NO BONES ABOUT IT! The Skeletal System Did you know? The adult skeleton has 206 bones

The Skeletal System Parts of the skeletal system Bones (skeleton) Joints (flexibility) Cartilages (cushion) Ligaments (connect bone to bone)

Functions of the Skeletal System Support the body (internal framework) Protect soft organs (vertebrae) Allow movement due to attached skeletal muscles Store minerals and fats (fats, clacium, phosphorus) Hematopoiesis (Blood cell formation)

The Skeletal System Two subdivisions of the skeleton 1. Axial skeleton (skull, ribs, spine) 2. Appendicular skeleton (pectoral girdle, pelvic girdle, bones of limbs)

Classification of Bones by Shape Long bones Have a shaft with heads at both ends Typically longer than they are wide Contain mostly compact bone Examples: Femur (longest bone in the body) Head Shaft Head Figure 5.1a

Anatomy of a Long Bone Diaphysis Epiphysis Compact bone Protected by periosteum (membrane) Epiphysis Ends of the bone Thin layer of compact bone But mainly spongy bone in the middle Protected by articular cartilage

Anatomy of a Long Bone Medullary cavity Cavity inside of the diaphysis Contains yellow marrow (mostly adipose) in adults Contains red marrow (for blood cell formation) in infants

Contain mostly spongy bone 2. Short bones Generally cube-shape Contain mostly spongy bone Example: Carpals Tarsals Patella Figure 5.1b

3. Flat bones Thin, flattened, and usually curved Two thin layers of compact bone inside Layer of spongy bone inside Example: Skull Ribs Sternum

4. Irregular bones Irregular shape Do not fit into other bone classification categories Example: Vertebrae Hip bones

Review: Bone is a type of connective tissue 2 Parts: 1. Cells (living) 2. Matrix (nonliving substance released by cells) A. Fiber B. Ground Substance

1. Cells 2. Matrix Osteocytes— mature bone cells Osteoblasts— bone-forming cells (germ cells or “bud” cells) Osteoclasts —bone-destroying cells (“breakers”) A. primarily collagen fibers flexibility tensile strength (the strength to endure stretching forces) B. calcium salts (hardness) contain calcium and phosphorus great compressional strength (the strength to endure squeezing forces) 2. Matrix

Classification of Bone by Tissue Type Two basic types of Tissue 1. Compact bone Homogeneous Looks “smooth” 2. Spongy bone Small needle-like pieces of bone Many open spaces (like sponge) Keep bones light Figure 5.2b

Microscopic Anatomy of Bone Figure 5.3a http://www.youtube.com/watch?v=4qTiw8lyYbs&NR=1

Microscopic Anatomy of Bone Osteon (Haversian system) A unit of bone containing central canal and matrix rings Central (Haversian) canal Opening in the center of an osteon Carries blood vessels and nerves Perforating (Volkman’s) canal Canal perpendicular to the central canal

Microscopic Anatomy of Bone Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings Lamellae Rings around the central canal Sites of lacunae

Microscopic Anatomy of Bone Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system connecting all bone cells to a nutrient supply

Microscopic Anatomy of Bone Figure 5.3b–c