Chapter 6 Tissues (Plant and Animal Tissues) Notes
Welcome to Class 9 Tissues notes Notes for Chapter 6.The topics in this page are What are tissues ,Importance of tissues,Classification of tissues,Plant Tissues,Animal Tissues, Epithelial Tissue,Muscular Tissue,Connective Tissue and Meristematic Tissues. This is according to CBSE and the NCERT textbook. If you like the study material, feel free to share the link as much as possible.
A group of cells similar in structure that work together to perform a particular function forms a tissue.
All types of tissues have two basic components:
Cells: having common origin and function.
Inter-cellular substances: Are nonliving, fibrous, jelly-like substances.
Importance of tissues
Formation of tissues has brought about division of labour in multicellular organisms.
Tissues become organized to form organs and organs into organ systems.
Workload of individual cell ahs decreased due to origin of tissues.
As a result of improved organization and higher efficiency, multicellular organisms have higher survival.
Classification of tissues
Tissues are broadly classified as
animal tissues and
Plant tissues can be broadly divided into two main types. These are
Meristematic tissue and
A meristematic tissue constitutes a group of actively dividing cells present in the growing region of plant, e.g., the tips of roots and stems.
These tissues are responsible for increasing the length and girth of the plant.
Characteristics of meristematic tissues:
The cells of the meristematic tissue are similar in structure and have thin cellulose cell walls.
The cells may be spherical, oval, polygonal or rectangular in shape.
The cells of tissue are compactly arranged and do not have intercellular space.
The cells have dense protoplasm with prominent nuclei.
Vacuoles in these cells are either small or absent.
On the basis of their position in the plant body, meristematic tissues are classified into three types: -
These are present at the tips of roots, shoots, branches and leaves.
It brings about the elongation of the root and stem. It results in increase in the hight of the plant, which is called primary growth.
These are present along the lateral side of the stems and roots. For example: cork cambium.
It causes the organ (stem or root) to increase in diameter and girth. This is called secondary growth.
They are located at the base of leaves or internodes, e.g., stems of grasses and other monocots and below the nodes (e.g., mint).
It produces an increase of length of organ such as leaves and internodes.
Functions of Meristematic tissue
Meristematic tissue acts as a parent tissue from which other tissues develop.
These tissues take part in growth by formation of new cells.
The place of injury in plants is healed up by the formation of new cells by meristems.
A permanent tissue is a group of cells, which is derived from the meristematic tissues, but these cells have lost the power of division temporarily or permanently. Note: The development process by which cells which have been derived from meristematic tissue, take up a permanent shape, size and function is called differentiation.
Permanent tissues are of two types: -
simple permanent tissue and
complex permanent tissue
Simple permanent tissues:
These tissues are composed of cells which are structurally and functionally similar. These tissues are of three types:
Parenchyma forms the bulk of plant body. It consists of thin walled living cells.
The cells are isodiametric, i.e., equally expanded on all sides.
The cell wall is thin and encloses a dense cytoplasm which contains a small nucleus and a large central vacuole.
The intercellular spaces are abundant.
The parenchyma is present in all the organs of the plants, i.e., roots, stems, leaves, flowers, fruit and seeds.
Function of Parenchyma
The main function of parenchymatous tissue is storage of food, e.g., starch in the parenchyma of cortex of potato tuber.
Parenchyma forms the framework of all the plant organs and tissues like cortex. Pith etc.
Parenchyma serves as packing tissue to fill the spaces between other tissues.
It stores waste materials of plants such as gum, crystals etc.
The intercellular air spaces of parenchyma cells allow gaseous exchange.
If chloroplast is present, the parenchyma tissue is called chlorenchyma and it performs photosynthesis.
In aquatic plants, large air cavities are present in parenchyma to give buoyancy to the plants to help them float. Such a parenchyma type is called aerenchyma.
Collenchyma is usually found in 3-4 layers beneath epidermis in stem, petioles and leaves of herbaceous dicot plants.
The cells of this tissue are living, elongated and irregularly thickened at the corner.
In collenchymas, intercellular spaces are generally absent.
Functions of Collenchyma
It provides the mechanical support, protection, flexibility and elasticity to the plants organs.
It allows easy bending in various parts of the plant (leaf, stem) without breaking.
When cells of collenchymas contain some chloroplasts, they manufacture sugar and starch.
Sclerenchyma cells are dead cells and they are devoid of protoplasm.
