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Learn about the axial skeleton, including the skull, vertebral column, and bony thorax. Discover their functions, characteristics, and curvatures of the spine. Understand the different types of vertebrae and the ligaments and discs that support the spinal column. Explore the ribs and the pelvis, and learn about the gender differences in pelvis structure. Finally, understand the function and classification of joints, as well as the stages of bone repair.
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Skeletal System Axial Skeleton
Axial Skeleton • Includes 80 bones of the skull, vertebral column and bony thorax • Functions: • Supports head, neck & trunk • Protects brain, spinal cord and thoracic organs
Skull • Composed of flat bones • Function: • Used for attachment of head muscles & protects the brain
Sutures of the Skull • Sutures: interlocking joints that unite skull bones • Coronal: where parietal bones meet frontal • Sagittal: where 2parietal bones meet superiorly • Squamos: where parietal and temporal bones meet on lateral aspects of skull • Lambdoidal: where parietal bones meet occipital bones meet posteriorly
Vertebral Column aka the Spine • Location: runs from the base of the skull to the coccyx (tailbone) • Function: • Surrounds and protects the spinal cord • Provides attachment sites for ribs and back muscles
Vertebral Column • Characteristics • 26 interconnected irregular bones • Provides a flexible, curved structure • Serves as axial support of the trunk
Vertebral Column • Curvatures of the Spine: • S-shaped to prevent shock to head in motion • Allows for trunk flexibility • Increases resiliency & flexibility of the spine • Functions like a spring, not a rod • Cervical & Lumbar Curves: concave posteriorly • Thoracic & Sacral Curves: convex posteriorly
Lordosis: aka sway back An accentuated lumbar curve Kyphosis: aka hunchback An exaggerated thoracic curve Scoliosis: the twisted disease An abnormal lateral curvature in the thoracic region Typical in girls in late childhood Abnormal Curvatures of the Vertebral Column
Cervical Vertebrae • 7 total extending from base of skull to ~ shoulder line • Numbered C1-C7 • Smallest & lightest vertebrae • Unique vertebrae • Atlas or C1: no body; holds the occipital bone, allows nodding motion (“yes”) • Axis or C2: acts as a pivot for rotation; shake head (“no”)
Thoracic Vertebrae • 12 total; runs through mid-back • Numbered T1-T12 • Larger than cervical • Longer, palpable spinous processes • Ribs attach here posteriorly
Lumbar Vertebrae • 5 total • Numbered L1-L5 • Huge bodies and short spinous processes • Holds most of body weight & stress; very sturdy
Sacrum & Coccyx • Sacrum • Formed from 5 fused vertebrae • Numbered S1-S5 • Makes up posterior wall of pelvis • Strengthens & stabilizes pelvis • Coccyx • 4 fused vertebrae
Ligaments of the Spine • There are several; only 2 you need to know • Anterior Longitudinal Ligament: resists back hyperextension • Posterior Longitudinal Ligament: resists back flexion
Intervertebral Discs • Cushion-like pads between vertebrae • Asts as shock absorbers during motion • Makes up ~25% of length of column • Flattens during the day
Ribs • Flat bones • 12 total pairs • Attach posteriorly to thoracic spine • Function: • Protect thoracic organs • True Ribs: the superior 7 pairs • Attach directly to sternum by costal cartilage • False Ribs: the inferior 5 • 8-10: join each other by cartilage and indirectly attach to sternum • 11& 12: the floating ribs, no anaterior attachment
Pelvis • Has 2 regions: true and false pelvises • False pelvis superior to true pelvis • True pelvis dimensions are a concern to child-bearing women • Pelvic structure differs between men and women
Men Narrow outlet Heavier & thicker bone structure Ilia less flared, more vertical Sacrum long and curved Ischia close together Less rounded pubic arch Women Inlet circular & large Pelvis shallow, lighter & thinner Ilia flare laterally Sacrum shorter & less curved Ischia farther apart & shorter Pubic arch is more rounded Gender Difference of Pelvis
FUNTION OF JOINTS • They hold bones together. • Allow the rigid skeleton mobility Joints are classified in 2 ways: • Functionally –amount of movement • Structurally – type of tissue
Functionally- amount of movement • 1. Synarthrosis- immovable • Ex) sutures in skull • 2. Amphiarthrosis- slightly movable • Ex) intervertebral joints • 3. diarthrosis-freely movable • Ex) limbs
Structurally- tissue type between bones • 1) Fibrous- connected by fibrous tissue • - sutures skull • 2) Cartilaginous- connected by cartilage • -pubic symphysis • 3) Synovial- separated by a joint containing fluid • -6 types based on articulating bone surface
Types of Synovial Joints • 1. Plane Joint-wrist • 2. Hinge Joint- elbow • 3. Pivot Joint- ulna & radius • 4. Condyloid Joint- metacarpels • 5. Saddle Joint- thumb • 6. Ball & Socket- shoulder or hip