Objective Demonstrate how the skeletal system enables us to move.Science Concept The way bones are held together, at the joint determines the kind of movement.

The Skeletal System Helps Us Move

MotivationMove your arms up and down. Move them clockwise and then

counterclockwise.Move your legs up, down, and

around.1. Why can you move your arms and

legs in different ways? 2. Are there parts of your body you

cannot move in different directions?

The JointsThe bones in your body are held together at different places.

The place where two bones meet and come together is called a joint.

The way bones are held together at the joint determines the kind of movement you can make.

Ball and Socket joint Pivot joint

Hinge joint Saddle joint

Conyloid joint Gliding joint

Ball and Socket joint

Your shoulder bone and arm bone meet to form a movable joint. Ball and socket joints allow movement in different directions.

Ball-and-socket joints are a special class of synovial joints that enjoy the highest freedom of motion in the body thanks to their unique structure. The shoulder and hip joints are the only ball-and-socket joints in the human body due to the need for great motion at the end of the body’s limbs and the vast amount of musculature needed to move and support such flexible joints.

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Pivot Joint The joint in your head is a pivot joint.

It allows you to turn your head while the other bones in your body do not move.

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Hinge Joints Let bones move back and forth. Your

lower joints and your elbow joints are examples of hinge joints.

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Gliding JointsThe small bones of the wrist slide over each

other. The joint that connects the lower arm to the hand is a gliding joint.

(Look at the joint that connects the lower leg to the foot. In what way is it similar to the wrist?)

Your backbone runs the length from the base of your skull down to the hips. The backbone is made of separate bones stacked one on top of the other and joined by gliding joints.

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Saddle JointA saddle joint is more versatile

than either a hinge joint or a gliding joint. It allows movement in two directions. The saddle joint gives the human thumb the ability to cross over the palm of the hand.

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Conyloid Joints. These joints are similar to ball-and-

socket joints, just without the socket (the "ball" simply rests against another bone end).

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EVALUATION

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