Tissues Class 9 Notes CBSE Science Chapter 6

Tissues are a group of specialized cells that possesses similar structure, have a similar origin, and are responsible for performing similar type of functions. In unicellular organisms, the cell is responsible for performing all the vital functions whereas in multicellular organisms different groups of cells are assigned different functions based on the information present in the DNA. These specialized groups of cells are called tissues.

In Chapter 6 Tissue, you will learn the following content:

Introduction to Tissue

The term tissue was coined by Bichat. The study of tissue with the help of a microscope is called Histology. Level of organization in the living system; Cell –> Tissue –> Organ –> Organ System –> Multicellular organism. Based on levels of organization the living system can be divided into;

• Unicellular: Kingdom monera and kingdom Protista
• Multicellular: Kingdom fungi, kingdom Plantae, and kingdom Animalia

Tissues can be divided into two types; Plant tissues and Animal Tissues

Difference between Plant and Animal Tissue

Diference between plant and animal tissue are as follows:

Plant Tissue	Animal Tissue
It mostly consists of dead supportive tissues.	It mostly consists of living tissues.
The tissues are designed to maintain a sedentary lifestyle.	The tissues are designed to maintain a high-mobility lifestyle.
They require less energy to maintain.	They require more energy to maintain.
The tissues get differentiated into meristematic and permanent based on maturity.	No differentiation based on maturity takes place.
The organization is relatively simple.	The organization is relatively complex.

Plant Tissue

A group of specialized cells to perform specific functions in plants are plant tissues. They show the characteristics of growth in specific regions as they are located in those points.

They can be further classified into; Meristematic (dividing) Tissues and Permanent (Non-dividing, specific) Tissues.

Meristematic Tissues

The types of plant tissues in which the cells can divide continuously to enable the plant to grow and increase in length are called meristematic tissues. These types of tissues are found in the growing regions of the plant. They show the following characteristics;

1. They are very metabolically active cells.
2. They have a very thin cell wall.
3. Their vacuole is very small or absent.
4. Their shape can be spherical, oval, rectangle, or even polygonal.
5. The cell cytoplasm is dense with prominent nuclei.

Types: Based on their location these tissues can be categorized into; Apical Meristem, Intercalary Meristem, and Lateral Meristem.

Types of Meristem	Location	Functions	Diagram
Apical Meristem	At the growing tips of stem, root, and axillary buds.	Elongation of root and stem to show primary growth.
Intercalary Meristem	At the stem internodes, and leaf bases.	Forms new cells continuously, and increases the length of a part.
Lateral Meristem	At the lateral sides of the root, stem, and longitudinally below the bark.	Increases the girth of the plant’s body and parts.

Permanent Tissues

The types of plant tissues which have lost their ability to divide and have attained permanent shape, size, and function are called permanent tissues.

They are classified further into; Simple Permanent Tissues, Complex Permanent Tissues, and Protective Tissues.

Simple Permanent Tissues

These permanent tissues are made up of only one type of cells that are similar in structure and function. They are further classified into; Parenchyma, Sclerenchyma, and Collenchyma.

Types	Location	Characteristics	Functions
Parenchyma	Found in the soft parts of the stem, leaves, and roots.	The most common type of living cells are loosely arranged, thin cell walls, and have round or isodiametric shapes.	Stores food, fill spaces, helps in cell-to-cell transport, stores wastes, and maintains the shape and firmness of the body.
Sclerenchyma	Found in the stems around the vascular bundle, veins of leaves, and hard covering of seeds and nuts	They are dead cells with pointy tapered ends, closely packed, and have thickened cell walls by lignin.	It gives strength, rigidity, flexibility, and elasticity to the plant body.
Collenchyma	Found below the epidermis of the dicot stem, veins of leaves, and in non-woody plants.	Consists of living cells, lacks intercellular spaces, cells are elongated, and have irregularly thick cell walls at the corner.	It provides mechanical support, and elasticity to young plants.

Complex Permanent Tissues

Permanent tissues that are made up of more than one type of cells that coordinates to perform common functions like the transport of water, minerals, and food throughout the body. They are further classified into; Xylem, and Phloem.

