Smooth Muscle is the type
of muscle tissue that is located in the walls of all the hollow
organs of the body (except the heart). The contraction of smooth
muscle reduces the size of these
structures it surrounds.
Therefore, it can (among other things):
- Regulate the flow of blood in the arteries;
- Move food through the gastrointestinal tract;
- Expel urine from your
- Expel the foetus from the uterus;
- Regulate flow of air through the lungs.
The Structure of Smooth Muscle:
Smooth muscle tissue is made up of thin-elongated
muscle cells, fibres. These fibres (muscle
cells) are pointed at their
ends and each has a
Each cell is filled with a specialised cytoplasm (called
and is surrounded by a thin cell membrane called the sarcolemma.
has many myofibrils which
lie parallel to one another in the direction of the long axis of the
However, the cells/fibres of smooth muscle are not arranged
in a definite striped (striated) pattern, as in the case of skeletal
muscles - hence the name
Smooth muscle fibres interlace to form sheets or layers of muscle tissue
rather than bundles.
Smooth muscle is involuntary tissue - as it is
not under concious control by the brain.
Other types of muscle tissue:
There are three main types of muscle tissue.
Muscle - muscles that move bones (under
Muscle - surrounding organs and other body structures (unconcious
Muscle - the specialised muscle found only in the heart.