1 SIMPLE EPITHELIAL TISSUE
This is the type of epithelial tissue having single layer of cell different types of simple epithelial tissues are squamous columnar cuboidal columnar ciliated and cuboidal ciliated epithelium
(a) squamous epithelial is situated on the basement membrane and it consists of one layer of flat cells nucleus is usually placed in the centre the cells appear like the tiles on the floor (pavement) the squamous epithelium is found in lungs bowman capsule heart inner wall of the blood vessels etc the squamous epithelium of the lungs blood vessels and lymphatics is known as endothelium similary in the heart this epithelium is called endocardium squamous epithelial cells may also help in filtration exchange of gases and other substances from the blood
(b) columnar epithelium is composed of a single layer of cells the height of which is more than its breadth this type of epithelium is found in the alimentary canal lungs and the ducts of glands goblet cells of large intestine (alimentary canal) which secrete mucus is also columnar epithelium columnar cells help in absorption and secretion of various substances
(c) cuboidal epithelium is formed of one layer of cubical cells which have the same dimension from all sides cubical cells are found in bronchioles salivary glands thyroid gland etc they protect the organ and help in secretion of various substances
(d) ciliated epithelium cells of ciliated epithelium may be columnar or cubical in shape they consists of about 15-25 hair like structures on the cell which are known as cilia in some cells cilia are not present and they are known as non ciliated cells are found in the respiratory tract the fallopian tubes and the central canal of the spinal cord ciliary movement helps in the flow of mucus suspended particles and bacteria
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