Types	Location	Characteristics	Function
Xylem	Found in the stem, roots, and leaves	Consists of tracheid, xylem vessels, xylem fibers, and xylem parenchyma.	Dead tubular tracheid and xylem vessels help in the transport of water from root to shoot. Living xylem parenchyma stores food and dead xylem fibers supports the plant body.
Phloem	Found beneath the bark of the plant.	Consists of sieve cells, sieve tubes, companion cells, phloem parenchyma, and phloem fibers.	Living sieve cells and sieve tubes help in the translocation of food throughout the plant’s body. Living companion cells regulates the function of sieve tubes. Living phloem parenchyma stores food and transports food to the non-green part of the plant. Dead phloem fibers provide mechanical support.

Protective Tissues: These permanent tissues protect the plant’s body from any external or internal injury. They are further classified into; Epidermis, and Cork.

Types	Location	Characteristics	Function
Epidermis	Covers the whole outermost layer of the plant’s body.	They have cells that are elongated and flattened with no intercellular spaces between them.	Protects from loss of water and infectious agents.
Cork	Found in the outer bark of woody plants, particularly in trees.	They have cells that are dead, water-resistant, and durable. Also consists of a waxy substance called Suberin that makes the tissue impervious to water and gases	Protects from desiccation, infection, and mechanical injury.

Animal Tissue

Specialized cells grouped to perform specialized functions in animals are called animal tissues. The characteristic feature of these tissues is that they are designed in such a manner that provides the animal with the ability to move and locomotion. They are further classified into; Epithelial Tissues, Muscular Tissues, Connective Tissues, and Neural Tissues.

Epithelial Tissues

These are flat, cuboidal, or column-like cells that cover all the surfaces of the body and help in protection, absorption, secretion, and sensory perception. These cells are tightly packed to appear like sheets. Epithelial tissues are separated from the underlying tissue by an extracellular fibrous basement membrane. They consist of the following types of tissues; Simple squamous, stratified squamous, columnar squamous, ciliated squamous, cuboidal, and glandular.

Types	Location	Characteristics	Function
Simple Squamous	Found in the lining of the mouth, cheek, blood vessels, and esophagus, and forms the alveoli of the lungs.	Thin, flat, and large-sized cells. Forms a single layer.	Helps in the exchange of substances.
Stratified Squamous	Covers the outer surface of the whole body.	Squamous cells are arranged in layers.	Protects the inner tissues.
Columnar	Lines the inner surface of the stomach and intestine.	Tall, cylindrical, pillar-like cells arranged in a single layer.	Helps in the absorption of nutrients from digested food.
Ciliated Columnar	Lines the inner surface of the trachea, lungs, upper respiratory tract, and buccal cavity.	Columnar cells have hair-like projections called cilia.	Helps in pushing the mucus along with other particles to clear the pathway.
Cuboidal	Lines the kidney tubules as well as the ducts of the salivary glands.	Cube-shaped cells.	Helps in the absorption of useful materials.
Glandular	Found in the stomach, intestines, and pancreas.	Cells are arranged in such a manner that they fold to form glands.	Synthesis and secretion of substances on the surface of the epithelium.

Muscular Tissues

Muscular tissues consist of cells that are elongated, and narrow, and may have stripes called muscle fibers. They are mainly found associated with the skeletal system of the body, however, help in forming organs also. They are responsible for the locomotion and movement of the body. They consist of the following types of tissues; Smooth Muscles, striated muscles, and cardiac muscles.

Types	Location	Characteristics	Functions
Smooth/ Non-striated Muscle Tissues	Found in the iris of the eye, uterus, digestive tract, and other internal organs.	The cells are long, lack stripes, uni-nucleate, have pointed ends, and perform only involuntary action.	Carry out the movement of the visceral organs.
Striated/ Skeletal Muscle Tissues	Found attached to the bones.	The cells are long, cylindrical, unbranched, multinucleate, and performon voluntary actions.	Helps in locomotion and movement of the body.
Cardiac Muscle Tissues	Found only in the walls of the heart	The cells are cylindrical, branched, uni-nucleate, and involuntary.	Helps in rhythmic contraction and relaxation of the heart to pump blood throughout the body.

