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Epithelial tissues
Epithelial tissues provide covering to the inner and outer lining of various organs. The cells of epithelial tissues are compactly packed with little intercellular matrix.
There are two types of epithelial tissues :
(i) Simple epithelium
(ii) Compound epithelium
(i) Simple epithelium :
Composed of 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 boundaries.
(b) Cuboidal epithelium – It is made of single , layer of cube-like cells. It is commonly found in ducts of glands and tubular parts of nephrons in kidneys. Specialized cuboidal cells are capable of producing gametes found in gonads called germinal epithellium.
Functions- It helps in secretion and absorption and also in moving particles or mucus in a specific direction over the epithellium.
(c) Columnar epithelium – It is composed of a single layer of tall and slender cells. Nuclei are located at base.
Its free surface may have microvilli.
It is found in lining of stomach and i intestine.
Functions – It helps in secretion and absorption.