lecture two: lifespan perspective of the musculoskeletal system Flashcards
movement
occurs from the interaction between sensory/perceptual, cognitive, and motor/action systems
sensory/perceptual system (afferents)
provide sensory info about body and environment
cognitive system
attention, planning, problem solving, motivation, and emotional aspects of motor control
motor/action system (efferents)
neuromuscular and bio mechanical systems control execution of functional movement
motor units
- defined as one motor neuron and all the muscle fibers it innervates
- basic functional units of skeletal muscle
motor unit activity represents the ____________ of the CNS and their role in motor control is widely studied
final output
functional motor unit
higher centers of the nervous system and the effector organs of movement
primary motor cortex
controls speed and force of movement
supplemental motor area
involved in preplanning movements
premotor cortex
visually guided movements
cerebellum
coordinates movements based on accuracy, timing, and intensity
basal ganglia
controls posture and adaptation to varying tasks or environments
__________ system composes execution structures for movement
musculoskeletal
two main periods of gestation development (prenatal)
- embryonic period: 0 to day 60 (approx 2 months or 8 weeks)
- fetal period: day 60 and on
stages of early development
- fertilization: day 1
- implantation: day 6/7
- gastrulation: day 15/16
gastrulation
- phase early in embryonic development of most animals during which single-layered blastula is reorganized into a trilaminar (“three-layered”) structure known as the gastrula
- three germ layers: ectoderm, mesoderm, endoderm
embryogenesis
eight weeks after fertilization, embryogenesis is complete and all limb structures are present
muscular system development (prenatal part one)
- muscular system develops from the mesodermal
- during 2nd half of gestation, rapid increase in NUMBER and SIZE of muscle fibers
- type I muscle fibers: slow twitch tonic fibers -> 21 wks gestation
- type II muscle fibers: fast twitch phasic -> 30 wks gestation
- all skeletal muscles are developed by birth (all muscles are “mixed muscles” meaning they are a combination of slow and fast twitch)
muscular system development (prenatal part two)
- change in direction of muscle fibers
~ alters muscle fiber orientation
~ i.e. trapezius develops into multiple fiber directions - splitting in myotomes
~ separating into multiple layers
~ i.e. biceps brachii has 2 heads - degeneration
~ formation of aponeurosis (sheet of connective tissue)
~ i.e. linea alba in rectus abdominis
muscular system maturation (infant and childhood)
- number and size of muscle fibers continue to increase
- differentiation in muscle fiber types
- increased muscular strength as muscles grow and mature
at birth, muscle mass is only ____ % of total body mass
25%
muscular system maturation for males
- 2 months to 16 yrs: 14 fold increase in fiber number
- fiber size and strength increases until adolescence
- 5 to 17 yrs: muscle mass increases to 41-53% of total body mass
muscular system maturation for females
- 10 fold increase in fiber number after birth
- more rapid increase in fiber size compared to males
- 3 to 10 yrs: peak increase in size
- 5 to 17 yrs: muscle mass increases to 41-42% of total body mass
muscular system maturation (adolescence)
- relative type I and type II fiber ratio has reached adult level
- growth spurt: increase in skeletal and muscle length
- length-tension relationship is modified through muscle lengthening as bones grow
- muscles increase in length through addition of sarcomeres and fibers
- increased strength -> increased muscle mass
- males: rapid increase in strength and endurance throughout entirety of adolescence
- females: peak strength at onset of puberty
- peak strength seen in young adulthood (early 20s-30s)
muscular system maturation (adulthood)
- muscle strength declines at age 30
- coordination declines in 30s
- varies among individuals (more physically active adults may not experience as significant of a decline)
- increased occurrence of muscle strains
- 50 years old: steady decline in strength; impaired function
- between 50-70 years old: 30% decline in strength
- 70 years old: rapid decline in strength
each decade, ____% of muscle mass is lost
5%
muscular system aging (older adults)
- sarcopenia
- loss of muscle mass and function
- decrease in: number of fibers, mass of fibers, and number of functional motor units
- senile muscular atrophy
- muscle wasting
- decrease in strength and speed of muscular contraction
- decreased mobility
- greater decline in trunk and lower extremities compared to upper extremities
- pattern of muscle weakness is proximal -> most prominent in back, abdominals, and quadriceps -> impaired balance and equilibrium reactions
in older adults, there is an increased rate in loss of ____________ fibers compared to ____________ fibers
- type II fast twitch; type I slow twitch
- decreased speed of contraction results in loss of muscle power and decreased mobility within limits of postural stability
- slower reaction times and initiation of voluntary movement leads to impaired balance strategies
- i.e. impaired ability to perform sit to stand leads to increased occurrence of falls
skeletal system structures
- bone cells
- osteoblast: create bone
- osteoclast: absorb bone
- bone tissues
- compact bone: hard and dense outer layer
- spongy bone: flexible inner layer containing bone marrow
skeletal system functions
- provides structural support for body
- protects vital organs
- stores minerals such as calcium and phosphorus
- acts as lever for movement
- stores blood producing cells in bone marrow
diaphysis
shaft of long bone
epiphysis
end of long bone
epiphyseal plate
area where bone grows
epiphyseal lines
area where epiphyseal plates have fused together
- growth is not possible
skeletal system development (prenatal part one)
- all bones and cartilage develop from the mesenchyme
- 3rd to 8th wk: bone and cartilage are differentiated and bone develops
- 5th wk: mesenchymal cells condense and differentiate -> occurs first in extremities (UE before LE)
- 6th wk: chondrocytes form cartilage of long bones
skeletal system development (prenatal part two)
