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Lesson 14: Stages of Human Development

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I. PRE-NATAL STAGE (Conception to Birth)

Picture from VeryWell Mind

• Involves tremendous growth - from a single cell to an organism complete with brain and behavioral capabilities
• Age when heredity endowments and sex are fixed and all body features, both external and internal, are developed.

Pre-natal stage

• Relating to pregnant woman and her unborn baby,
• before birth; during or relating to pregnancy.

The pre‑natal stage is the period from conception to birth. During this time, the baby develops rapidly, starting from a single cell and forming into a complete human being with organs, body systems, and basic structures. It is also the stage when heredity traits and sex are determined. Both external features, such as arms and legs, and internal features, such as the heart and brain, are formed. The term pre‑natal simply refers to the stage of development before birth.

THREE PERIODS OF PRE-NATAL STAGE:

1. GERMINAL PERIOD

• prenatal development that takes place in the first two weeks after conception.
• It includes the creation of the ZYGOTE, continued cell division and the attachment of the zygote to the uterine wall.

Inner and Outer layers of the organism

Image from InstitutoBernabeu

A. BLASTOCYST

• inner layer of cells.
• develops later into the embryo

B. TROPHOBLAST

• outer layer of cells.
• provides nutrition and support for the embryo

The germinal period is the very first stage of prenatal development, lasting about two weeks after conception. During this time, the fertilized egg, called a zygote, begins rapid cell division and makes its way to the uterus. Once it reaches the uterine wall, it attaches itself firmly, which is an important step for further development. At this stage, two main layers of cells form: the blastocyst, which is the inner layer that will later develop into the embryo, and the trophoblast, which is the outer layer that provides nutrition and support for the growing organism. 

2. EMBRYONIC PERIOD

• prenatal development occurs 2 to 8 weeks after conception.
• the zygote will become EMBRYO

The following development takes place:

cell differentiation intensifies

Three layers of cells

ENDODERM

• inner layer of the cell
• Becomes the digestive and respiratory systems

ECTODERM

• outermost layer of the cell
• becomes the nervous, sensory receptors and skin parts.

MESODERM

• middle layer
• develops into circulatory, skeletal, muscular, excretory, and reproductive system.

Life-support systems for the embryo develop

Three life-support systems

PLACENTA

• a life support system that consists of disk-shaped group of tissues in which small blood vessels from the mother and the offspring intertwine but do not join.

UMBILICAL CORD

• contains two arteries and one vein that connects the baby to the placenta.

AMNION

• is a bag or an envelope that contains a clear fluid in which the developing embryo floats.

Organs appear

ORGANOGENESIS

• It is the process of organ formation during the first two months of prenatal development

The embryonic period takes place from the 2nd to the 8th week after conception, when the zygote develops into an embryo. During this stage, cell differentiation becomes more intense, and three distinct layers of cells form. The endoderm, or inner layer, develops into the digestive and respiratory systems. The ectoderm, which is the outer layer, forms the nervous system, sensory organs, and skin parts. The mesoderm, or middle layer, develops into the circulatory, skeletal, muscular, excretory, and reproductive systems. Alongside these changes, life‑support systems for the embryo also develop. The placenta allows the exchange of nutrients and waste between mother and child without their blood mixing, while the umbilical cord connects the embryo to the placenta with two arteries and one vein. The amnion is a protective sac filled with fluid where the embryo floats safely. By the end of this stage, organogenesis, or the formation of organs, begins, making the embryonic period a critical foundation for later growth and development.

3. FETAL PERIOD

• last from about 2 months after conception until 9 months when the infant is born.
• dramatic course and organ systems mature to the point at which life can be sustained outside of the womb.

The fetal period begins about two months after conception and continues until birth, lasting roughly nine months. During this stage, the developing baby is now called a fetus, and the focus shifts from forming new structures to the growth and maturation of organs and body systems. The fetus undergoes rapid physical changes, increasing in size and weight, while the brain, lungs, and other vital organs continue to develop. By the later months, these organs mature enough to sustain life outside the womb, which is why premature babies born after this stage may survive with medical support. 

II. INFANCY (birth to 2 weeks)

• Shortest of all developmental periods
• Infants - suggests extreme helplessness

Subdivisions of Infancy

a. Period of the Partunate or from the time the fetal body has emerged from the mother's body and lasts until the umbilical cord has been cut and tied.

b. Period of the Neonate or from the cutting and tying of the umbilical cord to the end of second week of the postnatal life.

