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

Curvatures of the Spine

Abnormal Curvatures of the Vertebral Column 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

Lordosis & Kyphosis

Scoliosis

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 Coccyx 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

Intervertebral Discs

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

Rib Cage

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

Gender Difference of Pelvis 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

Female vs. Male Pelvis

Female vs. Male Skulls

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

Stress Fracture of the Tibia

STAGES OF BONE REPAIR