endochondral ossification
- growth of cartilage model: 6th wk
- development of primary ossification center: 7-11th wk
- development of secondary ossification center: after birth
- formation of articular cartilage and epiphyseal plate: after birth
skeletal system maturation (at birth)
- diaphysis are well ossified
- formed by primary ossification center
- epiphysis are still cartilaginous
- formed by secondary ossification center
- most bone fractures occur in this section of long bones
primary and secondary curves
- primary curves
- thoracic and sacral regions of spine
- kyphotic
- formed at birth
- secondary curves
- cervical and lumbar regions of spine
- lordotic
- formed through weight bearing during walking
skeletal maturity (I&C)
- achieved when epiphyseal plates close
- SMI -> skeletal maturity indicators
bone age (I&C)
- helps doctors estimate maturity of child’s skeletal system
- usually done by taking single x-ray of left wrist, hand, and fingers
- if scoliosis present, can also be done x-raying iliac crests (Risser Sign)
- safe and painless procedure that uses small amount of radiation
skeletal system maturation (I&C)
- bone grows rapidly
- influenced by genetics, health, and nutrition, and weight bearing
- changes in growth
- newborns -> head and trunk are disproportionately larger than adults
- throughout childhood, pelvis and lower extremities change in length, rotation, angle, and torsion
- bone remodeling -> weight bearing and movement drive skeletal changes
sutures (I&C)
hold together the bones that form the skull
fontanelles (I&C)
soft areas where the bone hasn’t fused yet
- posterior: closes at 2-3 months
- anterior: closes at 12-18 months
clinical implications of sutures and fontanelles
- craniosynostosis -> premature closure of sutures
- cranial orthoses -> worn to help the bones to grow evenly again; won’t be helpful at 18 months
skeletal system maturation (adolescence)
- bone remodeling and growth continues
- influenced by hormones, physical activity, and nutrition
- growth spurts influence skeletal changes
- girls: 12-14 yrs old
- boys: 14-15 yrs old
- trunk grows before legs
- skeletal growth occurs quicker than muscular growth (improper length-tension relationship leads to decreased muscle flexibility)
skeletal system maturation (growth plates)
- cranial bones have complete fusion at 18 months to allow for development of skull and brain
- all epiphyseal growth plates close at age 25, typically many are closed before this and your done growing prior to this age
- precautions
- fracture across growth plate can lead to asymmetrical growth of that joint
- use of ultrasound is contraindicated over epiphyseal areas in children
skeletal system maturation (adulthood)
- bone growth is complete
- bone remodeling and density can increase with
- weight bearing
- muscular contraction
- adequate nutrition and calcium intake
- changes in bone mass
- peak during late 20s to early 30s
- remains stable between 30-50
- bone resorption exceeds bone formation after age 50
skeletal system aging (older adults)
- loss of bone mass
- associated with estrogen decrease
- females: ~1% per yr before menopause; 4% during first 4-5 yrs after menopause then 1% per yr
- males: ~0.5% per yr
- osteopenia: bone loss to where bone mineral density is lower than normal but not low enough to be osteoporosis
- increased risk of fractures
- associated with estrogen decrease
- deficient mineralization of bone matrix
- associated with deficiencies in vitamin D, calcium, and phosphate
- impairments include diffuse pain, muscle weakness, and intolerance with mechanical load (i.e. weight bearing)
- osteomalacia: softening of bones
structural changes in cartilage of older adults
- water content decreases
- extracellular matrix becomes rigid
- death of chondrocytes
- hyaline cartilage is replaced with fibrocartilage
- decreased capacity for repair and healing
functional impairments in older adults
- decreased strength and flexibility
- poor posture
functional implications (prenatal)
- concerns
- malleable skeletal system in confined environment change fetus’ position and mechanical forces applied to fetus
- deformities due to intrauterine molding
- diagnoses
- club foot
- talipes equinovarus
- congenital deformity
- congenital hip dysplasia
- atypical development of hips
- congenital limb deficiency
- a portion of upper/lower limb does not form completely or forms abnormally
- club foot
functional implications (infancy and childhood)
- concerns
- vulnerability of growth plate and cartilage to trauma
- if an injury occurs here, disruption in blood and nutrients can cause permanent damage to growth of involved limb
- increased risk of ligament tears or growth plate fracture due to traumatic mechanisms of injury or excessive repetitive stress
- typically occurs with high velocity activities
- vulnerability of growth plate and cartilage to trauma
- diagnoses
- epiphyseal infection and injury
- growth plate fracture
- apophyseal avulsion (due to sudden forceful muscular contraction)
- nursemaid’s elbow (common in toddlers and preschoolers)
functional implications (adolescence)
- concerns
- increased occurrence of stress fractures and apophyseal avulsion fractures
- diagnoses
- stress fracture (incomplete fracture commonly occurring in weight bearing bones)
- apophyseal avulsion fracture (typically occur in pelvis, hip, and tibial tuberosity)
- slipped capital-femoral epiphysis (slippage of femoral head due to damage to growth plate)
- scoliosis (abnormal curvature of spine; common in females)
functional implications (adulthood and older adults)
- concerns
- decreased strength and endurance due to age-related changes in bones, muscles, and cartilages
- increased risk of fractures due to changes in bone mineral density
- diagnoses
- back pain secondary to disc changes
- osteoporosis (bones become weak and brittle; bone resorption > bone formation)
- osteoarthritis (typically occurs in weight-bearing joints; overweight or obese individuals; accumulated micro trauma and inflammation)
precision medicine
- a form of medicine that uses information about a person’s genes, proteins, environment, and lifestyle to prevent, diagnose, or treat disease
- this includes a person’s age!
