1. The Skeletal System

2. 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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Human Skeleton
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4. 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

5. 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

6. 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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Cross Section of a Bone Cell
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Bone Components
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9. 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