Chapter 6 The Skeletal System

Functions of Bone Supports and gives shape to the body Protects internal organs Helps make movements possible Stores calcium & phosphorus Hemopoiesis-formation of blood cells by red bone marrow

Types of Bones Long—example: humerus (upper arm) Short—example: carpals (wrist) Flat—example: frontal (skull) Irregular—example: vertebrae (spinal cord)

Structure of Long Bones Structural components Diaphysis - shaft Medullary cavity - contains yellow marrow Epiphyses - ends of the bone; spongy bone contains red bone marrow Articular cartilage—cushions and covers epiphyses Periosteum—strong membrane covering bone except at joint surfaces Endosteum—lines medullary cavity

Microscopic Structure of 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 Haversian system (or osteon)—composed of concentric lamella, lacunae containing osteocytes and canaliculi, all covered by periosteum (Cont’d…)

Microscopic Structure of Bone and Cartilage (…Cont’d) Cartilage Cell type called chondrocyte Matrix is gel-like and lacks blood vessels

Bone Formation and Growth Sequence of development early—cartilage models replaced by calcified bone matrix Osteoblasts form new bone, and osteoclasts resorb bone

Division of Skeleton Skeleton composed of the following divisions and their subdivisions: Axial skeleton Skull Spine Thorax Hyoid bone (Cont’d…)

Division of Skeleton Appendicular skeleton (…Cont’d) Appendicular skeleton Upper extremities, including shoulder girdle Lower extremities, including hip girdle Location and description of bones

Differences Between a Man’s and a Woman’s Skeleton Size—male skeleton generally larger Shape of pelvis—male pelvis deep and narrow, female pelvis broad and shallow Size of pelvic inlet—female pelvic inlet generally wider, normally large enough for baby’s head to pass through it Pubic angle—angle between pubic bones of female generally wider

Joint (Articulations) Kinds of joints Synarthrosis (no movement)—fibrous connective tissue grows between articulating bones; for example, sutures of skull Amphiarthrosis (slight movement)—cartilage connects articulating bones; for example, symphysis pubis (Cont’d…)

Joint (Articulations) (…Cont’d) Diarthrosis (free movement)—most joints belong to this class Structures of freely movable joints—joint capsule and ligaments holding 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 (Cont’d…)

Joint (Articulations) (…Cont’d) Types of freely movable (diarthrotic) joints ball-and-socket (hip & shoulder) hinge (finger, knee, elbow) pivot (vertebrae--axis) saddle (finger base--opposing the thumb to the fingers) gliding: limited movement at superior & inferior art. processes(vertebrae) condyloid: oval projection fits in an elliptical socket (wrist)

The End