Human Development: From Conception to Infancy
Cephalocaudal and Proximodistal Principles
Cephalocaudal principle
Head to tail
Development proceeds from the head to the trunk.
Proximodistal principle
Near to far
Development proceeds from the center of the body out.
Prenatal Development Stages
GERMINAL STAGE
Fertilization to 2 weeks
Zygote divides, becomes more complex
Moves through fallopian tube to uterus
Now a blastocyst
Implants into uterine wall around 6th day
Three layers of cells cluster:
- Ectoderm
Skin, nails, hair, teeth, sensory organs, nervous system - Endoderm
Digestive system, liver, pancreas, salivary glands, respiratory system - Mesoderm
Inner layer of skin, muscles, skeleton, excretory and circulatory systems
EMBRIONIC STAGE
2 to 8 weeks
Organogenesis
Organs and body systems develop rapidly
Most vulnerable stage
Most miscarriages happen during the first trimester
FETAL STAGE
8 weeks to birth
Rapid growth – 20x its previous length
“Finishing touches” – fingernails, toenails, eyelids
Movement, swallow, hiccup, suck their thumbs
Individual differences – boys tend to be more active
Taste and smell
Hearing
Learning and memory
Environmental Influences on Development
ENVIRONMENTAL INFLUENCES
Teratogen
Interferes with development
Examples: viruses, drugs, radiation
Maternal weight
Gain about 16 to 40lbs, depends on person
Less likely to have complications
Nutrition
Omega-3
DHA
Folic acid (B vitamin)
Malnutrition
Smaller birth weight, infant mortality, birth complications
Outcomes for child: stunted growth, psychopathology later in life, diabetes
Medical drugs
Nicotine, Alcohol, Caffeine, Illnesses, Stress, anxiety, and depression
Air pollution, Extreme heat
Radiation (x-rays), nuclear disasters
Maternal and Paternal Factors
MATERNAL AGE
History-graded influence
Fertility treatments
Shifting norms
With advanced age
Higher chance of miscarriage
More likely to experience complications
Premature delivery
With younger age (e.g., teens)
More likely to have premature or underweight babies
Heightened risk of infant death
Access to prenatal care
PATERNAL FACTORS
Sperm can be impacted by exposure to lead, nicotine, marijuana, alcohol, radiation
Can affect birth weight and fetal growth
Age
Damaged or deteriorated sperm
Risk of rare conditions
Genetics and Heredity
GENETICS
PHENOTYPE: Observable characteristics
Product of underlying genetic makeup
GENOTYPE: Underlying genetic makeup
The recipe for you!
CHROMOSOMES
23 matching pairs
Except the XY pair in males
Made up of deoxyribonucleic acid (DNA)
Ladder
Each rung = base pairs
Forms sequence
Genetic instructions
Gene
Segment of DNA along the length of chromosome
21,000 protein-coding genes
18,000 regulator genes
SEX CELLS
Gametes
Sperm
Ovum
Contain 23 chromosomes
Conception
Sperm and ovum unite
Form zygote
46 chromosomes
CHROMOSOMAL ABNORMALITIES
Result from mistakes during meiosis when the ovum and sperm are formed
Down syndrome (trisomy 21)
MULTIPLE OFFSPRING
Fraternal (dizygotic) twins
Release and fertilization of two ova
No more alike than two siblings
Identical (monozygotic) twins
Zygote separates into two clusters
Develops into two individuals
HOMOZYGOUS
Child receives similar alleles from both parents
Child will display the inherited trait
HETEROZYGOUS
Child receives different alleles from parents
The relationship between the two alleles will influence the phenotype
DOMINANT RECESIVE PATTERN
Only one allele determines the child’s characteristics
Dominant allele
Has effect on phenotype
Recessive allele
No effect
Presence in genotype means child is a carrier of the trait
Contextual Factors
CHRONOSYSTEM
Within family system
Different reactions among family members
Depends on support of other family members
Historical factors
Increased divorce rate
Low birth rate
Expanding gender roles
Acceptance of queer couples
Dual-earner families
Longer lifespan – intergenerational impacts
Protective factors
Supportive parenting
Temperament profile
Gene-Environment Correlation
GENE-ENVIRONMENT CORRELATION
Passive correlation
Parents, with similar genetics, provide environments
Evocative correlation
Child’s behavior evokes responses from the environment
These behaviors are influenced by the child’s genetics
Responses from the environment strengthen the behavior
Active correlation
Seek environments that fit genetic tendencies
With age
Epigenetics
Development resulting from interactions between heredity and environment
Chemical tags impact gene expression
Experiences impact chemical tags
Stages of Childbirth
STAGES OF A CHILDBIRTH
Dilation and effacement of the cervix
Longest stage (12-14 hours for first birth, 4-6 for later births)
Contractions become more frequent and powerful
Cervix widens and thins
Forms channel from uterus to birth canal
Delivery of the baby
Shorter
Lasting 50 minutes for first birth, 20 minutes for later births
Mother feels nature urge to push
Force baby out
Delivery of the placenta
Contractions and pushes force placenta out
10 minutes to 1 hour
Cesarean Delivery
CESAREAN DELIVERY
Surgical birth
Warranted by medical emergencies
Separation of placenta from uterus
Maternal infection
Breech position
Anoxia
“Once a cesarean always a cesarean”
Concerns
Major surgery
Anesthetic can cross placenta
Miss surge of hormones when pushed through birth canal
Newborn Characteristics
NEWBORN BABY
NEONATE
First four weeks of life
20 inches long, 7.5lbs
Lose weight and then gain again
Features
Large head – ¼ of body length
Receding chin – easier to nurse
Fontanels – bones of skull do not meet, helpful for delivery
Features
Pinkish
Lanugo – fuzzy prenatal fair
Vernix caseosa – oily protection against infection
Lungs not fully functioning by full-term birth
More susceptible to respiratory problems
Newborn Assessment
ASSESMENT
Apgar scale
One minute after delivery
Again at 5 minutes
Scoring
Score of 7 to10: good health
Score below 5 to 7: baby needs help breathing
Score below 4: baby needs lifesaving treatment
Brazelton Neonatal Behavioral Assessment Scale (NBAS)
Neurological and behavioral test
Measure responses to the environment
Up to 2 months old
Assesses
Motor organization
Reflexes
State changes
Attention and interactive capacities
Central nervous system instability
Low Birth Weight and Postmaturity
LOW BIRTH WEIGHT
Neonates weigh less than 5lbs at birth
Babies born more than 3 weeks early (before 37th/40 weeks of gestation)
Small-for-date infants are smaller than 90% of babies of same gestational age
POSTMATURITY
5.5% of births in the U.S.