Connective Tissue

Connective tissues consist of loosely packed cells embedded in the intercellular matrix. Helps to connect various tissues and also provide them cushioning which is why they are mainly found in deeper parts of the body. They consist of the following types of tissues; Proper connective, supportive connective, and fluid connective.

Proper Connective Tissue: Also called loose connective tissue as the cells are scattered, irregularly shaped, and embedded in a soft matrix. They cover all the internal organs of the body and help in binding and supporting to maintain the structure of the body. They are further classified into; Areolar, adipose, and fibrous.

Types	Location	Characteristics	Functions
Areolar Tissue	Found between skin and muscles, wrapped around blood vessels, nerves, and bone marrow.	Cells and irregularly arranged fibers are embedded in a gelatinous matrix.	Helps in strengthening the internal organs.
Adipose Tissue	Found under the skin, wrapped around the internal organs like intestines, and kidneys.	Cells are filled with fat globules.	Helps in cushioning and preventing heat loss.
Fibrous Tissue	Found in the spaces between the bones and muscles	Fiber-forming cells that give rise to tendons and ligaments.	Tendons are responsible for binding muscles to bones. Whereas ligaments are responsible for binding bones to bones.

Supportive Connective Tissues: These are comparatively hard tissues that have fibers and minerals as a matrix. They form the skeletal system of the body. They are further classified into; Cartilage, and Bone.

Types	Location	Characteristics	Function
Cartilage	Found in the nose, external ear pinna, trachea, larynx, ends of the long bones, and in between the vertebrae	The tissue is semi-transparent, non-porous, and elastic.	Provides flexibility, and helps in smoothening the bone ends to prevent friction during movement.
Bone	Found in the skeletal system of the body.	The tissue is very hard, non-flexible, and porous.	Provides shape to the body forming the framework.

Fluid Connective Tissue: Fluid in nature due to the presence of a liquid matrix. They are present throughout the body to help in the transport of materials and gases, and to provide connectivity throughout the body. They are further classified into; Blood, and Lymph.

Types	Location	Characteristics	Function
Blood	Found throughout the body.	Blood plasma forms the fluid matrix in which blood cells like RBC, WBC, and platelets float. Appears red.	Helps in the transport of gases, digested food, hormones, and waste material to different parts of the body.
Lymph	Found between intercellular spaces, spaces between organs, etc. throughout the body.	The pale-colored fluid matrix formed of blood plasma and WBC cells.	Helps in the transport of nutrients, gases, and hormones between blood vessels and other different tissues. Protects the body from infection.

Neural Tissue

These are made of highly specialized cells called neurons that are responsible for the conduction of electrical impulses throughout the body to and from the central nervous system (brain and spinal cord) and sensory systems. They are located throughout the body and get accumulated in the brain, and spinal cord. The neural cells have three parts; the cell body (nucleus and cytoplasm), the axon (transmits impulses from the cell body to the next neuron or other receptors), and dendrites (receive impulses from other neurons or other transmitters).

FAQs on Tissues

1. What are the main functions of tissue in a multicellular organisms?

Answer:

Tissue is responsible for;

1. Maintaining the division of labour in the body.
2. Providing a definite shape and structure to the body.
3. Providing mechanical strength to the body.

2. What is the importance of tissues?

Answer:

Tissue not only enables the division of labour, and specific functions but is also responsible for the formation of different organs, and organ system that is the basis of all higher level multicellular organism’s formation.

3. Which animal tissues are directly responsible for the movement of the body?

Answer:

The animal tissues which are directly responsible for the movement of the body are nervous tissues that gives the stimulation to move and muscular tissue that performs the movement.

4. What do you understand by the term “tissue system”?

Answer:

It means the difference in function of different groups of tissues based on their location in the organism’s body.

5. Define the unit structure of a tissue.

Answer:

The unit structure of a tissue is defined as the group of cells having similar structure and function along with their extracellular matrix that forms the tissue.