Health Information

A group of cells having the same origin, similar shape and specific or common generalized function is known as a tissue. The tissues are classified into four major groups. They are epithelial tissue, connective tissue, muscular tissue, nervous tissue. These four groups of tissues are called elementary tissues.

Epithelial tissue

Epithelial tissues form the covering or lining to the free surfaces of the body. They perform vital functions like protection, excretion, glandular secretion, and absorption. The epithelial cells contain minimal extra cellular material. But they are arranged on a basement membrane. Epithelium is further classified as simple epithelium and stratified epithelium.

Simple epithelium

It consists of a single layer of cells. It is further divided into Squamous, cubodial, columnar, ciliated, and glandular epithelium.

Squamous (or pavement) epithelium

It consists of flat cells arrangement edge to edge as in a mosaic. This type of epithelium covers the alveoli of lungs, pericardial, pleural and peritoneal cavities.

Cubodial epithelium

Here, the cells are cubical. They are arranged over a basement membrane. It is found in the distal convoluted tubules of the kidney.

Columnar epithelium

It consists of tall, pillar like cell arranged on a basement membrane. It is found in lungs and ducts of glands.

Ciliated epithelium

The cells may be cuboid or columnar. But they contain hair like structures called cilia present in the free border, e.g. cells lining the trachea.

Glandular epithelium

It consists of cylindrical or columnar cells. It is present in secretory glands like salivary glands and breast. The glands are of two types unicellular and multicellular. The multicellular glands are again classified as endocrine glands and exocrine glands. The endocrine glands which do not contain a duct and they secrete hormones. The exocrine glands which contain a duct and they secrete enzymes.