unit 3 lecture 1 body systems support skeletal system includes bones cartilage joints and ligaments 206 bones in axial and appendicular skeletons axial skeleton 80 bones skull vertebrae sternum ribs appendicular skeleton arms and legs shoulder girdle pelvis 126 bones 64 superior 62 inferior mainly connective tissue bone cartilage predominant types functions support bones hard framework soft tissues supports provides anchor protection vital organs surround skull brain ribs sternum heart vertebrae spinal cord pelvis reproductive organs movement bones joints system of levers internally operated by muscles movement single part or total body sharp arrangement of bones and joint design determine movement possible at each joint manufactures red blood cells majority manufactured in marrow cavities storage fat internal cavities of bones converted to energy when needed minerals major storehouse 99 of calcium 90 of phosphorus also K Na S Mg Cu stored as mineral salts released into blood in ionic form when needed classification of bones by shape into 4 categories long femur tibia humerus metacarpals etc enlargements at each end where weight bearing and movement are important short carpals and tarsals rounded shape internal structure shock absorbers sesamoid bones enclosed in tendons or other tissue ex patella others in hand and feet function improve mechanical efficiency of muscles flat ribs scapula skull protect vital organs large surfaces for muscle attachment internal structure good shock absorbers irregular vertebrae small facial bones inner ear function specific to bone protection vertebrae facial bones sound transmission bones of the inner ear chemical composition organic materials called osteoid cell osteoblasts bone forming cells osteoclasts large specialized cells in endosteum destroy or reabsorb bone secrete lysosomal enzymes and metabolic acids phagocytize bone matrix osteocytes bone cells cells of osseous tissue osteogenic cells in endosteum periosteum or central canals give rise to new osteoblasts arise from embryonic fibroblasts multiply continuously osteo blasts mineralize organic matter of matrix osteocytes are osteoblasts trapped in the matrix they formed cells in lacunae connected by gap junctions inside canaliculi osteoclasts develop in bone marrow by fusion of 3 50 stem cells reside in pits that they ate into the bone bone matrix organic materials provide tensile strength fibers mostly collage resist bending twisting stretching inorganic materials resist compression forces include mineral salts primarily Ca and P matrix is hard therefore bone is hard bone properties combination of organic and inorganic materials bones very strong without being brittle remove inorganic salts by soaking in vinegar leaves only organic materials bone can be tied to a knot remove organic materials by boiling leaves inorganic materials brittle bone will crumble bones stronger in compression than tension organic materials less able to withstand tension compression during support and weight bearing fracture from tension before compression general microscopic structure bone matrix sheets or layers lamellae lacunae open spaces scattered throughout lamellae osteocytes in lacunae thin processes pass through openings in solid lamellae called canaliculi processes joined by gap junctions nutrients pass by diffusion from one osteocyte to another types of bone two organizations of materials same materials organized differently cancellous or spongy more space and less material shock absorber found where shock absorption is important short flat irregular bones ends of long bones lamellae arranged in thin spicules or plates of bone hard material called trabeculae lacunae found within trabecular plates osteocytes in lacunae trabeculae arranged in patterns many open spaces contain bone marrow looks like net or lattice bone is living tissue highly vascularized patterns reflect stress applied to bone trabeculae can realign to new stress patterns requires permanent change and takes time cortical compact hard more material and less space functions in support resists bending twisting and compression forces located in long bone shats covers cancellous bone composition many haversian systems or osteons each system has a haversian or central canal haversian system runs parallel to length of bone haversian canal function as transportation system contains blood vessels that supply bone contains nerves and other CT lamellae in concentric rings around haversian canal cylinder of solid tissue surrounding canal osteocytes in lacunae within the lamellae volkmann s perforating canals connect haversian system with external vessels externaly to haversian system at right angle transportation system blood vessels in out of haversian canal arrangement is concentric rings of solid material canaliculi channels extend from lacunae interconnect processes of osteocyte structure of long bones diaphysis shift long narrow part of bone center medullary marrow cavity length of diaphysis surrounded by cortical bone thickest in middle 1 3 shaft strength and thinner toward ends lined with endosteum membrane composed of areolar CT both osteoblasts and osteoclasts thin layer of cancellous bone contains red marrow early in life produces RBCs adult red marrow replaced by yellow marrow fat cells epiphyses bulbous expansions at ends of long bones contain cancellous bone covered by thin layer of cortical bone shock absorption articular cartilage covers articulating surfaces reduces friction prevents wear and tear hyaline cartilage periosteum double layered membrane covers outer surface except articular cartilage 1 inner or osteogenic layer primarily osteoblasts 2 outer or fibrous layer dense irregular CT contains fibers of sharpey or perforating fibers collagenous fibers secure periosteum to bone secure ligaments and tendons internal side penetrate into bone external side fibers of sharpey become entwined with fibers of tendons etc mechanically very secure attachment to bones hollow cylinder construction advantages stronger than solid bone of same cross section and lighter weight important larege forces during movement and weight bearing structure of short flat irregular bones constructed like the epiphysis interior is cancellous bone called the diploe covered by thin layer of cortical bone excellent shock absorber in flat bones vertebrae cavities contain red bone marrow produces RBCs in children RBCs from marrow of long and flat bones and