Describe various types of epithelial tissues
Epithelial tissues Epithelial tissues provide covering to the inner and outer lining of various organs. The cells of epithelial tissues are compactly packed with a little intercellular matrix. There are two types of epithelial tissues: (i) Simple epithelium (ii) Compound epithelium (i) Simple epithelium : Composed of a single layer of cells and functions as a lining for body cavities ducts and tubes. It is further divided into three types on the basis of structure modifications- (a) Squamous epithelium – It is made of a single layer of flattened cells with irregular boundaries. It is found as a lining for body cavities, ducts, and tubes such as in the walls of blood vessels and air sacs of lungs. Functions – It helps in forming a diffusion boundary. (b) Cuboidal epithelium – It is made of a single, layer of cube-like cells. It is commonly found in the ducts of glands and tubular parts of nephrons in kidneys. Specialized cuboidal cells are capable of producing gametes found in gonads called the germinal epithelium. Functions- It helps in secretion and absorption and also in moving particles or mucus in a specific direction over the epithelium. (c) Columnar epithelium – It is composed of a single layer of tall and slender cells. Nuclei are located at the base. Its free surface may have microvilli. It is found inlining of the stomach and intestine. Functions – It helps in secretion and absorption.