They are long and narrow as the walls are thickened due to lignin, such cell walls are called lignified.
The cells of sclerenchyma are closely packed without intercellular spaces.
Cells of sclerenchyma are of two types: fibers and sclereids.
Fibers consist of very long, narrow, thick and lignified cells. Sclereids are irregular shaped.
This tissue is present in stems, around vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts. Husk of coconut is made of sclerenchymatous tissue.
Functions of Sclerenchyma
The sclerenchyma is mainly mechanical and protective in function.
It gives strength, rigidity, flexibility and elasticity to the plant body and, thus, enables it to withstand various strains.
Complex Permanent Tissues:
The complex tissue consists of more than one type of cell having a common origin. All these cells coordinate to perform a common function.
Complex tissues are of two types: Xylem or wood and phloem or bast.
Xylem and phloem are both conducting tissues and also known as vascular tissues; together both them constitute vascular bundles.
Xylem is a vascular and mechanical tissue.
Xylem is composed of cells of four different types:
Sieve tubes are slender, tube like structures with perforated walls.
Companion cells are living parenchymarous cells lying on the sides of the sieve tubes.
Sieve tube and companion cells have close cytoplasmic connection with each other through fine pits.
Phloem fibres are thick walled fibres with simple pits.
Phloem parenchymas are thin walled, living cell of parenchyma of phloem.
Function of Phloem:
Phloem transports (conducts) photosynthetically prepared food materials from the leaves to the storage organs and later from storage organs to the growing regions of the plant body.
Protective tissues are a part of plant tissue system. Protective tissues include
It is the outermost protective layer of plant organs.
The epidermis is usually made of a single layer of cells.
Cells of epidermis are elongated and flattened, without intercellular space. They are living cells but their inner contents are similar to parenchyma cells.
In leaves, epidermis bears small pores called stomata.
In some plants living in very dry habitats, the epidermis may be thicker since protection against water loss is critical.
Functions of Epidermis:
The function of epidermis is the protection of plant from injury and infection.
Cuticle of epidermis also helps to reduce water loss by evaporation to prevent dessication.
Stomata present in the epidermis allow gaseous exchange to occur during photosynthesis and respiration.
It also facilitates transpiration.
Cork (or phellem):
Cork cells are dead cells without having intercellular spaces.
They appear at the periphery of roots and stems when they grow older and increase in girth.
They also have a chemical called suberin in their walls that makes them impervious to gases and water.
Functions of Cork:
The function of cork in plant body is to provide protection. It protects plants from external injury and infection.
It also prevents dessication.
Since cork does not catch fire easily, it is used for insulation, shock-absorber, linoleum.
It is also used for making sports goods, such as shuttle-cock, table tennis paddles, crcket balls, etc.
On the basis of the structure of cells and their function, animal tissues are classified into four major types:
The covering or protective tissues in the animal body are animal tissues.
The cells of this tissue are tightly packed and it forms continuous sheet. Indeed cells of epithelium contain very little or no intercellular matrix.
The skin and lining of buccal cavity, blood vessels, alveoli of lungs and kidney tubules are made of epithelial tissue.
Epithelial cells lie on a delicate non-cellular basement membrane which contains a special form of matrix protein, called collagen.
Functions of Epithelial Tissue:
Epithelial cells protect the underlying cells from mechanical and chemical injuries and bacterial or viral infection.
It covers most organs and cavities within the body. It also forms a barrier to keep different body system separate.
Epithelial tissues help in absorption of water and nutrients
Epithelial tissues help in elimination of waste products.
Some epithelial tissues secrete secretion, such as sweat, saliva etc.
Note: Epithelial tissue may be simple, i.e., composed of a single layer of cells, or stratified, i.e., made up of several layers of cells.
Types of epithelial tissue
Depending upon the shape and function of the cells, the epithelial tissues are classified as follows:
Differences between different types of epithelial tissues:
Muscular tissue constitutes all the muscles of the body of an animal.
Muscle cells are elongated and large sized, so they are called muscle fibres.
Muscle cells are typically arranged in parallel arrangement allowing them to work together effectively.
This tissue is responsible for movement in our body. Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.
On the basis of their location, structure and function, there are following three types of muscle fibers:
Striated muscles (stripped, skeletal or voluntary muscles)
Smooth muscles (unstriated, visceral or involuntary muscles)
A tissue which is specialized to transmit messages in our body is nervous tissue. Brain, spinal cord and nerves are all composed of nervous tissue.
