(Sample Material) IAS PRE GS Online Coaching : General Science - "Tissue"

Sample Material of Our Online Coaching Programme

Subject: General Science

Topic: Tissue

Tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence a tissue is an ensemble of cells not necessarily identical, but from the same origin, that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues. The study of tissue is known histology.

Animal Tissue

The structure of animal tissue is directly related to its function. Tissue is groups of cells with a basic structure and function. There are four types of tissues.

Type of Animal Tissue

• Epithelial tissue
• Connective tissue
• Muscular tissue
• Nervous tissue.

Epithelical tissue

It is a tissue that is made up of tightly packed cells. Without much materials with in these cells. The reasons for the tightly packed cells are to act as a barrier against mechanical injury, invading micro-organisms and fluid loss. We can define epithetical tissue by considering two points in mind one is the number of cells layers and two the shape of the cells.

(i) On the basis of cell layers

(a) When an epithelium has a single layer of cells it is called a simple epithelium.
(b) Where as a multiple tier of cells are known as stratified epithelium.

(ii) On the basis of simple shape of cells:

Cuboidal : its occurrence is in kidney tubules, salivery glands, inner lining of the cheek. Its main function is to give mechanical strength.

Columnar : its occurrence is in sweat gland, tear gland, salivary gland its main function is to gives mechanical strength concerned with secretions.

Squamous : when it forms a living as that of blood vessels, it is called endothelium. Its main function is to protect the underlying parts from injury, entry of germs, etc.