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
urinary bladder;
- 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
single,
large,
oval nucleus.
Each cell is filled with a specialised cytoplasm (called
sarcoplasm)
and is surrounded by a thin cell membrane called the sarcolemma.
Each cell
has many myofibrils which
lie parallel to one another in the direction of the long axis of the
cell.
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.
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.
They are:
- Skeletal
Muscle - muscles that move bones (under
concious control).
- Smooth
Muscle - surrounding organs and other body structures (unconcious
control).
- Cardiac
Muscle - the specialised muscle found only in the heart.
This Section consists of short summaries about the
structures that form the muscles of the body.
This list is not exhaustive but is intended to be appropriate for students
of A-Level Human Biology, ITEC courses in massage and related subjects,
and some other courses in Health Sciences.
For more general information about Muscles see
the pages about: Anterior
Muscles, Posterior
Muscles, Facial
Muscles, Terminology
about Muscles, and the Structure
of Muscles. |