The infancy stage, which lasts from birth to about two weeks, is considered the shortest of all developmental periods. At this stage, the infant is extremely helpless and fully dependent on others for survival and care. Infancy is further divided into two parts. The period of the partunate begins the moment the baby emerges from the mother’s body and continues until the umbilical cord is cut and tied. After this, the period of the neonate begins, lasting from the cutting of the cord until the end of the second week of life.

III. BABYHOOD STAGE  (2 weeks to 2 years)

• Characterized by decreasing dependency for the reason that this is the time when babies achieve enough body control to become independent.
• Babyhood skills: hand skills and leg skills
• Crying, cooing, babbling, gesturing, and emotional expressions are examples of pre-speech forms of communication.
• Babies are capable of establishing friendships

The babyhood stage, which lasts from about two weeks to two years, is marked by a gradual decrease in dependency as babies begin to gain control over their bodies. During this period, they develop important hand and leg skills, such as grasping objects, crawling, and eventually walking, which allow them to explore their surroundings more independently. Communication also begins to take shape through pre‑speech forms like crying, cooing, babbling, gesturing, and showing emotions, all of which prepare the child for actual speech later on. This stage is also when babies start to form simple social connections, showing that they are capable of establishing early friendships and bonds with others. 

IV. EARLY CHILDHOOD (3 to 5 years old)

• "the" preschooler years"
• Years before formal schooling begins.
• Pre-gang, exploratory, and questioning age, when language and elementary reasoning are acquired and initial socialization is experienced.

Developmental Tasks for Infancy & Early childhood

• Learning to walk.
• Learning to crawl.
• Learning to take solid food.
• Learning to talk.
• Learning to control the elimination of body wastes.
• Learning sex differences and sexual modesty.
• Getting ready to read.
• Forming concepts and learning language to describe social and physical reality.

The early childhood stage, which covers ages 3 to 5, is often called the preschool years because it comes just before formal schooling begins. This period is sometimes described as the pre‑gang, exploratory, and questioning age, since children are naturally curious, eager to explore their surroundings, and begin asking many questions about the world. During this stage, language skills expand rapidly, and children start to develop elementary reasoning abilities, allowing them to express ideas and understand simple concepts. Socialization also begins, as children learn to interact with peers and adults outside the family. The developmental tasks for infancy and early childhood include learning to walk, crawl, eat solid food, talk, and control the elimination of body wastes. Children also begin to recognize sex differences, develop a sense of modesty, prepare for reading, and form concepts that help them describe both social and physical reality.

V. MIDDLE AND LATE CHILDHOOD (6-12 years)

• Gang and creativity age when self-help skills, social skills, school skills and play skills are developed.
• The fundamental skills of reading, writing and arithmetic are mastered.
• The child is formally exposed to the larger world and its culture. ~ formal education
• Achievement becomes a more central theme of the child's world and self-control increases.

Developmental Tasks for Middle and Late childhood

• Learning physical skills necessary for ordinary games.
• Learning to get along with age mates.
• Building wholesome attitudes toward oneself as a growing organism.
• Learning an appropriate masculine or feminine social role.
• Developing concepts necessary for everyday living.
• Developing conscience, morality and a scale of values.
• Achieving personal independence.
• Developing attitudes toward social groups and institutions.

The middle and late childhood stage, which covers ages 6 to 12, is often called the gang and creativity age because children begin to form peer groups and show greater independence in their activities. During this time, they develop important self‑help, social, school, and play skills, while also mastering the fundamental academic skills of reading, writing, and arithmetic. Formal education plays a major role, as children are now exposed to the larger world and its culture. Achievement becomes a central theme in their lives, and they begin to show more self‑control in their behavior. Developmental tasks at this stage include learning physical skills for games, getting along with peers, building a healthy self‑image, and learning appropriate gender roles. Children also develop concepts needed for everyday living, form a conscience and moral values, strive for personal independence, and build attitudes toward social groups and institutions. 

VI. ADOLESCENCE (13-18 yrs)

• Transition age from childhood to adulthood
• Begins with rapid physical changes - dramatic gains in height and weight, changes in body contour, and the development of sexual characteristics such as enlargement of breasts, development of pubic and facial hair, and deepening voice.
• Pursuit of independence and identity are prominent
• Thought is more logical, abstract and idealistic. More time spent outside of the family.

Developmental Tasks for Adolescence Stage

• Achieving new and more mature relations with age mates of both sexes.
• Achieving a masculine or feminine social role.
• Accepting one's physique and using the body effectively.
• Achieving emotional independence of parents and other adults.
• Preparing for marriage and family life.
• Acquiring a set of values and an ethical system as a guide to behavior.
• Desiring and achieving socially responsible behavior.

