Growth and Health Features of Human Growth
Chapter 4: Growth and Health Features of Human Growth
Overview of Growth Patterns
Rapid Growth in the First Year
Growth is very rapid during the first year of life.
Gradual Growth After Toddler Stage
Around the time children begin to walk and enter the toddler phase, growth slows and becomes more gradual.
Acceleration at Puberty
Growth accelerates again at puberty.
Mid-Adolescence to Early Adulthood
Growth remains gradual again from mid-adolescence (around age 15) to early adulthood.
Cephalocaudal Growth Pattern
Definition: Headfirst development where growth and development occur from the head downwards.
In early childhood, the head is larger in proportion to the rest of the body, making bodies appear disproportionate.
Proximodistal Growth Pattern
Definition: Development progresses from the center of the body outward.
Children gain more control over internal bodily functions as they grow.
Muscle Development
Muscle Fibers at Birth: All muscle fibers are present at birth.
As children grow, muscles become longer and thicker due to movement and use.
Fat Development
In Utero Fat Development: Fetuses accumulate more fat to help regulate body temperature.
First Year of Life: Fat development continues after birth.
Thinning After Walking: Fat may decrease due to increased muscle use once walking begins.
Adolescence Redistributes Fat
Fat distribution changes, particularly noticeable in girls.
Bone Development
Prenatal Bone Formation
Bones start as cartilage during prenatal development and gradually turn into hardened bone starting from the embryonic stage.
Cartilage bone develops from the inside out; the hardening begins internally.
Epiphyses
The ends of cartilage bones that are still made of cartilage; growth stops when they finish maturing.
Change in Number of Bones
Babies have fewer wrist bones (3 at birth become 9) than adults.
The skull contains more bones than an adult skull; infants' skull bones are composed of sections to facilitate delivery and development.
Fontanels
The growth spaces between skull bones that eventually fill in to complete skull formation.
Stamina Development
Childhood Increase in Stamina
Stamina increases throughout childhood; younger children play in short bursts and need more rest.
Heart and Lung Growth
Growth in heart and lung size contributes to increased stamina as children age, becoming consistent in both boys and girls.
In adolescence, boys generally experience more growth in kidney and lung capacity.
Secular Growth Trends
Modern Trends
Children today are generally taller and heavier compared to previous generations, influenced by improved health and nutrition.
Notable variations exist by country.
Growth Measurement Curves
Distance Curve: Measures the average size of a sample of children at each age (e.g., height and weight examples).
Velocity Curve: Shows the average amount of growth at each year interval (e.g., average height gain between ages 3 and 4).
Mechanisms of Physical Growth
Heredity's Role
Genetics significantly impact growth patterns, controlling hormone production and sensitivity.
Sleep (Key Mechanism)
Growth During Sleep: Growth hormones released by the pituitary gland during sleep promote growth.
Sleep duration decreases with age; children at age 3 generally sleep about 11 hours, decreasing to 9 hours by age 12.
The liver produces somatomedin during sleep, which contributes to muscle and bone growth.
Cognitive Impacts
Sleep problems are linked to cognitive issues, depression, and behavioral problems; insufficient sleep is especially concerning for adolescents due to emotional regulation.
Nutrition
Nutritional Needs of Infants
Infants require twice the nutritional energy of adults relative to their size.
Breastfeeding
Current Statistics
Approximately 91% of Canadian women breastfeed at some point, with 69% breastfeeding for at least six months.
Advantages of Breastfeeding
Exclusive breastfeeding is recommended for a minimum of six months and should continue for up to two years.
Breast milk offers essential nutrients and fewer chances of contamination, leading to fewer illnesses (antibodies present).
Adjustment to Solid Foods
Breast-fed infants typically adapt to solid foods more easily than formula-fed infants due to nutrient composition.
Picky Eaters
Eating Behavior in Infancy
Before walking, infants tend to eat passively while sitting; after beginning to walk, exploration takes precedence over eating.
Preferences
Children prefer familiar foods that they know; new foods may elicit uncertainty and reluctance to try.
Children need less food than adults and can thrive on accessible nutritious options.
Grazers vs. Meal Eaters
Some children may prefer grazing, leading to smaller amounts of food consumed over time rather than traditional meal settings.
