HUMAN DEVELOPMENT
PRENATAL DEVELOPMENT
Prenatal / antenatal period of gestation refers to foetal development over the period of
pregnancy from conception to parturition [childbirth].
THREE STAGES OF PRENATAL DEVELOPMENT
Germinal stage
Introduces the first two weeks of gestation, which start w. conception and end w.
implantation on the uterine wall.
Cell partition initiates during the first 24 – 36 hours after conception. The cells are all similar
until about 4 days after impregnation; they resemble a hollow sphere w. two outer layers and
are called a blastocyst.
On day , the blastocyst comes into connection w. the uterine wall and by day 12 it is
completely buried in the uterine wall, a mechanism called implantation. The external cells
insert in the uterine wall between 10 days and two weeks after impregnation.
Several of the cells of the blastocyst’s wall merge w. uterine coating cells to begin
constructing the placenta, an appendage that permits oxygen, nutrients, and other
elements to travel between the mother’s and the baby’s blood. The placenta imports the
mother’s and baby’s blood alongside one another, without permitting them to mix.
The blastocyst’s internal cells start to concentrate themselves in a specific area. The cluster of
cells that attaches the embryo to the placenta will become the umbilical cord. Alternative
cells shape the yolk sac, a formation that will manufacture blood cells until the embryo’s
blood-cell-producing organs are configured. More grow to become the amnion, a fluid-filled
pouch in which the infant will drift until just before birth. By the 12th day, the cells that will turn
out to be the embryo’s anatomy are in position.
Embryonic stage
Commences when implantation has been achieved.
Two weeks to two months [week eight].
The embryo’s cells start to concentrate to shape the basics of all the body’s organs.
By the third week after impregnation, the cells of the nervous system [neurons] shape a
construction called the neural tube, from which the brain and the spinal cord will grow. A
primordial heart and the precursor of the kidneys evolve in week three, along w. three
pouches that will develop into the digestive system.
In week four, the end of the neural tube proliferates to form the brain. Spots that will grow to
be the eyes emerge and the and the hear begins to throb. The spinal column and ribs grow
to be noticeable, as bone and muscle cells shift into place. The face starts to obtain form
and the endocrine system begins to grow.
The length of the embryo is around 6 – 10mm in length in the fifth week. The arms and legs
are growing quickly. The eyes contain corneas and lenses, and its lungs are starting to
enlarge.
In week six, the embryos brain begins to create electrical activity and it moves in reaction to
stimulation. The genitalia enlarge in week six.
During week seven, embryos begin to move instinctively. They have observable skeletons
and fully developed limbs. The bones are starting to become firm, and the muscles are
growing. The eyelids close to guard the evolving eyes, and the ears are entirely shaped.
During the week eight, the liver and spleen begin to work so that the embryo can create
and filter its own blood cells. Its heart is well developed, and the links between the brain and
the rest of the body are well established. Its digestive and urinary systems are performing.
Organogenesis [organ growth] is complete by the end of week eight.
,Foetal stage
The closing phase that lasts about seven months.
Two months to birth.
Foetus grows in weight from approx. 113g to approx. .5kg and its length expands from
25mm to about 500mm. The foetal period includes the procedure of cultivating and finishing
all the primitive organ systems.
The capability to live outside the uterus is known as viability. This usually occurs at the end of
week 24.
FACTORS THAT INFLUENCE PRENATAL DEVELOPMENT
Genetic disorders
Two types:
Gene abnormalities: The consequence of defective genes.
Defective genes would affect the way a foetus develops.
These faulty genes are transmitted from one generation to the next,
the main afflicted family member that draws clinical attention to the
disorder is called a proband.
Example: spinal bifida; an ethnically linked gene abnormality, neural
tube doesn’t close properly.
Chromosome abnormality: A segment of chromosomal DNA that is irregular.
Will result in a disorder or will affect the way a baby looks.
Example: down-syndrome [/trisomy-21]; extra chromosome at
the 21st pair.
Maternal nutrition
Performs vital role in perinatal growth.
Sufficient quantities of particular nutrients, such as folic acid, are required for neural tube
growth; inadequate quantities are linked to illnesses such as type two diabetes mellitus.
The overall total number of calories is critical to good prenatal development of nervous
system.
Nutriment [growth-promoting agents] accessibility builds upon the quality and magnitude of
the maternal reservoir and her metabolic competency to create a nutrient rich environment
for various phases of growth.
Maternal stress and emotion
There is a correlation between the high levels of stress hormones [epinephrine,
norepinephrine, and adreno-corticotropic hormone] in the foetal blood stream and
maternal stress.
Compared to mothers w. low anxiety levels, mothers w. high levels of anxiety are more likely
to have babies who are hyperactive, irritable, have low birth weight and experience
problems w. feeding and sleeping. Other effects correlated w. maternal stress during
gestation include the child having a depressed immune response, w. increased vulnerability
to infectious diseases, slow motor development and sub-average cognitive development.
Maternal drug use
Alcohol:
Alcohol use in the perinatal period is the main source of severe mental and physical
deficiencies in children.
Foetal Alcohol Syndrome [FAS] is characterized by the developmental delay of foetal origin
[height and weight], microphthalmia [small eyeballs], tiny palpebra fissures, mid-face
hypoplasia [underdevelopment], a flat / short philtrum [a vertical groove in the middle area
of the upper lip] and a thin upper lip. Central nervous system indicators consist of
microcephaly [head circumference beneath the third percentile], a history of delayed
development, hyperactivity, attention deficits, learning disabilities, intellectual disabilities and
seizures.
