WEEK 8 INFANCY & CHILDHOOD

Growth

• Definition: An increase in the size of the whole body or specific parts, reflecting quantitative changes.

  • Growth is a complex process influenced by genetics, nutrition, and environmental factors.

• Duration: Predominantly observed during the first two decades of life, but continues at a slower pace throughout life.

• Mechanisms of Growth:

  • Increase in cell number (hyperplasia):

  • Predominates in early development.

  • Involves cell division and multiplication.

  • Increase in cell size (hypertrophy):

  • Becomes more significant as growth progresses.

  • Cells enlarge due to synthesis of more proteins and organelles.

  • Increase in intercellular substances (accretion):

  • Deposition of minerals like calcium in bones or collagen in connective tissues.

  • Essential for structural integrity and support.

• Focus: Primarily concerned with the size attained at a given time, indicating the extent of physical development.

Maturation

• Definition: The qualitative advancement of an individual towards a biologically mature state, characterized by functional competence.

  • Maturation involves differentiation and specialization of cells and tissues.

• Occurrence: A continuous process affecting all organs, systems, and tissues. It ensures functional readiness.

• Example: Skeletal maturity refers to a fully ossified adult skeleton, indicating the completion of bone development.

• Variability: The timing and tempo of maturation vary significantly between individuals, influenced by genetic and environmental factors.

  • Assessed through indicators like dental development, sexual maturation, and skeletal age.

Development

• Contexts:

  • Biological: Development of stem cells into specialized, functional cells, and complex systems.

  • Encompasses processes such as cell differentiation, morphogenesis, and organogenesis.

  • Behavioral:

  • Development of motor skills:

    • Acquisition of coordinated movement patterns.

    • Involves maturation of the nervous system and muscular strength.

  • Acquisition of socially acceptable behaviors:

    • Learning and internalizing societal norms and values.

    • Crucial for adaptive social interactions.

  • Intellectual and emotional development:

    • Cognitive abilities such as reasoning, problem-solving, and memory.

    • Emotional regulation, empathy, and self-awareness.

Importance of Learning Growth and Development (G&D)

• Understanding G&D is crucial throughout a degree in:

  • Exercise Delivery

  • Exercise Prescription

  • Motor Control and Motor Learning

  • Advanced Coaching and Programming

  • Applied Exercise and Sports Physiology

• Significance: Provides insight into how different individuals cope with physical activity at various life stages and how performance is influenced.

  • Helps tailor interventions and training programs to optimize outcomes.

Definitions of Human Lifespan

• Chronological Age: Actual age in years, representing the time elapsed since birth.

• Biological Age: Age of biological maturation, reflecting the progress of physiological development.

• Prenatal Development:

  • Germinal Period: Fertilization to the end of germ layer formation (weeks 1-2).

  • Characterized by rapid cell division and implantation in the uterus.

  • Embryonic Period: Days 14-56 (weeks 3-8) after fertilization; embryo stage.

  • A critical phase of organogenesis and structural development.

  • Foetal Period: 56 days to birth (last 30 weeks); developing human known as a foetus.

  • Period of rapid growth and maturation of organ systems.

Age Groups

• Postnatal Age: Period after birth, marked by significant growth and developmental milestones.

• Infancy: First year of life (0-1 year).

  • Perinatal: First week after birth, a transitional period for physiological adaptation.

  • Neonatal: First month after birth, characterized by dependency and rapid development.

• Childhood: 1 year to adolescence.

  • Early Childhood: Preschool years (1-4 years).

  • Middle Childhood: Elementary school years (5 years to adolescence).

• Adolescence: Generally between 10-18 years, variable onset and termination.

  • Males: 10-22 years.

  • Females: 8-19 years.

• Adulthood: Age 20 to death.

  • Young Adult: 20-40 years.

  • Middle Age: 40-65 years.

  • Older Adult: 65 years to death.

Infancy and Childhood Growth Patterns

• Infancy: Period of rapid growth across most systems, highly influenced by nutrition and care.

• Childhood:

  • Early Childhood: Continued rapid growth but at a decelerating rate.

  • Middle Childhood: Steady growth progress, with increased physical activity and cognitive development.

Development of Germ Layers

• Formation of the germ layers and embryonic folding during early development.

  • Ectoderm, mesoderm, and endoderm give rise to all tissues and organs.

Foetal Circulation

• Function: The maternal system provides O2 and nutrients to the foetus, removing CO2 and waste via the placenta.

  • Essential for foetal survival and development.

• Vascular Structures:

  • Umbilical Vein: Carries oxygenated blood from the placenta to the fetus.

  • Umbilical Arteries: Transport deoxygenated blood from the fetus to the placenta for re-oxygenation.

• Heart Shunts:

  • Foramen Ovale: Allows blood to bypass the right ventricle, going directly from the right atrium to the left atrium.

  • Ductus Arteriosus: Connects the pulmonary artery to the aorta to divert blood away from the lungs.

  • Ductus Venosus: Temp vessel from umbilical vein to inferior vena cava bypassing the liver.

Changes in Circulation After Birth

• Post-birth Changes:

  1. Lung inflation leads to increased blood flow to the lungs.

  2. Closure of the foramen ovale.

  3. Constriction of ductus arteriosus, leading to its closure.

  4. The umbilical vessels degrade after cutting the umbilical cord.

• Heart Size Growth: After birth, the left ventricle increases in size more rapidly, influenced by higher resistance in systemic circulation.

Changes in Heart Functions

• Heart Rate (HR):

  • Foetal HR starts at week 4 and can reach up to 200 bpm during contractions.

  • Newborn HR averages around 140 ± 20 bpm, decreasing with age.

• Stroke Volume (SV):

  • SV increases from birth (3-4 ml) to adolescence (60 ml).

• Cardiac Output (CO):

  • CO in children is lower than adults due to less stroke volume despite higher heart rates.

Respiratory Development

• Prenatal Conditions: Lungs filled with fluid, no gas exchange occurs.

• First Breath: Fluid expelled, triggers breathing.

• Growth: Lung weight increases 20-fold from birth to maturity, with alveoli development continuing postnatally.

Thermoregulation in Infants and Children

• Body Composition:

  • Higher BSA-to-mass ratio leads to faster heat dissipation.

  • Developing thermoregulation mechanisms such as sweating and blood flow.

Digestive System Development

• Enzyme Development: Lactase high at birth, decreases with age.

• Limited Teeth: 20 deciduous teeth by 30 months, affecting food breakdown.

Endocrine System

• Growth Hormone: Promotes growth through IGF1 and IGF2.

• Thyroid Hormones: Influences growth, maturation, and overall biological processes.

• Adrenal Hormones: Cru