Question

Define the term "tissue”.

Answer 1

Hint: These are divided differently in animal tissues and plant tissues and all the tissues present in both animals and plants have important and different functions to perform.

Complete answer:
Tissue is a group of cells or you can say it is a cellular organisational level between cells and a complete organ which are organised to perform various functions.

Animal tissues are divided into four basic types:
> Epithelial tissue: It is formed by cells which cover the surfaces of organs like the surface of skin, the inner lining of the digestive tract etc. These create protective boundaries and these are involved in the diffusion of ions and molecules and helps in absorption of water and nutrients and also help in removal of waste.

> Connective tissue: These tissues are the fibrous tissues which are found in between other tissues everywhere in the body as these are developed from the mesoderm (middle layer). As it is present in the middle, it supports other tissues. It connects, binds or separates other tissues and the organs. These are further of three types- fibrous, skeletal and fluid connective tissues.

> Muscular tissue: It is a soft tissue that composes muscle and provides muscle the ability to contract, this tissue is responsible for the movement in our body. It consists of elongated cells called muscle fibres. These are opposed to the other tissues present in the muscle. These are further of three types- cardiac, smooth and skeletal muscle tissues.

> Nervous tissue: These are the groups of organised cells which are present in the nervous system. Their main function is to receive the impulse and send it to the brain and spinal cord. These are also sent to the muscles via the nerves.

Plant tissues are divided into three types:
- Epidermis: These are the cells which form the outer layer of leaves.
- Vascular tissue: It consists of two components i.e., Xylem and Phloem.
- Ground tissue: It is not that much differentiated if we compare it to other tissues
These can be divided into two basic types:
    - Meristematic tissues: These have actively dividing cells.
    - Permanent tissues: These have groups of living or dead cells formed by meristematic tissue.

Thus, you can define tissue as the group of the cells which are organised to perform various functions and these are divided into different types in animal tissues and plant tissues which have different functions to perform.

Note: Tissues are a group of cells which have similar structure and similar functions and they function together as units. The human body consists of many types of cells and these all are classified into mainly four types of tissues which is epithelial, connective, muscular and nervous tissue.