A tissue is a group of cells that have a similar shape
and function. Different types of tissues can be found in different
organs. In humans, there are four basic types of tissue: epithelial,
connective, muscular, and nervous tissue. There may be various sub-tissues
within each of the primary tissues.
Epithelial tissue covers the body surface and forms the lining
for most internal cavities. The major function of epithelial tissue
includes protection, secretion, absorption, and filtration. The skin
is an organ made up of epithelial tissue which protects the body from dirt,
dust, bacteria and other microbes that may be harmful. Cells
of the epithelial tissue have different shapes as shown on the student's
worksheet. Cells can be thin, flat to cubic to elongated.
Connective tissue is the most abundant and the most widely distributed
of the tissues. Connective tissues perform a variety of functions
including support and protection. The following tissues are found
in the human body, ordinary loose connective tissue, fat tissue, dense
fibrous tissue, cartilage, bone, blood, and lymph, which are all considered
There are three types of muscle tissue:
skeletal, smooth, and
cardiac. Skeletal muscle is a voluntary type of muscle tissue that
is used in the contraction of skeletal parts. Smooth muscle is found
in the walls of internal organs and blood vessels. It is an involuntary
type. The cardiac muscle is found only in the walls of the heart
and is involuntary in nature.
Nerve tissue is composed of specialized cells which not only
receive stimuli but also conduct impulses to and from all parts of the
body. Nerve cells or neurons are long and string-like.
In tissues the simplest combination is called a membrane, or
a sheet of tissues which cover or line the body surface or divide organs
into parts. Examples include the mucous membrane which lines body
cavities. Tissues combine to form organs. An organ is a part
of the body which performs a definite function. The final units of
organization in the body are called systems. A system is a group
of organs each of which contributes its share to the function of the body
as a whole.
- Use the worksheet to go over the four tissues
of the Human Body. Make them take notes about each of the tissues
and have them research where these tissues may be in the human body.
- Make sure that the students realize that tissue is made
up of cells.
- Students should look at their own cells of their skin, and
ask them if they can see the entire tissue. Remember the skin is
epithelial tissue. Students should use a Swift-GH microscope
to focus on the different parts of their skin. They can look at their
leg, hand, arm, or palm. They will notice that the shape of the cells
vary considerable from one area of the body to another.
Make them think they may find some tissue, so they look at different
parts of their skin. Review with them that there are different skin
cells at different locations. They cannot find tissue because they
are just look at the surface part of the skin.