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The Skeletal System Anatomy and Physiology Bone • A connective tissue • Contains bone tissue, cartilage, fibrous connective tissue, blood, and nervous tissue • It is alive! Functions • Provides points of attachment for muscles • Protection • Support • House blood producing cells • Store inorganic salts and minerals A typical bone • Epiphysis: large knob on the ends • Diaphysis: long shaft • Periosteum: covering over all • Compact bone: hard and rigid outside • Spongy bone: spongy and contains marrow • Articular cartilage: smooth surface on bone ends Spongy bone and marrow • Spongy bone is near the ends in the epiphyses • Contains red marrow, which produces blood cells (fills an infant’s) • Yellow marrow is in the medullary cavity, and stores fat, more in an older adult Compact Bone osteocyte • Tightly packed • Cells are called osteocytes • Surrounded by fibers and cemented by hard background • The structure forms around an osteonic canal, with blood vessels and nerves in the center Osteonic canal Osteonic Canals: bone grows in concentric circles Only in the compact bone! Bone Cells • Osteoblasts: are bone forming cells • When they mature and become surrounded with the hard matrix, they are osteocytes • Osteoclasts: break down bone Osteoblasts and Osteoclasts • When would osteoblasts be working? • When forming new bone for growth, repair, replacement of aging or dying bone • When would osteoclasts be working? • When dissolving older bone containing dead cells, or to release calcium into the bloodstream if needed Calcium Levels • If too low, parathyroid gland senses this and secretes parathyroid hormone (PTH) • PTH stimulates osteoclasts to break down bone and release calcium into blood • Calcium levels in the blood return to normal Calcium Levels • If too high, thryoid gland senses this and secretes calcitonin • Calcitonin stimulates osteoblasts to form new bone, depositing calcium in the new bone • Calcium levels in blood return to normal Why do we need calcium in the blood? • • • • For muscle contraction Nerve impulse conduction Blood clotting Other processes Orange: is axial Yellow: is appendicular Types of Skeletal Joints • Fibrous: immovable, ex: sutures of skull • Cartilaginous: bones connected by cartilage; limited movement; ex: vertebrae • Synovial: bones surrounded by capsule and synovial membranes; ends of bones are covered in cartilage and surrounded by synovial fluid; lots of movement Fibrous • Connected by thin layer of fibrous connective tissue Cartilaginous • Connected by cartilage • Limited movement, as when back is twisted or bent Synovial Synovial • Ball and Socket • Hip and shoulder • Ball shaped head joints with the cup of the other bone • Circumduction Synovial • Condyloid: oval shape of one bone joints with elliptical cavity of the other Synovial • Gliding: surfaces are nearly flat • Wrist, ankle Synovial • Hinge: convex surface joins with a concave surface • Flexion and extension • Elbow and knee Synovial • Pivot: can rotate around a central axis • Proximal ends of radius and ulna Synovial • Saddle: surface of bones are both convex and concave; fits in • Only occurs in the joint between the carpal and the metacarpal of the thumb