When you talk about cells, the first thing that should come to your mind, as biology students is, “what kind of a cell is it?” Is it a plant cell or an animal cell? Both these different types of cells have basic differences. And again, the animal cells are classified into different types based on their function, structure and some other factors. Epithelial tissue is one such animal tissue. Let us learn about the types of epithelial tissue.
What is Epithelial Tissue?
Epithelial tissues are animal tissues. These tissues show the characteristics of animal cells. Here the cells are eukaryotic with a nucleus and have membrane-bound organelles. A cell wall is absent in animal cells. This lack of cell walls gives the animal cells flexibility. The cells of the tissue can take up different shapes to become specialized and perform specific functions.
Epithelial tissue is called as the epithelium. The tissue generally has a free surface and faces the body fluid inside or the outside environment. Epithelial tissues largely are covering tissues or tissues that line the inner lining of organs in the body. The intercellular matric is very less as the cells are compactly packed.
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Types of Epithelial tissue
Broadly, there are two types of epithelial tissue – the simple epithelium and the compound epithelium. In a simple epithelial tissue, there is a single layer of cells. It is generally found in the limning o the body cavities or organs or even ducts and tubes.
The compound epithelial tissue consists of two or more layers of cells. They form stratified layers. In the skin, they have a protective function. They do not have much of a role in absorption and secretion. Their function is to provide protection against any form of mechanical or chemical stress. The compound epithelium can be found on the dry surface of the skin, buccal cavity, pharynx, the lining of the salivary glands ducts and pancreatic ducts.
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Based on the structure, shape, size, and arrangement of cells, we further classify types of Epithelial Tissue. They are:
- Squamous Epithelium – These are thin, flat cells that are closely packed, with irregular boundaries. The squamous epithelial cells line the cavities of the mouth, oesophagus, alveoli, blood vessels and air sacs of lungs.
- Cuboidal Epithelium – These cells are cuboidal in shape. They are found in the salivary glands, tubular parts of nephrons in kidneys, sweat glands etc. Their main function includes absorption, secretion, and excretion.
- Columnar Epithelium – The columnar epithelium has cells that are pillar-like and column-like. The nuclei of the cells are located at the base. The free surface may have microvilli. They are present in the lining of the stomach and intestine. Its functions include absorption and secretion.
- Ciliated Epithelium – When the columnar epithelial tissues have cilia, then they are called the ciliated epithelium. Their main function is to move particles or mucus in a specific direction. The rhythmic movement of the cilia helps in the movement of material in one direction. This tissue is found in the inner surface of organs like bronchioles and fallopian tubes.
- Glandular Epithelium – These are modified columnar epithelial tissues. They are large cells that present in the tear glands, sweat glands etc. Their main function is secretion. The glandular epithelium can have either unicellular cells or multicellular cells with a cluster of cells. According to the mode in which they pour their secretions, the glands again divide into exocrine and endocrine glands.
Solved Questions For You
Q: Where do you find the ciliated epithelium in the animal body?
Ans. Ciliated Epithelium is a type of Epithelial Tissue. The ciliated epithelium is found in the inner lining surface of the fallopian tubes, bronchioles etc. The ciliated epithelium cells are columnar epithelial cells with cilia. Their main function is to help in the movement of material in one direction.