Development and aging of the body Flashcards
6 body systems
integumentary, skeletal, muscular, nervous, circulatory, endocrine
Skeletal System - Prenatal
Early skeletal system starts from mesodermal layer and differentiates into chondrocytes
- Cartilaginous scaffolding
- Primary ossification centers
start at 8 weeks gestation - 2 types of ossification:
- Intramembranous ossification
- Skull, clavicle
- Endochondral ossification
- All other bones
Skeletal System - Childhood to Adolescence
Process of secondary ossification centers or growth plate, or epiphyseal plate creating length in bone occurs
- Height gained after birth is almost exclusively the result of linear growth of skeletal bones
Skeletal System -
Adulthood to Older Adulthood
Bone continues to remodel but not grow
- Osteoclasts chew up bone
- Osteoblasts build bone
- Rate of loss increases over time
- Due to less activity, hormone
changes, less muscle - Bank bone before age 30
- Bone builders:
- Exercise (weight bearing)
- Calcium
- Estrogen (post-menopausal women)
Muscular System - Prenatal
Grow via hyperplasia and hypertrophy
- Muscles grow in diameter and length proportionately to bone growth
- 15-30% of muscle fibers remain undifferentiated at birth
- Speculation early activity can influence muscle typing
Muscular System - Childhood to Adolescence
After year 1:
- muscle fiber type percentages
are same as adults, individually
different
- Sigmoid pattern of weight reflects
primarily hypertrophy of muscle.
- Differences between sexes begin in
adolescence:
- Men (17yrs): 54% of body mass is
muscle
- Women (13yrs): 45% of body mass is
muscle
Muscular System -
Adulthood to Older Adulthood
Ages 25 to 50
- 10% muscle mass loss
- 50 to 80 years,
- 30% muscle mass loss
- After 80 years old
- 50% muscle mass loss
- Atrophy accounts for most loss of muscle until 50, then loss of fiber numbers as well (sarcopenia)
- Influence in decreased bone density
- Strength exercise can counteract atrophy in up to 70 year olds.
Muscular System - Sarcopenia
Physically inactive people can lose 3-5% muscle loss after 30 years old.
- Peak decline begins around 75 years of age.
- Causes:
- Reduced nerve signals
- Reduced anabolic hormones
- Reduced calories/nutrient conversion
- High stress levels
- Prevention
- Strength training
- Supplementation: creatine, hormone
Nervous System - Prenata
Neurogenesis is the division and propagation of neurons
- Month 3-4: all neurons a human will have in their brain is formed (overproduction & pruning)
- Proliferate at 250,000 neurons/min
- Pruning occurs to incorrect connections, or non-active neurons
- Neurons migrate to locations related to their function/specialization – done by month 6
- Migration and branching are particularly susceptible to teratogens
- Rapid growth means development is vulnerable to extrinsic factors.
Nervous System - Childhood to Adolescence
Brain size:
- 25% of adult weight at birth
- 80% by age 4
- 100% around age 25
- Size of neurons, branching dendrites, glial cells and myelination increase brain size
- Myelination of extrapyramidal (first few days after birth) and pyramidal motor neuron tracts increase signal speed to body
- Responsible for connecting brain to body for motor skills
Nervous System -
Adulthood to Older Adulthood
Decline typically from accumulation of extrinsic factors:
- Breaks in the neural network
- Demyelination of nerves
- Plasticity is the capacity of the brain to
change connections to adapt to new
demands.
- Exercise (cardiovascular) increases
neurogenesis, and new dendritic/synaptic connections through increased Brain Derived Neurotrophic Factor (BDNF)
Endocrine System - Childhood - Older Adult
Anabolic pathways
- Important in protein synthesis and growth
- Growth Hormone (GH)
- Childhood and adolescence
- Anterior Pituitary Gland
- Needed for linear growth
- Thyroid Hormones
- Whole-body growth (metabolism/bones)
- Gonadal Hormones
- Sex hormones
- Lead to fusion of growth plates at sacrifice of
linear growth (early maturers shorter) Older adults decrease in their hormone levels