Postterm neonates are long and thin
Kept growing without adequate blood supply
Placenta is less efficient
Higher risks for
Cesarean delivery
Postpartum hemorrhage
Low Apgar scores, brain damage, death
Labor induction at 41-42 weeks
Infant Mortality
INFANT MORTALITY
Number of deaths in the first year of life per 1,000 live births
Contributing factors
Physical defects
Low birth weight – preventable
Brain and Neuron Development
NEURON DEVELOPMENT
Neurons store and transmit information
Communication between neurons happens in synapses
Neurotransmitters are released and lock into next neuron
Stimulation important for synaptic connections to survive
Synaptic pruning
Glial cells
Myelination
BRAIN PLASTICITY
When areas are not yet committed to specific functions
High potential for learning
If one area is damaged, other parts can take over
Brain more plastic during the first few years than later in life
Overabundance of synaptic connections
Sensitive Periods and Brain Growth
SENSITIVE PERIODS
Romanian orphanages
Early and prolonged institutionalization
Decrease in size and activity in cerebral cortex
Prefrontal cortex especially impacted
Emotion regulation, stress management
Activation of areas responsible for positive emotion diminished
Overwhelming environments interfere with potential
Keep activities at their level
Cause children to withdraw stimulus deprivation
Experience-expectant brain growth (foundation)
Early brain development dependent on ordinary experiences
Opportunities to explore, interact, hear language and other sounds
Experience-dependent growth
Additional growth and refinement of structures due to experiences
Dynamic Systems Theory
DYNAMIC SYSTEMS THEORY OF DEVELOPMENT
Mastery of motor skills involves complex systems of action
Each skill is a product of
Central nervous system development
Movement capacities
Goals the child has in mind
Environmental supports
Learning Capacities
LEARNING CAPACITIES
CLASSICAL CONDITIONING
Neutral stimulus
Paired with stimulus that elicits a reflexive response
With repeated exposure, neutral stimulus produces behavior
Unconditioned stimulus
Naturally produces a reflexive response
Unconditioned response
Reflexive response to the unconditioned stimulus
Neutral stimulus
Does not naturally lead to the reflex
Becomes conditioned stimulus by producing conditioned response
OPERANT CONDITIONING
Infant acts on environment
Actions are followed by stimuli
Those subsequent stimuli
Impact probability of the behavior will occur again
Reinforcer
Stimulus that increases the occurrence of an action
Punishment
Stimulus that decreases the occurrence of an action
HABITUATION
Gradual reduction in the strength of a response
Due to repetitive stimulation
Once we are used to certain stimuli
A new stimulus will cause responsiveness to return
This is called recovery
Novelty preference
Recovery to new stimuli
Used in studying infant recent memory
Familiarity preference
More time between habituation and learning phase
Used in studying remote memory
Piaget’s Cognitive Development Theory
PIAGETS COGNITIVE DEV THEORY
Sensorimotor stage
First 2 years of life
Schemes
Organized ways of making sense of experience
Adaptation
Build schemes through interaction with environment
Two processes of adaptation
Assimilation
Accommodation
Sensorimotor stage
Infants learn through their sensory and motor activity
Move from reflexive and random responses to goal-oriented responses
Schemes become more elaborate
Move between 6 substages
Circular reaction
Build schemes by repeating chance event
That they performed
Substage 1 (birth-1mo): reflexes
Repeat those behaviors even when typical stimulus is not present
Substage 2 (1-4mos): primary circular reaction
Repeat pleasurable behaviors that first occur by chance
Substage 3 (4-8mos): secondary circular reactions
Move focus to environment
Repeat actions that bring interesting results
Substage 4 (8-12mos): coordination of schemes
More deliberate behavior
Coordinate learned schemes
Attain goals, anticipate events
Substage 5 (12-18mos): tertiary circular reactions
Curiosity and experimentation
Substage 6 (18mos-2yrs): mental combinations
Mentally represent events
Do not have to act on it to think about it
Object permanence
Understanding that objects exist when out of sight
Develops between 3rd and 6th substage gradually
Information Processing
INFORMATION PROCESSING
Hold information in three parts
Sensory register
Short-term memory
Long-term memory
Mental strategies
Operate and transform information as it flows through different parts