Chapter 5 Skeletal system PDF

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Chapter 5 Skeletal system FUNCTION  Supports and gives shape to the body  Protects internal organs  Helps make movements possible  Stores calcium Hemopoiesis, or blood cell formation TYPES OF BONES  Four major types, according to overall shape of the bone  Long—Example: humerus (upper arm)  Short—Example: carpals (wrist)  Flat—Example: frontal (skull)  Irregular—Example: vertebrae (spinal cord)  Some also recognize a sesamoid (round) bone category  Example: patella (kneecap) STRUCTURE OF LONG BONES  Structural components  Diaphysis or shaft—hollow tube of hard compact bone  Medullary cavity—hollow area inside diaphysis bone that contains yellow marrow  Epiphyses, or ends of the bone—spongy bone that contains red bone marrow  Articular cartilage—covers epiphyses and functions as a cushion  Periosteum—strong membrane covering bone everywhere except at joint surfaces  Endosteum—lining of medullary cavity MICROSCOPIC STRUCTURE OF THE BONE AND CARTILAGE  Bone types  Spongy • Texture results from needlelike threads of bone called trabeculae surrounded by a network of open spaces • Found in epiphyses of bones • Spaces contain red bone marrow  Compact • Structural unit is an osteon—calcified matrix arranged in multiple layers or rings called concentric lamella • Composed of osteocytes, lacunae, and canaliculi • Covered by periosteum  Cartilage  Cell type called chondrocyte  Matrix is gel-like and lacks blood vessels BONE FORMATION AND GROWTH  Early bone development (before birth) consists of cartilage and fibrous structures

 Cartilage models gradually replaced by calcified bone matrix—process called endochondral ossification  Osteoblasts form new bone, and osteoclasts resorb bone DIVISION OF THE SKELETON Skeleton composed of the following divisions and their subdivisions:  Axial skeleton  Skull  Spine (vertebral column)  Thorax  Appendicular skeleton  Upper extremities, including shoulder (pectoral) girdle  Lower extremities, including hip (pelvic) girdle  Location and description of bones JOINTS Every bone except the hyoid (which anchors the tongue) connects to at least one other bone  Kinds of joints  Synarthroses (no movement)—fibrous connective tissue grows between articulating bones; example: sutures of skull  Amphiarthroses (slight movement)—cartilage connects articulating bones; example: symphysis pubis  Diarthroses (free movement)—most joints belong to this class • Structures of freely movable joints—joint capsule and ligaments hold adjoining bones together but permit movement at joint • Articular cartilage—covers joint ends of bones and absorbs joints • Synovial membrane—lines joint capsule and secretes lubricating fluid • Joint cavity—space between joint ends of bones • Types of freely movable joints—ball-and-socket, hinge, pivot, saddle, gliding, and condyloid...