Physical growth and change lecture

Physical Growth and Change:

• Patterns of growth and change in the size, shape, characteristics and process of the body

  • Cephalocaudal

  • Proximodistal

• Closely linked to the development of sensory, perception and motor abilities.

• Influences what people can do, think& fell

• Influences how people view themselves

• Influences how we view others

Prenatal Growth:

• Development before birth

• Consists of 3 stages

• Germinal stage - fertilisation to 2 weeks

• Embryonic stage - 2 weeks to 8 weeks

• Foetal stage - 8/9 weeks to birth

Germinal stage:

• First and shortest stage of prenatal development

• Fertilised egg -  zygote

• Zygote begins to divide and becomes known as a blastocyst

• Blastocyst travels along the fallopian tube to the uterus where it implants itself in the uterus wall

• Placenta and umbilical cord begin to develop.

Embryonic stage

• Second stage of prenatal development

• Important stage for cell differentiation & developing major organs & structures

• The embryo develops three layers of cells (ger, layers)

• Each layer forms different structures of the body

  • Ectoderm (outer)

  • Mesoderm (middle)

  • Endoderm(inner)

• At 8 weeks the embryo is approx. 1 inch long

• Brain begins to form

• Face begins to form

• Arms and legs begin to form &move

• Connections between the brain & body start to establish

• Heartbeat is detectable by ultrasound

Foetal stage:

• Third stage of prenatal development

• Period of rapid growth & development

• The foetus becomes more complex and active

• Structure & functioning of organs becomes refined

• 12 weeks: facial features & limbs & sex organs are distinguishable; arms, legs, head & mouth moves

• 16 weeks: fingernails & toenails are forming, able to roll over in the womb, mother can feel movement of the foetus

• 20 weeks: structures of skin have fully formed, heartbeat can be detected by stethoscope, sucks thumb

• 24 weeks: eyes are fully formed and open, grasping reflex is present

• 28 weeks: various sections of brain are recognisable, breathing movements begin to occur, very active

• 32 weeks: lungs mature, able to hear & respond to sounds and vibrations

Prenatal environment - Teratogen

• Teratogen - substances or conditions that can damage an embryo or foetus

  • Maternal diet

  • Maternal age

  • Maternal health - diseases/chronic illnesses (Chicken pox, not harmful for mother but fatal for babies)

  • Maternal alcohol / tobacco use

  • Maternal drug use

  • Maternal prenatal support

• Partner age

• Partner alcohol / tobacco / drug use

• Environmental hazards - e.g. workplace & exposure to certain chemicals

Teratogens and timing:

• As early as 3/4 weeks you already have CNS development so exposure to these teratogens can already have an impact.

Physical growth & change in infancy (Birth - 2 years)

• Rapid changes in height and weight

• On average infants at birth are between 45 - 55 cm long and weight between 6-10 pounds

• By 4/5 months infants weight doubles (from birth weight)

• By 12 months infant weights triple

• On average infants grow 2.5cm per month in their first year (1.5 x their birth weight)

• Rapid growth & plasticity of the brain and nervous system

• Cycle of synaptogenesis & pruning  (lots of brain connections that grow and some die (pruning))

• At birth - brain is approx. 25% of its adult weight (1/4 entire body size)

• In young children, the brain is disproportionately big compared to the proportionality of the adult brain.

• By 2 - brain is approx. 75% of its adult weight (1/5 body size)

Physical growth in early childhood

• Continuing increase in height and weight (but at a slower rate than in infancy)

• Brain & head continue to grow less quickly

  • Lateralisation

  • Handedness (favour left or right)

• Body shape & proportions change

  • Trunk of body, arms & legs lengthen

• Body becomes stronger

  • Muscle size increases

  • Bones strengthen

Physical growth in middle childhood

• Slow and steady increase in height and weight

• Two major growth spurts of the brain

  • 6-8 years - growth in sensory and motor areas of the brain

  • 10-12 - growth in the frontal lobe of the brain

• Body continues to become stronger & more muscular - body strengthen doubles; bones continue to harden

• Increase in agility and endurance

Physical growth in adolescence

• Physical maturation (transformation of the body into an adult like form)

  • Puberty

  • Primary characteristics (development of structure & organs related to reproduction)

  • Secondary characteristics (Signs of maturation that do not directly involve the reproductive organs)

Factors influencing Physical growth:

• Genetics / hereditary

• Hormones

• Pre-natal environment

• Post natal; environmental stimulation

• Postnatal environmental deprivation

• Nutrition

• Sex

• Ethnicity

• Socio-economic status

• Injuries & accidents

• Illness / infectious disease

Physical change in adulthood:

• Physical development is largely complete in early adulthood – peak of height, muscle tone & strength

• As adulthood continues, people begin to notice gradual physical changes as part of the ageing process

  • Some of these changes are directly related to age & biological/genetic process – Primary Ageing

  • Some of these changes are related to lifestyle choices, illness & other individual factors – Secondary Ageing

Biological Theories of Ageing:

Wear and Tear Theory

• Body wears out due to years of use and exposure to environmental stressors

Cellular Clock Theory – Hayflick Limit

• Universal genetic process that triggers age related physical change and limits lifespan

• Genetically programmed time limit, after which cells lose their ability replicate themselves accurately