Parental Influence
Access to healthy food options and restrictions on unhealthy foods can encourage healthier eating habits.
Puberty and Food Intake
Increased Nutritional Needs
Rapid growth during puberty increases food intake, although adolescents often exhibit poor dietary habits.
Essential nutrients, particularly iron for menstruating girls and calcium for bone density, become increasingly important.
Adolescent Growth Spurts
Timeline
Puberty lasts about four years, with girls beginning growth spurts around ages 11-12 and finishing by 15.
Boys begin at about 13, continuing until approximately ages 16-17.
Physical Changes
Involves elongation of bones and increased bone density, redistribution of fat, and development of primary and secondary sex characteristics (breast and hip development for girls; shoulder development and voice changes for boys).
Mechanisms of Maturation
Hormonal Contributions
The pituitary gland releases growth hormones that activate other glands:
Adrenal gland release of androgens.
Ovaries producing estrogen.
Testes releasing testosterone.
Nutrition and Exercise Effects
Improved nutrition can hasten the onset of menstruation, with body weight influencing leptin levels, which can affect reproductive cycles.
Psychological Effects of Puberty
Emotional Changes
The anticipation of changing bodies influences emotions surrounding puberty.
Pre-existing stressors can enhance mood variability, drawing attention to self-image and peer comparison, especially in girls.
Increased independence leads to more conflicts with parents.
The support of family and friends helps mitigate mood changes.
Timing of Puberty
Variability Among Adolescents
Early maturation in boys can foster confidence; late maturation may lead to anxiety.
Early maturation in girls can damage body image, while late maturation may bolster confidence and sociability.
Cultural Expectations
Early developers attract sexual attention and face heightened risks for early sexual activity and substance use.
Challenges to Healthy Growth
Malnutrition Issues
Statistics indicate 27% of Manitoba children live in poverty, further contributing to food insecurity (25% of Canadian children).
Malnutrition correlates with cognitive delays and impacts on attention, participation, and overall educational performance.
Eating Disorders
Anorexia Nervosa: Characterized by an intense fear of weight gain and distorted body image; leads to severe physical health consequences and mental health issues (10% mortality rate).
Bulimia Nervosa: Involved binging and purging behaviors potentially leading to severe health complications.
Intervention combines psychotherapy with nutritional education and family involvement.
Body Image Issues
Body Dysmorphia
Distorted self-image concerning body shape and size; affects both genders differently based on societal standards of attractiveness.
Obesity Concerns
Statistics
30% of children and young people are classified as overweight, with implications for long-term health and psychological impacts.
Risk Factors
Genetic predispositions and environmental factors influence obesity prevalence, such as dietary habits instilled from family environments.
Preventative Approaches
Child's Self-Responsibility: Encouraging children to understand their food needs instead of imposing strict dietary regimens can foster healthy habits.
Positive Reinforcement: Promoting nutritious food through enjoyable experiences (cooking together) can support healthier dietary choices without stigma.
Infant Mortality and Safety Concerns
Accidental Deaths
Major causes: motor vehicle accidents, drowning, and suffocation largely attributable to unsafe environments and underestimating children's capabilities.
Developmental Neurology
Prenatal Nervous System Development
Begins during the zygote stage; follows through with significant milestones such as the formation of the neural tube by the fourth week.
Neurons proliferate and migrate, establishing essential pathways for development.
Synaptogenesis
Increase in synapses leading to advanced cognitive ability; pruning enhances brain efficiency.
Myelination
The process of coating axons with a fatty substance to speed neural transmission, critical for cognitive development.
Experience-Expectant and Dependent Growth
Definitions
Experience-Expectant Growth: Brain development dependent on typical experiences.
Experience-Dependent Growth: Growth reliant on specific individual experiences, highlighting the importance of varied stimulation for brain development.
Chapter 5: Basic Sensory and Perceptual Processes
Overview
How individuals select, perceive, and organize environmental stimulation is closely tied to motor skills.
Sensory Development
Taste and Smell
Infants' sense of taste is well-developed at birth, showing preferences for sweet tastes.
Infants can identify their mother's scent soon after birth, influenced by maternal diet.
Touch significantly drives physical and emotional growth; reflexes depend extensively on tactile stimuli.
Pain Sensitivity
Infants exhibit heightened sensitivity to pain, facilitating soothing strategies through touch and sweet solutions.
