Tissues Class 9 Notes
Tissues: These are the cluster of structurally and functionally similar cells arranged and designed.
1. Meristematic tissue
The growth of plants of only in certain specific regions. This is because the dividing tissue also known as meristematic tissue are present in specific regions only. This tissue is also called growth tissue and is found in the growing regions of the plant like root and shoot tip.
The different types of meristematic tissues are:
(i) Apical meristem
These are present at growing tips of stems and roots. Thus, are helpful in increasing the length of the stems and the roots. It acts as pro-meristem having actively dividing cells, giving rise to other meristems.
(ii) Intercalary meristem
These are present at the base of the leaves or internodes (on either side of the node) of twigs. It helps in longitudinal growth (elongation) of plants.
(iii) Lateral meristem (cambium)
These are present on the lateral sides of stem and roots. It helps in increasing the girth of the stem or root.
2. Permanent tissue
This tissue is formed from the cells of meristematic tissue when they loose their ability to divide and have attained a permanent shape, size and function by the process called differentiation.
Different types of permanent tissue:
I. Simple permanent tissue
It is made up of only one type of cells.
Characteristics of parenchyma are as given below:
•These are simple living cells with little specialisation and thin cell wall.
• Cells are usually loosely packed with large spaces between cells (intercellular spaces).
Functions of parenchyma are as follows:
• It serves as food storage tissue.
• This tissue provides support to plants.
• When the parenchyma cell contains chlorophyll in some situations, it performs photosynthesis. Such type of parenchyma tissue is called chlorenchyma.
• In aquatic plants, large air cavities are present in parenchyma cells in order to give buoyancy to plants, which help them to float. Such type of parenchyma tissue is called aerenchyma.
• Parenchyma of stems and roots also stores nutrients and water.
Characteristics of Collenchyma are as given below:
• Cells are living, elongated and irregularly thickened at the corners.
• They have very little intercellular spaces.
Functions of Collenchyma are as follows:
• It provides mechanical support and elasticity (flexibility) to plants.
• It also allows easy bending in various parts of a plant (leaf and stem) without breaking.
Characteristics of sclerenchyma are given below:
• The cells of sclerenchymatous tissue are dead.
• Cell walls are thickened due to lignin (a chemical substance) deposition, which acts as cement and gardens them.
• Due to the presence of thick walls, there is no internal space between the cells.
Functions of Sclerenchyma are as follows:
• It is known to be the chief mechanical tissue, which makes plant hard and stiff, e.g. husk of coconut is made up of sclerenchymatous tissue.
• It forms protective covering around seeds and nuts. It gives rigidity, flexibility and elasticity to the plant body.
II. Complex permanent tissue
It is made up of more than one type of cells gaming a common origin.
Types of complex permanent tissue are:
The cells of xylem have thick walls and many of them are dead. It is responsible for the transport of water and minerals from roots to other parts of the plant.
Xylem consists of various types of elements, which are as follows:
• These are dead, long, tubular structures with tapering ends.
• They transport water and minerals vertically.
• Long, tube-like structures, formed by a row of cells, placed end to end.
• These are also dead cells with lignified walls.
• They also help in conduction of water.
(c) Xylem Parenchyma
• These are only living cells of xylem with thin cell walls.
• It stores food and helps in the sideways conduction of water.
(d) Xylem fibres
• They are elongated dead cells with tapering ends and thick cell walls.
It transport food from leaves to other parts of the plant. Materials can move in both directions in it. All phloem cells are living except phloem fibres.
Phloem is made up of following for types of elements:
• They are tubular cells with perforated walls.
• They have thin layer of cytoplasm.
On the basis of the functions they perform, animal tissues are classified into four basic types namely epithelial, connective, muscular and nervous tissue.
The covering or protective tissues in the animal body are epithelial tissues. It is the simplest protective tissue of the animal body, which covers most organs and cavities of the body. It forms a barrier to keep different body systems separated from each other.
On the basis of shape of the cells and their arrangement, epithelial tissues are further classified as:
(i) Squamous Epithelium
The skin, which protects the body, is also made of squamous epithelium. It is further categorised as:
(a) Simple Squamous Epithelium
• The cells are very thin and flat and appear as tiles over a floor. It is single-layered and closely fitted.
• It forms a delicate lining of blood vessels and lung alveoli, where substance transport occurs through a selectively permeable membrane.
(b) Stratified Squamous Epithelium
• Cells are arranged in many layers to prevent their wear and tear.
• It is found in the outer side of skin as it is highly resistant to mechanical injury and is water-proof.
(ii) Cuboidal Epithelium
• It forms lining of kidney tubules and ducts of salivary glands, where it provides mechanical support. It also forms geminal epithelium of gonads.
(iii) Columnar Epithelium
• It is usually found in the inner lining of intestine, where absorption and secretion occur.
(iv) Ciliated Columnar Epithelium
• It is found in the respiratory tract and also lines oviducts, sperm ducts, kidney tubules, etc.
