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The Bare Bones ofHuman Anatomy
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The function of the skeletal system is:– To provide the supporting framework – To protect the body organs
Bone is a living tissue complete with blood supply and nerves
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Bone
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Bone Shape
The shapes of the bones allow them to perform specific functions more effectively
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Short Bones:– Include bones of ankle (i.e. tarsals) and wrist
(i.e. carpals)
Carpals
Tarsals
– Serve as good shock absorbers
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Long bones:
– Include femur of the thigh, humerus of the upper arm, and others
– Any bone whose length greatly exceeds its diameter
– Provide levers for movement
Femur Humerus
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Flat bones:– Include bones of the skull, scapula, ribs,
sternum, and clavicle– Largely protect underlying organs
Ribs
SternumBones of the skull
ClavicleScapula
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Irregular Bones:– Include bones of your face and vertebrae– Bones that cannot be placed in other groups– Fulfil special functions
Facial bones
Vertebrae
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Sesamoid bones:– Include patella– Oval, like a pea and found in tendons
Femur tendon
Patella
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Bone is very strong for its relatively light weight
The major components of bone are:– Calcium carbonate– Calcium phosphate– Collagen– Water
Bone CompositionCortical Bone
Spongy Bone
Medullary (marrow) cavity
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Bone Composition Cont’d Calcium carbonate and calcium phosphate:
– Make up 60-70% of bone weight– Provide much of the bone’s stiffness and resistance to pressing or
squeezing forces Collagen (a protein):
– Gives bone its characteristic flexibility and contributes to its ability to resist pulling and stretching forces
– With aging, collagen is lost progressively and bone becomes more brittle.
Water– Bone consists of much smaller proportion of water than other body
parts
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Bone Classification
According to the degree of porosity, bone can be classified into two general categories:– Cortical bone (low porosity)– Spongy or cancellous bone (high porosity)
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Cancellous bone Compact BonePorosity High (Low mineral
content and high collagen)Low (High mineral content and low collagen)
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Cancellous bone Compact BonePorosity High (Low mineral
content and high collagen)Low (High mineral content and low collagen)
Structure Honey comb Compact
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Cancellous bone Compact BonePorosity High (Low mineral
content and high collagen)Low (High mineral content and low collagen)
Structure Honey comb Compact
Characteristic Provides more flexibility but is not as stress resistant
Stiffer and can resist greater stress but less flexible
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Cancellous bone Compact Bone
Porosity High (Low mineral content and high collagen)
Low (High mineral content and low collagen)
Structure Honey comb Compact
Characteristic Provides more flexibility but is not as stress resistant
Stiffer and can resist greater stress but less flexible
Function Shock absorption due to its better ability to change shape
Withstanding stress in body areas that are subject to higher impact loads
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Cancellous bone Compact BonePorosity High (Low mineral
content and high collagen)Low (High mineral content and low collagen)
Structure Honey comb Compact
Characteristic Provides more flexibility but is not as stress resistant
Stiffer and can resist greater stress but less flexible
Function Shock absorption due to its better ability to change shape are important
Withstanding stress in body areas that are subject to higher impact loads
Location e.g., vertebrae Long bones (e.g., bones of the arms and legs)
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Effect of Fitness on Bone
When bones are subjected to regular physical activity and habitual loads, they tend to become denser and more mineralized– e.g. Right forearm of the right-handed tennis player is
more dense than her left one from using it more frequently
Inactivity works in the opposite direction, leading to a decrease in weight and strength. – e.g. Loss of bone mass has been noted in bed-ridden
patients, inactive senior citizens, and astronauts