The Skeletal System

The skeleton Supports the body, protects internal organs, provides movement, stores mineral reserves, is a site for blood cell formation 206 bones in the human Two parts Axial-supports the central axis and consists of the skull, vertebral column, and rib cage Appendicular-includes arms, legs, pelvis, and shoulders

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Structure of bones Bones are living cells and protein fibers surrounded by calcium deposits Bones are surrounded by connective tissue called periosteum that allows blood vessels to pass through to carry nutrients Compact bone is dense (but not solid) with Haversian canals that contain blood vessels and nerves

Structure of bone Spongy bone is inside compact bone located at the ends of long bones and the middle of flat bones Spongy bones adds strength without adding mass

Bone cells Osteocytes-mature bone cells; embedded in the bone matrix or tissue Osteoclasts and osteoblasts line the Haversian canals and surfaces of compact and spongy bone Osteoclasts break down bone Osteoblasts produce bone Bones are continuously remodeled

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Bone marrow Found within bones Two types Yellow marrow-made primarily of fat cells Red marrow-produces red blood cells, some white cells, and cell fragments or platelets