Epithelial and connective tissues are vital tissues of the body and among the four types of tissues. Epithelial tissues are present just below the basement membrane, whereas connective tissues are found all around the body along with the nervous system.
There are three epithelial tissues based on the shape and organization of layers of cells. Based on shape, epithelial tissues can be simple columnar and cuboidal tissues. Based on the organization of layers of cells, tissues can be grouped into simple epithelium or stratified epithelium.
Each connective tissue differs from others based on three segments; cell or lymph, ground, and fibers substance.
Comparison Chart
| Basis for Comparison | Epithelial Tissues | Connective Tissues |
| Definition | Epithelial tissues are thin tissues, cover all the exposed skin of the body. | Connective tissues connect, support, bind, or separate other tissues or organs. |
| Originated from | Develops from the endoderm, mesoderm, or ectoderm from the embryological germ layer. | Develops from the mesoderm |
| Arrangement | Arranged in layers which may be either single or multi-layer | In scattered form in the matrix and without any arrangement |
| Surrounded by | Does not surrounded by blood capillaries | Surrounded by blood capillaries |
| Location | Lie above the basement membrane | Lie below basement membrane called lamina propia |
| Nutrition | Gain their nutrition from the cellular membrane | Gain nutrition from the blood capillaries |
| Bounded by | Special protein, desmosomes and hemidesmosomes | Blood capillaries and materials (elastic or collagen fibers |
| Site | Lungs, kidneys, skin and mucus membrane | Bones, nerves, ligaments, tendons and blood) |
What are Epithelial Tissues?
Epithelial tissues are found in the arranged pattern below the basement membrane. The free surface is exposed to the air and fluids, whereas the bottom layer is attached to the basement membrane. They originate from embryological germ layers, which can be from the endoderm, i.e., from the lining of the GIT, from ectoderm, i.e., from the epidermis and the mesoderm, i.e., from the inner linings of the body cavities. Skin epithelial tissues are derived from the ectoderm. Epithelial tissues have many cells tightly packed together. The epithelial tissues act as a barrier to microorganisms.
The upper surface of the epithelium is exposed to air or fluids while the bottom surface is attached to the basement membrane. The epithelial tissue plays as a barrier to microorganisms. The free surface of the epithelium is visible to air or fluids while the bottom is closed to the basement membrane. The epithelial tissue acts as a blockade to microorganisms.
Types of Epithelial Tissues
Epithelial tissues are categorized into three groups based on size, shape and arrangement; columnar epithelium, squamous epithelium, and cuboidal epithelium. In columnar epithelium, the cells are like columns. In the squamous epithelium, the cells are flattened and scale-like, whereas, in the cuboidal epithelium, the cells are in a cube shape.
The epithelium tissues can be grouped into two types based on the number of layers; simple or stratified epithelium and multilayer epithelium. Simple epithelium is only one cell thick, whereas the multi epithelium is two or more cells thick. Simple epithelium is present below the basement membrane and is in direct contact with the basement membrane. It also separates the underlying connective tissues.
Functions
Epithelial tissues perform various vital functions in the body. They mainly form a covering of the organs, internally as well as externally so involved in the protection of the cells. Epithelial cells help in transcellular or intercellular transportation.
Epithelium tissues are also involved in selective absorption, excretion and secretion. Hormones and enzymes are secreted by the epithelial cells in the glands. Epithelial cells in the intestine absorb the nutrients, whereas kidney epithelial cells excrete wastes. Epithelial cells in the ear, nose, tongue and skin perform the role as a sensory organ. Epithelial cells in respiratory and reproductive tracts drive substances like dust particles and female gametes, respectively.
Epithelial tissues are also found abundantly in cell junctions, so help in the cell to cell communication, cell junction acts; as the main communication point between tissue cells and plasma membrane.
What are the Connective Tissues?
Connective tissues have wide networking of nerves and blood capillaries. These are in scattered form in the matrix and does not show any specific pattern. These are bounded within the matrix of elastic, cartilaginous and collagen tissue. Fibroblast is the most common among all. Others are plasma cells, mast cells, adipocytes and leukocytes.
Types of Connective tissue
Connective tissues are present in blood, adipocytes, cartilage, bone, fibrous connective tissue, reticular connective tissues and loose connective tissue.
The connective tissues are vital components of almost all organs in the body. These tissues support and anchor other tissues and organs help in the muscles and bone formation and the working of the blood and lymph.
The connective tissues are also responsible for distributing oxygen and nutrients throughout the tissues as in the case of blood. These are responsible for the formation and organization of the skeleton, fat, blood, nerves and muscles. They also function not only to support and protect but binding of the other tissues to promote a way for communication and transport. Besides, the adipose connective tissues are responsible for providing heat to the body.
Key Differences between Epithelial and Connective tissues
- Epithelial tissues are composed of cells and a small amount of intercellular matrix, whereas connective tissues are composed of the cells and a huge amount of intercellular matrix.
- Epithelial tissues are developed from the endoderm or mesoderm or ectoderm from the embryological germ layer, whereas connective tissues are developed from the mesoderm.
- The arrangement of the epithelial cells is either single or multilayer, whereas cells of connective tissues are in scattered form in the matrix.
- Epithelial tissues are not supported by the blood capillaries, whereas connective tissues are supported by the blood capillaries.
- Epithelial tissues line above the basement membrane, whereas connective tissues lie below the basement membrane.
- The cells of epithelial tissues get their nutrition from the cellular membrane, whereas the cells of connective tissues get their nutrition from the blood capillaries.
- Epithelial tissues are bounded by the special proteins, desmosomes and hemidesmosomes, whereas connective tissues are bounded by the blood capillaries and other materials such as elastin or collagen fibers.
- Epithelial tissues can be found in the lungs, kidneys, skin and mucus membrane, whereas connective tissues are found in bones, nerves, ligaments, tendons and blood.
Conclusion
In conclusion, epithelium tissues are present just below the basement membrane, whereas connective tissues are present in all organs of the body. Both differ in their types and functions.