The skeletal system.

Specific Readings:
Behnke: pgs 4-8
Thompson and Floyd: pgs 2-9, 43-55

The skeletal system

Number of bones in the skeleton.

Axial Skeleton:

Appendicular Skeleton

Functions of the skeletal system.

1)      

2)      

3)      

4)      

5)      

Bone can be studied at the following levels:

Organ:

Tissue:

Cellular:

Main cells associated with bone:

Osteocytes:

Osteoblasts:

Osteoclasts:

Structure of Bone:

Osteone:

Haversian Canal:

Lamellae:

Lacunae:

Bone Growth:

Initially as cartilage:

Epiphysis and Epiphyseal Plate

Metaphysis:

Daiphysis:

In the Epiphyseal Layer:

Reserve Layer:

Proliferation Layer:

Hypertrophic Layer:

Calcified Layer:

Two Types of Bony Material:

Cortical:

Cancellous:

Strength of Bone

Strength vs flexibility

Rapid vs slow loads

Macrostructure of bone:

Medullary Cavity:

Endosteum:

Cancellous and Cortical bone:

Periosteum:

Articular (hyaline) cartilage:

Bone is a metabolically active tissue.

1)

2)

3)

Resorption and deposit of bone

·        Use of bone determines density, size, and shape of bone

·        Wolff's Law - Julius Wolff, 1892

·        Bone is constant flux

·        Injury

·        Tennis players

Physical Activity

·        Daily stress

·        Daily loading in elderly

·        Space Flight

Types of loads

1.     Compression

2.     Tension

3.     Shear

4.     Torsion

5.     Bending

·        Injuries occur at very high rates of loading relative to the "condition" level of the bone.

·         Stress fracture

1^st Class Levers

2^nd Class Levers

3^rd Class Levers

Types of bones

1)     long bones

2)     Flat bones

3)     Short bones

4)     Irregular bones

5)     Sesamoid bones

Organization of bone formations also serve specific purposes.

·        Spine – vertebrae organized and fitted to protect spinal cord and maintain upright posture.

·        Rib Cage – ribs, thoracic vertebrae, sternum protect lungs and heart

·        Bones of the foot – foot arches provide absorption of loads

·        Skull – protect brain

·        Pelvis – support internal organs

The interaction of bones with each other are what allows us to perform the wide variety of motions that we under go.  Meetings of two or more bones occur at articulation sites that we call joints.