The muscular system functions through muscle contraction. Skeletal muscles work with bones to allow movement by contracting and pulling on bones. Smooth muscles, like those in the digestive tract, contract independently to move food and circulate blood. Muscles connect to bones via tendons, with one end serving as the origin point and the other as the insertion point. Skeletal muscles work in pairs as flexors and extensors to both move parts of the body and keep them rigid.

1. Functions of the Muscular
System

2. The main function of the muscular system is
contraction.
A muscle is the tough, elastic tissue that makes body
parts move through contraction. Together with the bones,
we use skeletal muscles to make various movements like
walking, jumping, swimming or bending. It is the muscle
that provides the pulling power on the bones so that we can
move around.
However, even withoout the help of bones, smooth
muscles can move by alternately contracting and relaxing.
Smooth muscles help in performing body activities
necessary for growth and health. For example, muscles in
the digestive tract that help move food through the stomach
and intestines. Muscles in the heart and in the blood
vessels make the blood circulate.

3. How Skeletal Muscles Connected to Bones?
Muscles are softer and more flexible than the bones.
However, the bones and muscles are connected so that the
body can move.
You observed that the muscle fibers are held together
by connective tissue. The ends of most skeletal muscles
are joined to bones by a tendon. It is a tough, flexible
connective tissue. You can feel a somewhat hard but
elastic structure at your heels. That is called the achilles
tendon.
You must have noticed that the two ends of a muscle
tissue seem to have pointed ends. One end of the muscle
is attached to a bone that does not move when the muscle
contracts. This end of the muscle is called origin. The
other end is called the point of insertion. It is attached to a
bone that moves when the muscle contracts.

4. How The Skeletal Muscles Work?
Skeletal muscles contract and pull on the bones to which they are attached
when a nerve stimulates them.
When a person stands erect, many skeletal muscles contract to make the
body rigid. The skeletal muscles also can make one part of the body move
while another part stays stiff.
Skeletal muscles act both ways because they work in pairs. One muscle of
each pair is called the flexor. It bends a joint. The other muscle, the extensor,
does the opposite.
For example, the biceps muscle in the front of the upper arm is a flexer.
When this muscle contracts, the elbow bends and the forearm and hand move
towards the shoulder.
The triceps muscle in the back of the upper arm is an extensor. When it
contracts, the elbow straightens and the forearm and hand move away from the
shoulder. At the same time, the biceps relaxes so the triceps can pull it back to
its original length.