BACKGROUND:
There are four basic types of tissues recognized in
higher animals, epithelial, connective, muscular and nerve. This
activity focuses on muscle tissue. Students should complete
the worksheet before you compare and contrast the different types of muscle
cells.
A muscle is a tissue that performs different functions which
cause some sort of movement to take place. There are three different
types of muscle cells: skeletal, smooth, and cardiac. The various muscles
of our bodies serve as the engines or powerhouses of the body and are so
constructed to provide speed and power. Each muscle cell is designed
for various functions that are needed by a certain area in the body. Muscle
tissue has the ability to contract or to shorten, thus producing movement
of internal and external body parts. Breathing, speaking, walking,
talking, eating, and almost every other function requires muscle tissue.
Smooth muscles are composed of elongated, spindle shaped cells
and are commonly involved in involuntary motions. Involuntary muscle contractions
or motions are those movements that cannot be consciously controlled. The
nucleus is centrally located and there are no striations in smooth muscle
cells. These types of cells are located throughout the body.
Muscles made from these types of cells include those found in the walls
of blood vessels, urinary bladder, and the digestive system.
Skeletal muscles allow movement by being attached to bones in
the body. Skeletal muscles control voluntary movements which can
be consciously controlled. Skeletal muscles are made up of cylindrical
fibers which are found in the locomotive system. The nucleus of each
cell tends to be toward the edge of each cell and the cells are striated.
Cardiac muscles are roughly quadrangular in shape and have a
single central nucleus. The cells form a network of branching fibers.
The muscles are cross striated and are involuntary. The muscles are
found in the heart.
Muscle tissues are supplied with nerve fibers that carry messages
to and from the central nervous system (brain and spinal cord).
Muscles are composed of about 75 per cent water, 20 per cent protein, and
about 5 per cent is made up of carbohydrates, lipids, inorganic salts,
and nonprotein nitrogenous compounds. The composition does vary in
the different muscles.
PROCEDURE:
- Give students worksheet on the three types
of muscle tissues.
- Make sure that students know what they are observing.
For example, give them guidelines for shape of cells; where the nucleus
would be; what is a striations; location of the tissue in the human body;
and whether the tissue is voluntary or involuntary