Nervous tissue contains highly specialized unit cells called nerve cells or neurons.
These cells are specialized for the conduction of impulse over great distance at great speed.
A neuron consists of a cell body (cyton or soma) with a nucleus and cytoplasm, from which long thin hair- like parts arise called dendrons.
Dendrons further branched out to form dendrites. From the distal part of cyton arises a very long process called axon.
Functions of :
The nervous tissue is responsible for the reception and transmission of information between different parts of the body.
The dendrites receive impulses and the axon takes impulses away from the cell body.
The connective tissue is specialized to connect and anchor various body organs. As such, it connects one bone with another and a bone with a muscle.
Three components are present in all the connective tissues. These are intercellular medium, connective tissue cells and fibers.
The cells of connective tissue are loosely spaced and embedded in an intercellular matrix. The matrix may be jelly like, fluid, dense or rigid.
The nature of matrix decides the function of connective tissue.
Connective tissue binds other tissues together in the organs.
Connective tissue also provides the structural framework and mechanical support to different tissues.
It is also concerned with body defense, fat storage, repair etc.
The main functions of connective tissue are binding, supporting and packing together different organs of the body.
Types of connective tissue:
In animals, there are following five types of connective tissues:
Areolar (loose) connective tissue
Dense connective tissue
Adipose connective tissue
Fluid connective tissue
Aerolar (loose) connective tissue:
It is a loose and cellular connective tissue. Its matrix consists of two kinds fibers: white collagen fibers and yellow elastic fibers.
Aerolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow.
It fills the spaces between different tissues and organs, hence called packing tissue.
Functions of Aerolar
It acts as supporting and packing tissue between organs lying in the body cavity.
It provides rapid diffusion of oxygen and nutrients from blood vessels.
It helps in repair of tissues after an injury.
It helps in fighting foreign antigen and toxin.
Dense connective tissue:
It is a fibrous connective tissue. It is characterized by ordered and densely packed collection of fibers and cells.
It is the chief component of ligaments and tendons.
Ligaments: These are elastic structures made up of yellow elastic fibrous tissue s which connect bone to another. It has considerable strength. Ligaments contain very little matrix. Ligaments strengthen the joint and they prmit normal movement but prevent over-flexing or over-extension. Sprain is caused by excessive pulling (stretching) of ligaments.
Tendons: Te dons are cord like, strong inelastic structures that join skeletal muscles to bones. They are composed of white collagen fibrous tissue.
It has great strength but its flexibility is limited.
It consists of large number of oval and rounded adipose cells (adipocytes) filled with fat globules.
The adipose tissue is abundant below the skin, between the internal organs (e.g., around the kidney) in yellow bone marrow.
Functions of Adipose tissue:
It serves as a fat reservoir.
Adipose tissue acts as food reservoir by storing fat.
It acts as an insulator and regulates body temperature.
Skeletal connective tissue forms the endoskeleton of the body of vertebrates. It includes cartilage and bone.
Fluid connective tissue:
Fluid connective tissue links the different parts of the body and maintains continuity in the body. It includes blood and lymph. Blood:
Blood is fluid connective tissue. In this tissue cells move in a fluid or liquid matrix or medium called blood plasma.
The blood plasma does not contain protein fibres but contain cells called blood corpuscles or blood cells. These blood corpuscles and cells are:
Red blood corpuscles (RBC) or erythrocytes
White blood corpuscles (WBC) or leucocytes
RBCs and WBCs are living, while plasma and platelets are non-living.
Here is the Tissues class 9 notes Summary
Tissue is a group of cells similar in structure and function.
Plant tissues are meristematic or permanent.
Meristematic tissue is the dividing tissue present in the growing regions of the plant
Meristematic tissue becomes permanent tissue when it stops dividing. Permanent tissues are classified as Simple and complicated tissues.
Simple tissues include parenchyma, collenchyma, and sclerenchyma. Xylem and phloem are complicated tissues.
Animal tissues include epithelial, connective, muscular, and nervous.
Epithelial tissue is squamous, cuboidal, columnar, ciliated, or glandular.
Areolar, adipose, bone, tendon, ligament, cartilage, and blood are all connective tissues.
Striated, unstriated, and cardiac are three types of muscle tissue
Neurons transmit impulses in nervous tissue.
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