Investigative Behavior in Infants
Touch Exploration
Infants utilize touch to explore, showing a strong preference for gentle tactile experiences.
They instinctively grab objects, investigate, and often place items in their mouths as part of their learning process.
Chapter 5: Perceptual and Motor Development
Perceptual Development
Development of The Senses
Hearing
- Newborns can hear a variety of sounds, but their hearing sensitivity increases over the first few months
- In utero everything is muffled and there are other sounds like heartbeat, they can hear outside noises but they’re less dominant
After birth, the brain will improve and be able to recognize sounds better with clearer pitches
At a few months old babies will begin to locate the direction of sounds, especially moms voice
- They will turn and look in the direction of sounds
They begin to be able to distinguish vowels from consonants, and prefer sounds in their native language
Around four months babies begin to like human voices, they don’t like higher or lower pitches
They begin to recognize their names at 4.5 months
At 6-7 months they recognize musical tunes
They prefer melodies that are harmonious rather than discordant
Vision
Least developed at birth, there’s a lot of shifts as development occurs
Visual Acuity: the smallest pattern that can be detected dependably
By 1 year, their visual acuity matches that of an adult, and preferences for complex patterns develop
Contrast Sensitivity: ability to process stimuli that vary in size and contrast
Babies at 2 months prefer large patterns with a lot of contrast
Poor acuity is due to weak muscles that control the lenses
Cones begin first levels of color processing; they’re not as developed or connected to the ganglion cells as they will be
Newborns see fewer colors because there are fewer neural connections between the cone cells and the brain, they connect at around 3 months
They’re more capable of seeing warmer, red tones
Integrating Sensory Information
- Infants integrate information from different sense
They pay more attention to sensory information that affects more than one sense
Intersensory Redundancy Theory: infants perceptual system is particularly sensitive to information that is presented to multiple sensory modes
They may interpret these sensations as more important and so pay more attention to them
Babies may begin to link body movements to music and will begin to mirror those movements
Complex Perceptual and Attentional Processes
- Babies use several cues to understand that goes together, this begins to happen at about 4 months
- Motion is one of these cues
- If different things are moving together, they belong together
Similarity in texture, color, and alignment of edges are other cues that are used
Perceptual Constancies
- Size constancy: the size of something stays the same even if it changes size in the retinal image
- This develops by 4-5 months
- Color, brightness and shape constancy is also achieved
- This allows the baby to make sense of their world and not be perpetually confused
Depth Perception
- Visual Cliff: before they’re crawling, if you put a baby over a fake cliff (visual cliff), their heart rate will lower, and they recognize something is different. Once the baby begins crawling/walking, they won’t want to go over the cliff. Their heart rate will increase; this is fear.
- This is due to the experience they gain from exploring
- Visual Expansion: as something gets closer it will get bigger
Motor Parallax: when something is in motion, and it's close to us, it looks like it moves faster than when its far away
Retinal Disparity: by four months, the brain is developed enough that this will occur, you receive two different inputs from both eyes, and your brain merges then when objects are closer its harder for this to be done
Monocular Cues: as babies interact with their environment they will begin to understand that certain things may be obstructed by other objects, so they have to move the obstruction to get to the desired item
The development of motor skills increases understanding of depth
Perceiving Faces
Newborns prefer faces with “normal” features, and features where they should be
They begin to distinguish faces by 2-3 months
Including human vs non-human
They spend more time looking at faces and features
By 3 months of age, babies will start to look towards the middle of the face, especially sections that move
Eyes, eyebrows, mouth
By 5-6 months they focus on spatial relationships of facial features to recognize faces
The distance between eyes, bottom of nose to top of the lip
In you show them a picture of a face they know but altered, they will dishabituate
In cases where babies have things which impair their vision, but it gets fixed, they will still recognize faces but not notice the differences
Experience with faces is needed for faces to develop fully
Preference for contrast and movement of faces
Attention
- Orienting Network: focus on unfamiliar stimuli, things that will be important
- Habituation, they understand things are safe and don’t need to be focused on, babies who habituate faster are more intelligent
- Executive Network: monitors thoughts, feelings, and responses
- Responsible for focused/selective attention
- Impact of pretend play
- Reminders to pay attention