Skeletal System
Functions of the Skeletal System
Internal framework supporting the body.
Protects internal organs; fights disease by producing white blood cells.
Facilitates movement with muscle contraction/relaxation.
Stores calcium.
Forms blood cells (hematopoiesis).
Types of Bones
Long: Example - Humerus.
Short: Example - Carpals.
Flat: Example - Frontal.
Irregular: Example - Vertebrae.
Sesamoid: Example - Patella.
Structure of Long Bones
Diaphysis: Shaft; hollow tube of compact bone.
Medullary Cavity: Contains yellow marrow.
Epiphyses: Ends of bone; spongy bone with red marrow.
Articular Cartilage: Covers epiphyses, providing cushion.
Periosteum: Covers bone except joint surfaces.
Endosteum: Lines medullary cavity.
Structure of Flat Bones
Thin compact bone layer surrounding cancellous bone.
Cancellous bone contains open spaces (trabeculae).
Microscopic Structure of Bones
Connective Tissues: Bone and cartilage.
Spongy Bone: Trabeculae surrounded by open spaces; contains red bone marrow.
Compact Bone: Osteon structural unit; arranged in concentric lamellae.
Bone Development
Osteoblasts: Form new bone; Osteoclasts: Resorb old bone.
Bones develop through endochondral ossification.
Growth continues until epiphyseal plate becomes epiphyseal line.
Divisions of Skeleton
Axial Skeleton: 80 bones (skull, spine, thorax).
Appendicular Skeleton: 126 bones (upper/lower extremities).
Differences Between Male and Female Skeletons
Male skeleton larger; deeper and narrower pelvis.
Female pelvis wider for childbirth; wider pubic angle.
Age Differences and Environmental Factors
Skeleton matures around age 25; density decreases after age 50.
Nutrition and mechanical stress affect bone structure.
Joints (Articulations)
Connects bones; classified by movement:
Synarthrosis: No movement.
Amphiarthrosis: Slight movement.
Diarthrosis: Free movement (most joints).
Types of Diarthrotic Joints
Ball-and-socket: Shoulder, hip.
Hinge: Elbow.
Pivot: Radius-ulna.
Saddle, Gliding, Condyloid: Various joints allowing specific movements.