(v) Glandular Epithelium
Functions of Epithelial tissue
(i) It protects the underlying cells from dying, injury, infections and also from harmful effects of chemicals.
(ii) It plays a vital role in regulating the exchange of materials between the body and external environment and between different body parts.
(iii) It helps in absorption of water and nutrients and in diffusion of gases.
2. Connective tissue
This tissue is s problem specialised to connect various body organs with each other, e.g. it connects two or more bones to each other, muscles to bones, binds different tissues together and also gives support to various parts of the body. The cells of connective tissue are loosely packed, living and are embedded in an intercellular matrix that may either be jelly-like, fluid, dense or rigid in nature. The nature of matrix differs in concordance with the function of the particular connective tissue.
Various types of connective tissues are:
It is a fluid connective tissue that links different parts of the body and helps to maintain the continuity of body. It contains fluid matrix called plasma and blood cells such as RBC’s (Red Blood Corpules or Cells), WBC’s (White Blood Corpules) and platelets suspended in it. Plasma also contains proteins, salts and hormones. Blood transports nutrients, gases, hormones and vitamins to various tissues of the body and carries excretory products from tissues to excretory organs. It also conducts heat and regulates body temperature. Properties shown by different blood cells in the body are as follows:
• RBCs: Help in transport of respiratory gases, oxygen and carbon dioxide with the help of haemoglobin to and from the various parts of our body.
• WBCs: Fight with diseases by producing antibodies.
• Blood platelets: Help in the clotting of blood.
It is very strong and non-flexible tissue. It is porous, highly vascular, mineralised, hard and rigid. Its matrix is made up of proteins and is rich in salts of calcium and phosphorus.
It forms the framework that supports the body. It also anchors the muscles and supports the main organs.
They connect one bone to other bone. A ligament is very elastic and had considerable strength.
They are strong and inelastic structures which join skeletal muscles to bones.
(v) It is a specialised connective tissue having widely spaced cells. It has solid matrix, which is composed of proteins and sugars. Cartilage provides smoothness to the bone surfaces at the joints. It is present in the nose, ear, trachea and larynx.
(vi) Areolar tissue
It is located between skin and muscles, around blood vessels and nerves and in the bone marrow. It is a loose and cellular tissue. It is a supporting and packing tissue found between the organs lying in body cavity. It fills the space inside the organs, supports internal organs and helps in repair of tissues.
(vii) Adipose tissue
It is located below the skin and in between the internal organs. It serves as a fat reservoir and keeps visceral organs in position, acts as an insulator due to the storage of fats.
3. Muscular tissue
It consists of elongated cells, called muscle fibres. This tissue is responsible for the movement in our body.
It contains special type of proteins called contractile proteins, which causes movement of Muscles by contracting and relaxing.
Different types of muscular tissues are:
(i) Striated muscles
(ii) Unstriated muscles or smooth muscles
(iii) Cardiac muscles
Comparison between the structures of different types of muscular tissues
|Shape of cell||Long cylindrical and unbranched.||Long with pointed ends and unbranched.||Cylindrical and branched.|
|Number of nuclei||Multinucleate.||Uninucleate.||Uninucleate.|
|Position of nuclei within cell||Mainly at the periphery of the cell.||Present centrally in cell.||Centrally located.|
4. Nervous tissue
The cells of nervous tissue are highly specialised for recieving stimulus and then transmitting it very rapidly from one place to another within the body itself. They are called the nerve cells or neurons. They enable the cells to respond according to the stimuli recieved. Brain, spinal cord and nerves are composed of nervous tissues.
An individual nerve cell may be upto a metre long and is composed of three major parts:
(i) Cell body: It consists of cytoplasm, nucleus and cell membrane.
(ii) Axon: It is a single long conducting fibre extending from neurone. It transmits impulse away from the cell body.
(iii) Dendrites: These are short branched fibres of neuron, which recieve nerve impulses.
Difference between plant tissues and animal tissues
|Plant Tissues||Animal Tissues|
|In plants, dead supportive tissues are more abundant as compared to living tissues.||In multicellular animals living tissues are more common as compared to dead tissues.|
|They require less maintenance energy as they are autotrophic and can make their own food.||They require more maintenance energy as they are heterotrophic and they have to move in search of food.|
|There is a differentiation of tissues into meristematic and permanent tissues, which are localised in certain regions of planet based on their dividing capacity.||Such differentiation is absent in animals as their growth is uniform.|
|Due to activity of meristematic tissue plants continue to grow throughout life.||Animals do not show growth after reaching maturity. Reparative growth is, however, present.|
|Organisation of plant tissues is simple.||Organisation of animal tissues is complex with the development of more specialised and localised organs and organ systems.|
|Tissues organisation is meant for stationary habit of plants.||Tissues organisation is targeted towards high mobility of animals.|
Try To Solve These Questions
Q1. Name the different types of meristematic tissues?
Q2.Name Various types of connective tissues?
Q3. What is Tissue?