KS3 Biology Part 2: Skeletal System

Skeletal System

• The human skeleton has several different functions:

-Support
-Protection
-Movement
-Production of red blood cells

• Joints and Muscles

-Bones in the skeleton are held together in joints.
-Joints allow the skeleton to move.
-Joints are held together by ligaments.
-The end of each bone is covered in cartilage for a smooth surface that cushions the joint.
-The joint is filled with a fluid that lubricates the joint.

• Muscles and Force

-Muscles move joints.
-Muscles are attached to bones by tendons.
-End joint needs two muscles to make it work. This is called an antagonistic pair.
-One muscle moves the joint in one direction. The other moves the joint in the opposite direction.
-Muscles work by contracting and getting shorter in length. This pulls the bone and moves the joint.
-The force exerted by the muscles can be measured in Newtons.
-To work out the force applied by a muscle multiply the mass lifted by its distance from the joint.
-The answer is mass x distance from joint equals force x distance from the same joint.