Types Of Epithelium Tissue

Definition Of Epithelium Tissue

It is, therefore, the tissue lining the outer surfaces of the body, cavities, hollow organs, and also glandular tissue. It plays a significant role in protection, absorption, secretion, and sensation in the human body.

The cells of the epithelial tissue are very packed with no intercellular material or finely dispersed. It indicates polarity with defined apical and basal surfaces. These two are tightly attached to a basement membrane, meant to provide structural support, avascular—that is, lacking blood vessels—and a high capacity of renewal that has an enabling capacity for quick repair.

Classification Of Epithelium Tissue

The classification of epithelium tissue is listed below-

Based On Cell Layers

• Simple epithelium: A single layer of cells, suited for processes such as diffusion, filtration, and absorption. Examples include the lining of blood vessels and the alveoli of the lungs.

• Stratified epithelium: Many layers protect against abrasion and mechanical stress; found in those areas subject to wear and tear like the skin, mouth, and oesophagus.

• Pseudostratified Epithelium: This epithelium appears to be made of many layers. This is only an appearance and it is caused by the change in the position of the nuclei. It is composed of a single layer of cells. It is present in the respiratory tract where it assists in the expulsion of mucus from the body.

Based On Cell Shape

• Squamous Epithelium: Thin, flattened cells, like scales, move out of the way to enable fast diffusion and filtration. This type can be located in the alveoli of the lungs and lining the blood vessels.

• Cuboidal Epithelium: These are cube-shaped cells engaged in secretion and absorption. They are normally found in glands and kidney tubules.

• Columnar Epithelium: Of high column-like stature, they are specialized for absorption and secretion. They line the stomach, intestines, and parts of the respiratory tract.

• Transitional Epithelium: Specialized in stretching and changing its shape, this kind is found in the urinary bladder, which enables the organ to dilate and contract itself according to requirement.

Functions Of Epithelium Tissue

• Protection: These protect the basic structures from mechanical injury, dehydration, and invasion by pathogenic organisms. The classic examples are the skin and lining of the mouth.

• Absorption: Some epithelial tissues are specialised to absorb various substances. This occurs in the intestines, where food is absorbed, and in the lungs, where oxygen is absorbed.

• Secretion: The glandular epithelium produces and secretes various substances like enzymes, hormones, and mucus. This is noted in certain glands like the thyroid and salivary glands.

• Excretion: The epithelial tissues help in excreting waste products. For example, the epithelium lining inside the kidneys filters waste from blood to form urine.

• Sensory Reception: Some epithelial tissues are specialised with sensory receptors to respond to various stimuli; for example, epithelial cells lining the taste buds and in the skin perform the function of detection of sensation.

Recommended video on "Types Of Epithelium Tissue"