The adolescence stage, which spans from ages 13 to 18, is a transition period from childhood to adulthood. It begins with rapid physical changes, including noticeable gains in height and weight, changes in body shape, and the development of sexual characteristics such as breast enlargement in girls, the growth of pubic and facial hair, and a deepening of the voice in boys. Beyond physical growth, this stage is marked by the pursuit of independence and identity, as adolescents begin to explore who they are and how they fit into society. Their thinking also becomes more logical, abstract, and idealistic, allowing them to reason about complex issues and imagine possibilities for the future. Socially, they spend more time outside the family, forming stronger peer relationships and testing their independence. Developmental tasks during this stage include building mature relationships with peers of both sexes, accepting and using one’s body effectively, achieving emotional independence from parents, and preparing for adult roles such as marriage and family life. Adolescents also work toward developing a personal value system, striving for socially responsible behavior, and establishing a clearer sense of identity.

VII. EARLY ADULTHOOD (19-29 yrs)

• Age of adjustment to new patterns of life and new roles such as spouse, parent, and bread winner.
• It is a time of establishing personal and economic independence, career development, selecting a mate, learning to live with someone in intimate way, starting a family and rearing children.

Developmental Tasks of Early Adulthood

• Selecting a mate.
• Learning to live with a partner.
• Starting family.
• Rearing children.
• Managing home.
• Getting started in occupation.
• Taking on civic responsibility.
• Finding a congenial social group.

The early adulthood stage, which spans from ages 19 to 29, is often described as a period of adjustment to new patterns of life and responsibilities. At this stage, individuals begin to establish personal and economic independence, while also taking on important roles such as spouse, parent, and breadwinner. Career development becomes a major focus, along with the challenge of selecting a life partner and learning to live with someone in an intimate and committed way. Many also start families, rear children, and manage their own households, which requires balancing personal, family, and work responsibilities. Developmental tasks during this stage include selecting a mate, raising children, managing a home, beginning an occupation, taking on civic responsibilities, and finding a congenial social group.

VIII. MIDDLE ADULTHOOD (30-60 yrs)

• Transition age when adjustments to initial physical and mental decline are experienced.
• It is a time of expanding personal and social involvement and responsibility; of assisting the next generation in becoming competent and mature individuals; and of reaching and maintaining satisfaction in career.

Developmental Tasks of Middle Age

• Assisting teenage children to become responsible and happy adults.
• Achieving adult social and civic responsibility.
• Reaching and maintaining satisfactory performance in one's occupational career.
• Developing adult leisure time activities.
• Relating oneself to one's spouse as a person.
• To accept and adjust to the physiological changes of middle age.
• Adjusting to aging parents.

The middle adulthood stage, which spans from ages 30 to 60, is often described as a transition age because individuals begin to experience the first signs of physical and mental decline. Despite these changes, it is also a period of growth in terms of personal and social involvement, as people take on greater responsibilities in their families, careers, and communities. Many adults in this stage focus on guiding the next generation, helping their teenage children become responsible and well‑adjusted individuals. Career satisfaction and maintaining good performance at work are also central concerns, along with developing meaningful leisure activities that provide balance and fulfillment. Other important developmental tasks include strengthening the marital relationship, adjusting to the natural physiological changes of aging, and caring for or supporting aging parents.

IX. LATE ADULTHOOD (61 yrs and above)

• It is a time for adjustment to decreasing strength and health, life review, retirement, and adjustment to new social roles.
• Retirement age when increasingly rapid physical and mental decline are experienced.

Developmental Tasks of Later maturity or Old Age

• Adjusting to decreasing physical strength and health.
• Adjusting to retirement and reduced income.
• Adjusting to death of a spouse.
• Establishing an explicit affiliation with one's age group.
• Adopting and adapting social roles in a flexible way.
• Establishing satisfactory physical living arrangements.

The late adulthood stage, beginning at around age 61 and above, is a period marked by significant adjustments in many areas of life. During this stage, individuals often face the reality of declining physical strength and health, which requires adapting to new limitations. It is also the time of retirement, when people must adjust to reduced income and a change in daily routines. Emotional challenges may arise, such as coping with the death of a spouse or close peers, which can affect one’s sense of stability and belonging. At the same time, older adults work on establishing stronger connections with their age group, adopting social roles in flexible ways, and finding satisfaction in their living arrangements.

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