Question

Classify and describe epithelial tissue on the basis of structural modifications of cells.

Answer 1

Types of epithelial tissue

There are two types of epithelial tissue mentioned below:

• Simple epithelium- Made up of a single layer of cells.
• Compound epithelium- Made up of two or more layers of cells.

Types of simple epithelium

On the basis of structural modifications, simple epithelium can be classified as:

• Squamous epithelium
• Cuboidal epithelium- Ciliated or glandular
• Columnar epithelium- Ciliated or glandular

Simple epithelium

Simple epithelium consists of only a single layer of cells which lines the body cavities, tubes and ducts.

Types	Description	Location	Function
Squamous epithelium	Single thin layer of flattened cells having irregular boundaries.	Walls of blood vessels, air sacs of lungs.	Formation of a diffusion boundary.
Cuboidal epithelium	Single layer of cube-like cells.	Ducts of glands, tubular parts of nephron.	Absorption and secretion.
Columnar epithelium	Single layer of tall and slender cells with the nuclei located at the base of cells.	Lining of stomach and intestine.	Secretion and absorption.
Ciliated epithelium	Single layer of cuboidal or columnar cells with fine hair-like structures (cilia) at the free surface	Trachea, fallopian tubes.	Movement of fluid or particles in a certain direction.
Glandular epithelium	Single layer of cells with secretory functions.	Salivary glands, goblet cells of the alimentary canal.	Production and release of secretory products.

Compound epithelium

Compound epithelium is made up of more than one layer of cells.

• Types: Keratinised and non-keratinised stratified epithelium is present.
• Location: The moist surface of buccal cavity and pharynx is covered with non-keratinised stratified epithelium. The keratinised stratified epithelium is present in the layers of the epidermis of the skin.
• Functions: Provides protection against mechanical and chemical stress.