys and the inner ears develop at the same time. Formation of the heart begins in 3 weeks, the beginning development of the brain and spinal cord, and the beginning of the gastrointestinal tract.
Teratogens introduced during this period may cause severe problems such as the absence of one or more limbs or a heart that is outside of the chest cavity at birth.
Beginnings of the vertebra, the lower jaw, the larynx (voice box), and the rudiments of the ear and eye develop at weeks 4 and 5 (1/4 inch long). The heart, which is still outside the body, now beats at a regular rhythm. Although arm and leg “buds” are visible with hand and foot “pads”, the embryo still has a tail and cannot be distinguished from pig, rabbit, elephant, or chick embryo by an untrained eye.
Teratogens may cause very serious problems involving the esophagus, vertebrae, and eyes. The baby could be born with severe facial clefts or missing hands or feet.
At week 6 (1/2 inch, 1/1000 of an ounce), formation of the nose, jaw, palate, lung buds takes place. The fingers and toes form, but may still be webbed. The tail is receding, and the heart is almost fully developed. Teratogens at this point may leave the baby with profound heart problems or a cleft lip.
In the 7th^ week (7/8 inch, 1/30 ounce) eyes move forward on the face, and the eyelids and tongue begin to form. All essential organs have begun to form. Teratogens may cause heart and lung problems, a cleft palate, and ambiguous genitalia (not quite male or female).
At the 8th^ week (1 inch, 1/15 ounce) embryo now resembles a human being. The facial features continue to develop and the external ear appears. Also, we see the beginnings of external genitalia. By now, the circulation through the umbilical cord is well developed. The long bones begin to form and the muscles are able to contract. Teratogens may still cause heart problems and stunting of the fingers and toes
2.4.3 Period of Fetus (end of the second lunar month to birth)
At this point the embryo is developed enough to call a fetus. All organs and structures found in a full-term newborn are present. The head comprises nearly half of the fetus’ size and the face is well formed at weeks 9 to 12 (3 inches, 1 ounce). The eyelids close now and will not reopen until about the 28th week. The tooth buds for the baby teeth appear. The genitalia are now clearly male or female.
Weeks 13 to 16 (6 inches) mark the beginning of the second trimester. Although the skin of the fetus is almost transparent, fine hair develops on the head called lanugo. The fetus makes active movements, including sucking, which leads to some swallowing of the amniotic fluid. A thin dark substance called meconium is made in the intestinal tract. The heart beats120-150 beats per minute and brain waves are detectable.
Eyebrows and lashes appear and nails appear on fingers and toes at week 17 to 20 (8 inches). This is an exciting time for the parents: The mother can feel the fetus moving (quickening) and also hear the heartbeat with the help of stethoscope.
