Class 9 Tissues NotesNotes Important Questions NCERT Solutions
A group of cells that are similar in structure and perform a particular function is called tissue.
Differences between plant tissue and animal tissue:-
|Plant Tissues||Animal Tissues|
|Most of the plant tissues are dead that provide mechanical support.||Most of the animal tissues are living .|
|Plant tissues consume less energy.||Animal tissues consume more energy.|
|Cell growth in plant tissues is non uniform.||Cell growth in animal tissues is more uniform.|
Types of plant tissues:-
- Meristematic Tissue
- Permanent tissue
- The tissue which is capable of division and responsible for growth in plants is called meristematic tissue.
- Cells of this tissue are very active and have dense cytoplasm.
- They have thin cellulose walls.
- They lack vacuoles.
Types of meristematic Tissue:-
- Apical Meristem
- Lateral Meristem
- Intercalary Meristem
- It is present at the growing tip of stems and roots.
- It is responsible for increase in length of stems and roots.
- It is present at the lateral side of stems and root.
- It is responsible for increase in girth of stems and roots.
- It is present at the base of the leaves or near the nodes.
- It is responsible for increase in length between the nodes.
The tissue having permanent shape, size, function and do not have ability to divide is known as permanent tissue.
Differentiation:- The process of taking up a permanent shape, size and a function by the cells of meristematic tissue to convert into permanent tissue is known as differentiation.
Types of permanent tissue:-
- Simple permanent tissue
- Complex permanent tissue
Simple permanent tissue:-
This type of tissue is composed of same type of cells.
Types of simple permanent tissue:-
- The cells of this tissue are living.
- They are loosely packed.
- They have thin cell walls.
- This tissue provides support to plants and also stores food.
- The parenchyma tissue which contains chlorophyll and perform photosynthesis is called chlorenchyma.
- The parenchyma tissue present in aquatic plant contains large air cavities which help them to float. Such parenchyma is called aerenchyma.
- Parenchyma tissue of stems and roots also stores nutrients and water.
- The cells of this tissue are living, elongated and irregularly thickened at the corners.
- They have very little intercellular space.
- Collenchyma provides flexibility to the plants.
- It also provides mechanical support to the plants.
- They are found in various parts of the plants like tendrils, stems of climbers, leaf stalks below the epidermis etc.
- The cells of this tissue are dead.
- The cells are closely packed.
- It makes the plants hard and stiff.
- The cells are long and narrow and the walls are thickened due to lignin.
- It provides strength to the plants.
- It is present in coconut husk, in stems, around vascular bundles, in the veins of the leaves and in the hard covering of seeds and nuts.
- The outermost layer of cells in plants is called epidermis.
- It is protective layer of plants made of a single layer of cells.
- In desert plants, epidermis is thicker and has a thick waxy coating of cutin to prevent loss of water.
- Epidermal cells of roots produce long hair like parts that increase the surface area for the absorption of water.
➢ As plants grow older epidermis of stem is replaced by a layer of dead cells called cork.
➢ The cells of cork have no or very little intercellular space.
➢ The cells of cork have a chemical called suberin that prevents exchange of gases and water.
The tiny pores present on the surface of the leaves (in the epidermis of the leaves) are called stomata.
Functions of stomata:-
- It helps in exchange of gases.
- It helps in transpiration.
Transpiration:- The loss of excess water in the form of water vapour by the plants is called transpiration.
Complex permanent tissue:-
This type of tissue is made of more than one type of cells.
Types of complex permanent tissue:-
- It consists of tracheids, vessels, xylem parenchyma and xylem fibres.
- The cells have thick walls.
- Many cells of xylem are dead.
- Tracheids and vessels transport water and minerals from roots to different parts of the plants.
- Xylem parenchyma stores food and helps in sideways conduction of water.
- Xylem fibres are mainly supportive in function.
- Phloem consists of sieve tubes, companion cells, phloem fibres and the phloem parenchyma.
- Phloem transports food from leaves to different parts of the plant.
