What are the types of epithelial tissues?
There are majorly 4 types of epithelial tissues:
(i) Simple squamous epithelium
This type of epithelium has flat cells lying upon the basement membrane. Also known as ‘pavement epithelium’, it is used to diffuse substances across membranes and perform filtration. This epithelium is present in the thinnest surfaces such as the lining of blood capillaries and alveoli and in the inner lining of the mouth.
Simple squamous epithelium
Several layers of the squamous epithelium, stacked one above the other form the outermost layer of the skin, are known as stratified squamous epithelium. Thanks to the multiple layers, it prevents the wear and tear of the upper surface of the skin.
Stratified squamous epithelium
- Columnar epithelium
This epithelium has a tall, pillar-like structure which gives it a ‘column-like appearance.’ and hence the name columnar epithelium.
The tall cells help to carry out absorption or secretion and can be located in the
intestine’s inner lining.
Columnar epithelium
Sometimes the cell surfaces of the columnar epithelium may have tiny hair-like projections called cilia. These cilia carry rhythmic movements to move certain non- motile substances. Thus, the ciliated columnar epithelium is found to cover the lining of the respiratory tract. It throws out foreign particles trapped in mucus, which enter the respiratory tract. It is also found in the fallopian tubes of the ‘female
reproductive system’, where the cilia help to propel the ovum in the forward
direction
Cilia
- Cuboidal epithelium
Cuboidal epithelium is made up of cube-like cells. They provide mechanical support. They are found lining the kidney tubules, in the thyroid, and the ducts of salivary glands.
Cuboidal epithelium
- Glandular epithelium
Sometimes epithelial cells attain the capacity to secrete important substances in the body. These are formed by inward folds in the cuboidal cells. The cells are called gland cells, and the tissue is called glandular epithelium.
They are located in the parts involved in secretions, like the salivary glands, mucus glands, and glands secreting ear wax.
