What are some functions of muscles?
Primarily, muscles are responsible for movement - be this lifting your leg or pumping blood. The movement is achieved through paired contraction and relaxation.
There are three main types of muscle which all have different functions. These are:
Skeletal - Also known as voluntary or striated (due to stripes caused by muscle fibrils), skeletal muscles are what we generally think of when discussing muscles. Most are joined to bones by tendons and produce conscious movement, such as moving your arm or walking.
Smooth - Smooth, or involuntary, muscle are responsible for our bodies automatic processes that we are not conscious of. Smooth muscle is commonly found in the walls of hollow organs such as the stomach, intestines and even blood vessels. It is incredibly important as without it, we wouldn't be able to transport substances (vacoconstriction - movement of blood through vessels - and peristalsis - food moving through the digestional tract - are both caused by smooth muscle), or carry out vital functions, such as breathing.
Cardiac This type of muscle forms the walls of the heart and are responsible for it's contraction. It is structurally similar to skeletal muscle, but is controlled by the autonomic nervous system making it involuntary (Thank goodness! - It would be a little difficult to have to remember to make your heart beat!). Cardiac muscle also has the advantage of being very resistant to fatigue.
Hope this helps, let me know if i can do anything else:)