SKELETAL SYSTEM Mr. Mackay

SKELETAL SYSTEM Made up of all the bones, teeth and connective tissue of the body. –Ligaments, tendons, cartilage Adult has 206 bones, children 300. Skeleton provides: –Support: Holds up body –Protection: For organs, brain, spinal cord –Movement: Provides structure for muscles to move body.

SKELETAL REGIONS Axial Skeleton: Main torso: –Skull, ribs, sternum, Vertebrae Appendicular Skeleton: Extremeties –Limbs, pelvis, shoulders

ANATOMY OF BONE Outer Layer: Made of compact bone. Very dense and hard. Inner Layer: Spongy bone. Medullary Cavity: Bone marrow produces new blood cells. –Osteoblasts work to build new bone. Bones made of calcium (hard) and collagen (soft).

BONE SHAPE ShapeExampleLocation LongFemur, tibia, fibula, humerous, radius, Ulna, metacarpals, metatarsals, phalanges Appendicular ShortCarpals, tarsals Appendicular FlatScapula, clavicle ribs, sternum, occipital, mandible Appendicular Axial Sesamoid (Shaped like a pea and found in tendon) Patella Appendicular IrregularFacial bones, vertebrae Pelvis Appendicular Axial 5

BONE CLASSIFICATION Cortical Bone: –Not very porous, is less flexible and more stiff. –Largely found in long bones to resist greater stress. 6

SPONGY BONE Spongy Bone: –Relatively high porosity, with a lower proportion of calcium phosphate. –Honeycomb in structure, and more flexible. –Important for shock absorption, and flexibility. (ie. Vertebrae) 7

BONE COMPOSITION 8 ComponentProportion of Bone Weight Function Calcium Carbonate Calcium Phosphate 60-70%Stiffness Higher in cortical bone Collagen (Protein)15-20%Flexibility Resistance to pulling/stretching Higher in spongy bone Water 20-25%Found in all bones

BONE HEALTH Diet: Food with calcium & protein. Exercise: Helps to densify bones and make them stronger. When bones are subjected to regular physical activity and habitual loads, they tend to become denser and more mineralized Protection: Use protective equipment when participating in risky activities.

BONE METAMORPHOSIS Bones can and do change over time. Young bones: Soft and pliable (Cartilaginous) Adult bones: More calcium is absorbed and they hardened. Senior Bones: Soften due to poor calcium consumption & utilization. Bones become more dense / stronger with habitual use and exercise. (Mineralized) 10

EXERCISE ADAPTATION When loaded, bone is strained and breaks down where stressed. Osteoblasts, along with protein and calcium, work to strengthen the bone at the stress points. Calcification occurs and the bone is strengthened…densified. Cortical bone of the appendicular skeleton densifies more than spongy bone. 11

EXERCISE ADAPTATION Minimal Essential Strain (MES) is the threshold amount of stress applied to bone necessary to elicit growth of new bone. Force > MES is required to signal osteoblasts production. MES = ~1/10 of breaking force. Training effects have a positive relationship to bone density.