Muscles are a type of tissue in your body that is made up of many contractile cells and fibres. These contractile cells effect movement of an organ or part of your body.
"Contractile" cells mean that they are able to shorten in length.
Therefore, when a muscle contracts, the muscle shortens and this, in turn, effects
movement.
A joint is made up of two or more bones that slide around each other to allow
for movement to occur. Many muscles in your body have two attachments. One attachment
is usually on one side of a joint (bone#1) and the other attachment is on the
other side of the joint (bone#2). When the muscle contracts, it can pull bone#1
up while bone#2 stays still (the arrow represents the direction of movement
of bone#1 on bone#2 by this muscle).
