Functions of the Skeleton 1. Protection Protect vital and delicate soft-tissue structures from injury. Skull and the rib cage.

2. Support The skeletal system provides the support necessary to safely maintain an upright posture. 3. Movement Bones serve as points of attachment for muscles. As muscles contract, bones act as levers. Joints serve as pivot points that allow actual movement.

Classifications of Bones Divided into five groups. 1. Long bones 2. Short bones 3. Flat bones 4. Irregular bones 5. Sesamoid bones

Long Bones

Primarily serve as levers. Femur Humerus Radius Ulna Tibia Fibula

Short Bones

Wrist and ankle Tend to be cube shaped and are generally found in areas which only very limited motion is required. Principle function is to provide strength.

Flat Bones

Consist of parallel, platelike layers of hard or compact bone. Provide large areas for muscle attachment. Protection.

Irregular Bones

Bones that have obvious peculiarities in their shape are placed in this classification. Unique in appearance and function. Spine Pelvis Ossicles of the ear.

Sesamoid Bones

Small and rounded and triangular bones usually develop within the substance of tendons and fascial tissue. Found adjacent to joints. Named after their resemblance to sesame seeds.

Features of a Typical Bone Every bone in the skeleton is a unique organ – a distinct structural unit. Long bones uniformly possess many of the features of bones in general.

Organization of the Skeleton The 206 bones of the adult skeleton are grouped into two subdivisions: 1. Axial Skeleton (80) bones. 6 tiny middle ear bones 74 bones that form the upright axis of the body Skull, vertebral column, and thorax (sternum and ribs)

Appendicular skeleton (126 bones) Form the appendages and the girdles that attach them to the axial skeleton. Shoulder girdles, arms, wrists, hands, hip girdles, legs, ankles, and feet.

Differences Between Male and Female Skeletons Male skeleton is larger and heavier. The male pelvis is deep and funnel-shaped, the female pelvis is shallow, broad, and flaring. Bones of the male lower extremity tend to be longer.

Classification of Joints Classified into three major groups or types. 1. Synarthroses (immovable joints) 2. Amphiarthroses (slightly moveable joints) 3. Diarthroses (freely movable joints)

Diarthroses Often called synovial joints. Characterized by the presence of a closed cavity between the bones that make up the joint. Functionally the most important. Most complex structure and are most vulnerable to injury.

Six varieties of diarthrotic joints. Classified according to the shapes of the articular surfaces between bones. 1. ball and socket 2. hinge joints 3. condyloid or ellpsoid joints 4. saddle joints 5. pivot joints 6. gliding joints