,Smoking:
Infants of mothers who smoke are on average about 227g lighter at birth than infants of non-
smoking mothers. Smoking throughout the perinatal period is associated w. below-average
infant birth weight and / or premature births. Babies born to mothers who smoked during
pregnancy are at greater risk for long-term consequences, such as learning problems, anti-
social behaviour and attention deficit hyperactivity disorder [ADHD].
Other substances:
Two most widespread illegitimate drugs abused by pregnant women are marijuana and
cocaine. Marijuana exposure is associated w. infants presenting low birth weight, early birth,
withdrawal-like symptoms, extreme crying, tremors and hyperemesis [severe and chronic
vomiting].
In terms of cocaine usage in pregnancy, babies have shown behaviour abnormalities such
as increased irritability, crying and diminished desire for human interaction. Babies of mothers
hooked on narcotics during perinatal period go through withdrawal syndrome at birth.
Prescriptions and over-the-counter drugs:
Prenatal exposure to countless numbers of medications can result in foetal abnormalities.
Frequently used drugs that could cause embryonic / foetal malformations include antibiotics
[tetracyclines], anticonvulsants [valproate], carbamazepine [Tegretol], phenytoin,
progesterone-oestrogens, lithium and warfarin.
Maternal illness and psychopathology
Many illnesses pose high risk for damaging brain development which can lead to intellectual
and other disorders: rubella, syphilis, cytomegalic inclusion disease, toxoplasmosis, AIDS,
mumps, genital herpes and severe flu.
The influence of culture, family and environmental toxins
Culture influences thoughts and decision around pregnancy and child-rearing.
Example: not breastfeeding / being able to breastfeed may cause the mother to feel guilt
and shame.
Example: miscarriage / illness during pregnancy could be that the ancestors have turned
their backs on the pregnant women and her family for not having observed certain cultural
practices.
Changes in family structure and the roles and responsibilities in the home: single-parent
families, poor access to social and / or familial support, child-headed households, and
female-headed households.
Environmental toxins that can affect the developing foetus include air pollution, radioactivity,
etc. Prenatal exposure to air pollution is linked to cognitive deficits by age five and obesity by
age seven. Contact w. unsafe levels of radioactivity, specifically between weeks two and
fifteen of pregnancy, increases the child’s vulnerability to developing crude malformations,
inhibition of physical growth, having unusual brain functions and / or heightened
susceptibility to developing cancer.
MOTOR, LANGUAGE AND SOCIO-EMOTIONAL DEVELOPMENT IN CHILDHOOD
BASIC PRINCIPLES
Motor development refers to the progression of muscular coordination required for physical
activities.
Cephalocaudal trend: head-to-foot motor development. Children tend to gain control over
the upper part of their bodies before the lower part. Infant learns to crawl.
Proximodistal trend: centre-outward tendency adopted during motor development. Children
gain control over their torso before their extremities.
Developmental norms: average age at which abilities and behaviours are shown. Can be
used as benchmarks.
, Cultural variations: rapid vs slow motor development. Rapid has been observed in cultures
that provide special practice in basic motor skills and slow has been observed in some
cultures that discourage motor exploration.
EMOTIONAL DEVELOPMENT: TEMPERAMENT
Temperament: characteristics of mood, activity level and emotional reactivity.
Some babies cheerful while others are irritable.
Alexander Thomas and Stella Chess conducted study on development of temperament.
They identified three basic styles of temperament in children.
- Easy [40%]:
o Happy. o Regular in sleep and
o Adaptable. eating.
o Not readily upset.
- Slow-to-warm-up [15%]:
o Less cheery. o Slower in adapting to
o Less regular in sleep and change.
eating. o Reactions aren’t as intense.
- Difficult [10%]:
o Glum / crying. o Relatively irritable.
o Erratic in sleep and eating. o Inflexible.
o Resistant to change.
Rest of children [35%] displayed fusion of three temperaments.
EMOTIONAL DEVELOPMENT: ATTACHMENT
Attachment: the close, emotional bonds of affection that develop between infants and their
caregivers.
Child’s first attachment usually occurs w. mother because in many cultures, she is the primary
caregiver, especially in early years of life.
Infant attachment to mothers is not instant. By about 6 – 8 months, infants begin to show a
pronounced preference for their mothers’ company and often protest when separated from
her.
Separation anxiety: emotional distress seen in many infants when they are separated from
people w. whom they have formed an attachment.
This type of anxiety peaks around 14 – 18 months,
Theory of attachment
Put forward by John Bowlby.
He was influenced by ethological theory, which proposed that attachment was an
evolutionary mechanism to ensure the survival of the vulnerable and dependent infant. He
argued that infants and their primary carers are biologically predisposed to form
attachments. Infants are born w. the ability to elicit attachment behaviour from carers, and
carers [usually, but not always the mother] are biologically programmed to respond. Early
infant behaviours [including reflexes such as crying] and, later, proximity-seeking behaviours
are therefore designed to keep carer nearby and attentive to child’s needs. In this way, the
infant’s chance of physical survival is maximized.
Patterns of attachment
Research by Mary Ainsworth and colleagues.
Showed infant-mother attachments vary in quality.
Ainsworth used method called the strange situation procedure, in which infants are exposed
to a series of eight separation and reunion episodes to assess the quality of their attachment.
The three-minute episodes involve various scenarios w. / without a parent and / or stranger in
the room. The child’s reaction [distress / comfort] to parent’s departures and returns are
carefully monitored to gauge attachment quality.
Ainsworth found that attachments fall unto three categories: secure attachment, avoidant
attachment, and anxious-ambivalent attachment.
