LESSON 2
TISSUES OF THE BODY
Section I. GENERAL
2-1. DEFINITION
A tissue is a grouping of like cells working together.
2-2. TYPES OF TISSUES
There are several major types of tissues. The most common types are epithelial,
connective, muscle, and nervous tissues. Later, this lesson will discuss each type.
2-3. TISSUES AND ORGANS
a. Tissues make up organs. An organ is a structure performing a particular
function. An organ is composed of several different tissues. Examples of organs are
the lungs and the heart.
b. In some cases, a term may be used to describe both a type of tissue and a
kind of organ. For example, we speak of bone tissue and of bones. We speak of
muscle tissue and of muscles.
Section II. EPITHELIAL TISSUES
2-4. DEFINITION
Epithelial tissue is tissue that covers surfaces and lines cavities. Here, it may
protect, absorb, and/or secrete. Epithelial tissue covers the outer surface of the body.
It lines the intestines, the lungs, and other hollow organs.
2-5. TYPES OF EPITHELIAL CELLS (BY SHAPE)
Figure 2-1 illustrates the basic types of epithelial cells by shape. The three basic
shapes are squamous (flat), cuboidal (cubes), and columnar (columns).
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