- Phloem cells are living except for phloem fibres.
Types of Animal Tissues:-
- Epithelial Tissue
- Connective Tissue
- Muscular Tissue
- Nervous Tissue
- These are the covering or protective tissues in the animal body.
- It covers most organs and cavities within the the body.
- The cells of epithelial tissues are tightly packed.
Types of epithelial tissue:-
- Simple squamous epithelium
- Stratified squamous epithelium
- Columnar epithelium
- Cuboidal Epithelium
- Glandular Epithelium
Simple squamous epithelium:-
- The cells of this tissue are extremely thin and flat.
- These tissues are present where transportation of substances occurs.
- It is present in lining of blood vessels, lung alveoli, oesophagus and lining of mouth.
Stratified squamous epithelium:-
- Cells of this tissue are arranged in a pattern of layers to prevent wear and tear.
- The cells of this tissue have pillar like structures.
- These tissues are present where absorption and secretion occurs like inner lining of the intestine, respiratory tract etc.
- In respiratory tract, the columnar epithelial tissue also has cilia (hair like projection) which helps to clear mucus. This type of tissue is called ciliated columnar epithelium.
- The cells are cube shaped.
- They are present in the lining of kidney tubules and ducts of salivary glands.
- It provides mechanical support.
- Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is formed. This is glandular epithelium.
- The cells are loosely packed.
- The cells are embedded in an intercellular matrix.
Examples of connective tissue:-
- It has a fluid (liquid) matrix called plasma.
- Red blood cells RBCs, white blood cells (WBCs) and platelets are suspended in plasma.
- Plasma contains proteins, salts and hormones.
- Blood transports gases, digested food, hormones and waste materials.
- It has hard matrix that is composed of calcium and phosphorus compounds.
- It is a strong and non-flexible tissue.
- It forms the framework that supports the body.
- It also anchors the muscles and supports the main organs of the body.
- Ligament connects two bones.
- This tissue is very elastic.
- It has considerable strength.
- It contains very little matrix.
- Tendons connect muscles to bones.
- Tendons are fibrous tissue with great strength but limited flexibility.
- It has solid matrix that is composed of proteins and sugars.
- It has widely spaced cells.
- It is present in nose, ear, larynx, trachea and on the bone surfaces at joints.
- It is found between skin and muscles, around blood vessels and nerves and in the bone marrow.
- It fills the space inside the organs, supports internal organs and helps in repair of tissues.
- It stores fat below the skin and between internal organs.
- The cells of this tissue are filled with fat globules.
- It acts as insulator due to the storage of fat.
- The cells of this tissue are elongated.
- It is responsible for movement in our body.
- Muscles contain special contractile proteins, which contract and relax to cause movement.
Voluntary muscles:- The muscles which can be moved by our conscious will are called voluntary muscles.
These muscles are mostly attached to bones and help in movement so, they are also called skeletal muscles.
Ex:- Muscles of limbs
Involuntary muscles:- The muscles which cannot be moved by our conscious will are called involuntary muscles.
Ex:- Muscles of heart, blood vessels, alimentary canal etc.
Types of muscular tissue:-
- Striated Muscles
- Smooth/Unstriated Muscles
- Cardiac Muscles
- The cells of this tissue are long, cylindrical, unbranched and multinucleate (having many nuclei).
- These are voluntary muscles.
- Ex:- Muscles of limbs
- The cells of this tissue are long with pointed ends (spindle-shaped) and uninucleate (having a single nucleus).
- They are found in alimentary canal, blood vessels, iris of the eye, ureters and in the bronchi of the lungs.
- They are involuntary muscles.
- The cells of this tissue are cylindrical, branched and uninucleate (having a single nucleus).
- These tissues show rhythmic contraction and relaxation throughout life.
- Ex:- Muscles of heart
- The brain, spinal cord and nerves are all composed of the nervous tissue.
- The cells of this tissue are called nerve cells or neurons.
- Nerve cells transmit the information within the body.