Tissues

A group of structurally and functionally similar cells performing a particular function is called a tissue.

Four types of elements together make up the xylem tissue. They are:

1. Tracheids — They are thick walled and tubular dead cells. They transport water and mineral.
2. Vessels — They are tubular cells and transport water and mineral.
3. Xylem parenchyma — They store food.
4. Xylem fibres — They are supportive in function.

Following are the functions of the stomata:

1. Exchange of gases with the atmosphere occur through stomata.
2. Transpiration (loss of water in the form of water vapour) also takes place through stomata.

The specific function of the cardiac muscle is to contract and expand. They show rhythmic and involuntary contraction and relaxation throughout life enabling the heart to beat and pump blood to all parts of the body.

Labelled diagram of a neuron is shown below:

(a) Squamous epithelium

(b) Tendons

(c) Phloem

(d) Adipose tissue

(e) Blood

(f) Nervous tissue

1. Skin — epithelial tissues
2. Bark of tree — cork (formed by secondary meristem)
3. Bone — Connective tissue (Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.)
4. Lining of kidney tubule — Cuboidal epithelium (with cube-shaped cells)
5. Vascular bundle — Xylem and phloem (Complex permanent tissue)

The parenchyma tissue can be found in the leaf, fruits, as well as flowers. It is located beneath the epidermis.

The primary role of epidermis in plants is protection. The entire surface of a plant has an outer covering epidermis. It protects all the parts of the plant. Epidermal cells on the aerial parts of the plant often secrete a waxy, water resistant layer on their outer surface. This aids in protection against:

• loss of water
• mechanical injury
• invasion by parasitic fungi

A strip of secondary meristem located in the cortex forms layers of cells which constitute the cork. Cells of cork are dead and compactly arranged without intercellular spaces. They also have a substance called suberin in their walls that makes them impervious to gases and water. This is how cork act as a protective tissue protecting the plants from any physical or mechanical injuries and pathogenic infection.

The completed chart is shown below:

A group of structurally and functionally similar cells performing a particular function is called a tissue.

A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue. In multi-cellular organisms, tissues provide structural and mechanical strength and enables the division of labour. In such organisms, many tissues work together to form an organ and then an organ system.

Types of simple tissue are:

1. Parenchyma
2. Collenchyma
3. Sclerenchyma

Apical meristem is present at the growing tips of stems and roots.

The husk of coconut is made of sclerenchymatous tissue.

The constituents of phloem are:

1. Sieve cells
2. Sieve tubes
3. Companion cells
4. Phloem fibres
5. Phloem parenchyma

Muscular tissue is responsible for movement in our body.

A neuron cell looks like a tree. A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arises. Usually each neuron has a single long part (process), called the axon, and many short, branched parts (processes) called dendrites.

Three features of cardiac muscles are:

1. They are cylindrical.
2. They are uninucleate.
3. They are branched.

Following are the functions of areolar tissue:

1. It fills the space inside the organs.
2. It supports internal organs.
3. It helps in repair of tissues.