Week 3 187

Diaphysis is the main part of the bone

Epiphysis are found at the end of each bone, they have added surface area for muscle and ligament attachment

Epiphyseal line allows the shaft to increase in length

Medullary cavity is the space inside the bone that contains the yellow bone marrow in adults Metaphysis a edges slightly below the growth plate/head Types of Bone: Cortical bone: Outer layer of long bones (80% of skeletal mass) arranged in parallel lines in the direction where force comes. (outside of bone) Trabecular bone: Porous is structure, found in proximal and distal end of long bones & vertebrae. Makes up 20% of total skeletal mass. Cartilage becomes trabecular bone but by the age of 4 it can become cortical bone. As we grow these can decrease with age. Trabecular bone deteriorates as we age, in females this results in a loss of connectivity in individual trabeculae however in males the struts become thinner instead. Cartilage -> trabecular -> Cortical bone (4 years +) The skeleton is made up of bone mineral composed of calcium phosphate. This is embedded in a protein called collagen, collagen is essentially the steel reinforcing bars for concrete but for the bones. Bone growth: On average an adult has 3kg of solid bone (2 thirds mineral/inorganic, 1 third protein/organic) -constantly being formed and broken down (Bone turnover) Osteocytes: Hard cement that form around the collagen fibres. Essentially the cement. They regulate the flow of nutrients and minerals as well.Osteoclasts: Bone resorption (cleaners): remove the old bone Osteoblasts: Bone forming cells (builders) deposit on the proximal side of the growth plate (epiphysis) or bone break Two processes of bone turn over: Modelling: laying down of new bone(ceases once the growth plates seal) Remodelling: removal of the old bone (accelerates during menopause due to the sudden stopping of estrogen in the blood stream) Development of skeletal system: -Defines an individuals structure -provides an attachment point of muscles etc -protection for internal organs -provides a means of movement -living tissue undergoing considerable change across the lifespan

Early development of the skeletal system: Early embryo skeleton is comprised of cartilage. Bone is deposited at ossification centres. These double from birth until after birth.
Primary ossification centres: at the midpoint of long bones (lays down bones in utero at approx. 2 months of age in the womb) where the bones ossify outwards from the primary OC. Ossifying outwards until birth and then ceases to grow after birth.
Secondary ossification centre: Occurs after birth for post natal length growth and are found in the growth plate.
Epiphyseal plate and its layers. The cartilage forms, aligns and ossifies. It requires a blood supply, interruption of blood supply can impede normal growth. Bone growth ceases at different times for different bones. Growth ceases once the epiphyseal plates fuse to the shaft. Lower body seals growth plates quicker than upper body. Once fused the bone length is fixed. Majority of these bones are fused by the age of 18 of age. Smaller rounder bones continue to ossify from the centre outwards at this point from the primary centre. (carpals)
(Cartilage is replaced by bone tissues. Both prenatally and sometimes upto mid 20s)
(girls start ossification around 2 years earlier)
Progress of bone growth can be monitored with X-rays and radiographs.
Open or closed epiphyses (growth plates) indicate skeletal maturity.
Individual differences still occur give or take 3 years.
Humerus is seen to close at 16 years of age in girls and 18 years of age in boys
Bone mass and changes:
-Bone loss occurs with ageing
-maximusing bone mineral accrual density during growth is essential
Superannuation theory: (Increased bone mineral accrual during adolescence which means healthier bones during adulthood) being physically active, proper calcium intake helps maintain bone mass.
Measuring bone mineral accrual:
DXA: Dual X-ray absorptiometry (2D)pQCT: Peripheral quantitative computed tomography is a 3 dimensional (only able to be used on limbs etc.
Potential link between low birth weight and bone health: low birth weight at 6 months relates to low bone mineral content later on in the month. This can be related to mothers’ diet during pregnancy and or the baby’s nutrition during the first 6 weeks.
Choice of sport in adolescence:
-During growth, weight bearing physical activity promotes bone mineral accrual. (elite gymnansts vs water polo) the gymnasts had greater BMD and bone strength. Elite swimmers seem to have the same BMD as general population.
BMD: link with timing of sport,
Weight being activity is beneficial to BM accrual during growth,
Sport during childhood = small gains
Sport during peripubertal = large gains
Sport during puberty = large gains
Goal during childhood is banking an optimal amount of bone,
Exercise is protective in adulthood by slowing the rate of bone loss.
Bone loss occurs as early as mid 20’s and lose approx 1% a year.Composition of bone across lifespan: Bones become more brittle and suspectable to bone fracture across the lifespan. (cased by hormone levels, diet and especially decreased exercise)
Childhood there is equal organic and in-organic components. Older adults can have up to 7x more in-organic components to organic components.
Decline in sex hormones contribute to the loss of bone density.
-in men testosterone production declines gradually at the same time bone loss is linear and slow
-in women a rapid phase of bone loss occurs during the 5-10 years after menopause (Due to the immediate and dramatic decrease in estrogen)
-similar bone mass and growth however, menopause has a large drop to osteopenia and then osteoporosis. Calcium supplementation can slow bone loss by less than half as well as exercise to maintain bone by increasing bone formation.
-Calcium can slow bone loss by less that half the rate
-Exercise helps maintain bone mass by increasing bone formation
-Oestrogen hormone maintains bone by lowering absorption.

