Osteology

Functions of the Skeleton1. Protection

Protect vital and delicate soft-tissue structures from injury. Skull and the rib cage.

2. SupportThe skeletal system provides the support

necessary to safely maintain an upright posture.

3. MovementBones 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 BonesDivided into five groups.

1. Long bones2. Short bones3. Flat bones4. Irregular bones5. Sesamoid bones

Long Bones

Primarily serve as levers.FemurHumerusRadius UlnaTibia Fibula

Short Bones

Wrist and ankleTend 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.SpinePelvisOssicles 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 BoneEvery 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 SkeletonThe 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 SkeletonsMale 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 JointsClassified into three major groups or types.1. Synarthroses (immovable joints)2. Amphiarthroses (slightly moveable joints)3. Diarthroses (freely movable joints)

DiarthrosesOften 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 socket2. hinge joints3. condyloid or ellpsoid joints4. saddle joints5. pivot joints6. gliding joints