• Women accumulate less skeletal mass during growing years. (boys often get 2 more years of growth) women are affected by bone loss much greater and have up to 2-3x more fractures)
  Skeletal changes with age:
  -Joints become stiffer and less flexible
  -fluid in joints may decrease and the cartilage may begin to rub together and erode.
  -minerals may deposit in some joints (calcification)
  -hip and knee joints begin to lose structure (degenerative changes)
  Finger joints lose cartilage and bones thicken slightly (these changes are more common in women and this may be hereditary.
  Some joints such as the ankle change very little with ageing due to the amount of load and impact on it.
  The trunk becomes slightly shorter as the disks gradually lose fluid and become thinner, vertebrae lose some of their mineral content making each bone thinner, the spinal column becomes more curved and compressed (lumbar then thoracic)
  Bone spurs caused by ageing and overall use of the spine (May occur on the vertebrae)
  Osteoporosis: A skeletal disorder characterised by compromised bone strength predisposing a person to increased risk of fracture.
  -Osteoporosis results from a loss of bone mass and low bone strength. Bones become more porous
  Risk factors:
  -Increasing age
  -Females (3x higher than males) 30%f10%m over age of 35
  -Family history
  -lack of calcium and vitamin D
  -smoking and excess alcohol consumption
  -low body weight
  -low levels of physical activity
  -reduced oestrogen levels
  -medical history (celiac disease, thyroxine excess)
  -medication (long history of corticosteroids)
  Prevalence:
  ½ give up exercise
  ¼ give up work
  1/3 have difficulty with chores
  About 924,000 have osteoporosis
  Over ¼ of people 75+ have osteoporosis
  More common in women then man (29%) over 75 age
  The proportion of women with osteoporosis increases with age
  Bone density 2.5x lower of avg 30-year-old = osteoporosis
  Bone density 1-2.5x lower of avg 30-year-old = osteopenia

People with osteoporosis often become hospitalized from minor trauma fractures due to increased risk.
Increased incidence of fracture especially the hip
-perceived poor health
-increased pain
-high psychological distress
-risk of micro-fractures of vertebrae
-rib cage collapsed forward
-stopped posture
-standing height reduced
Exercising with Osteoporosis: (unpacked in lecture)
Avoiding fall risks, improve stability and load in a moderate setting.
Arthritis: A group of musculoskeltal conditions in which there is wearing and inflammation of the joints.
-Caused chronic pain, swelling, stiffness, disability and sometimes deformity.
Osteoarthritis occurs from a loss of structural integrity of elements of the joint capsule and the bone/cartilage near the joint centres. ( a direct degenerative condition)
Rheumatoid arthritis: chronic and progressive inflammatory disorder of joint and joint capsule which results in degradation of cartilage at the end of the long bones.
Risk factors (age, obesity, injury, genetic factory, auto-immune related)
-Twice as likely for females to have osteoarthritis.
-1/7 or 15% of Australians have arthritis
9% have osteoarthritis
1.9% have rheumatoid