Class 9 Science Chapter 6: Tissues Important notes and Points

CBSE Class 9 Science Tissues Important Notes and Points
Important Notes of Plants and Animal Tissues

 Tissue:A group of Cells having similar structure and performing same function is called Tissue

Plants and Animal differ in their way of life

• Plants are fixed or stationary whereas animals move in search of food and shelter
• Plants are autotrophs,where as animals depend on others for their food
• Plants growth continue throughout the life of plants in specific region,where as growth in animals is uniform
• Animals have highly specialised organs and organ system

Plant and animal tissues are different in their structure as they have different way of life

• Plant tissues are mainly supportive as plants are fixed
• Most of the plant tissues consist of dead cells to provide mechanical strength
• Animals move around in search of food and shelter, therefore most of their tissues are living and active
• being active and motile, animals need more energy as compared to plants

Plants tissues can be broadly classified into two types

1. Meristematic Tissue
2. Permanent Tissues

Meristematic Tissues: There are also known as dividing tissues. They are present in specific region in the plant body where growth continues throughout life On the basis of region, Mersitem can be divided into three types

1. Apical Meristem:They are present at tip of shoot and root, it helps in the increase of length of plant body
2. Lateral Meristem: Theya re present on the sides, parallel to the long axis of root and stem, it increases width or girth of the plant
3. Intercalary Meristem: It is present at the base of leaves and the internodes of grasses, It increases the length ofinternodes

Characteristics of Cells present in Meristematic Tissues
1.They have thin cell walls
2.Their cytoplasm is dense
 3.They have prominent nuclei
4.Vauoles are absent

How Permanent Tissues are Formed
 New cells produced by meristem are initially like those of meristem itself, but as they grow and mature, their characteristics slowly change and they become differentiated as components of other tissues.
They take up a specific role and lose the ability to divide. As a result, they form a permanent tissue. This process of taking up a permanent shape, size, and a function is called differentiation. Cells of meristematic tissue differentiate to form different types of permanent tissue.

Cells of permanent tissues have thin or thick cell wall, their nucleus is small in relation to cell size and protoplasm is present on periphery with big central vacuole

Permanent Tissues can be further divided into two types

1.Simple Tissues:These Tissues are composed of one type of cells
2.Complex Tissues:These are composed of more than one type of cells

Types of Simple Permanent Tissues

1.Parenchyma:It is a basic packing tissue, which provides support to plants and also stored nutrients.

• Parenchyma cells are least specialised 
• It consists of living cells having thin cell wall, composed of cellulose
• They are loosely packed with large intercellular spaces
• It stores reserve food in the form of starch
• It also stores nutrients, water and waste products in stems and roots
• In leaves and young stems parenchyma cells may contain chloroplats, such parenchyma is called chlorenchyma..It performs photosynthesis
• In aquatic plants, fairly large air cavities are present to provide buoyancy , it is called aerenchyma

Collenchyma: It is a strong and flexible simple tissue to provide mechanical strength and flexibility

• It consists of living cells having, cell wall thickened due to deposition of pectin
•  Intercellular spaces are absent
• cells are elongated in shape, irregularly thickened at the corners
• There is little to no intercellular spaces
• It is present in young stem and leaf stalk
• It provides mechanical strength and elasticity to growing stems
• The stems can stand bending or swaying by wind or passing animals

Sclerenchyma:It is a simple Tissue to provide protection and mechanical strength

• It consists of dead cells after it becomes mature
• It is hard and rigid due to deposition of lignin in cell walls
• Intercellular spaces are absent
• Sclerenchyma cells are of two types fibres and sclereids
• Fibres are long and narrow and pointed
• Fibres occur in stem and leaves around the vascular tissue
• Sclereids are short,isodiametric

Epidermis:It is the outermost layer of cells around entire surface of plant body

• Epidermal cells are flat with thick outerwalls and side walls
• They form continuous layer lacking inter cellular spaces
• In aerial parts of plants these cells secrete waxy water resistant layer of cutin on their outer surface
• It protects against loss of water by transpiration and mechanical injury and attack by parasitic fungi
• Desert plants may have multilayered epidermis with very thick layer of cuticle

Leaf Epidermis has tiny pores called Stomata

• Stomata are enclosed by two kidney shaped guard cells through which exchange of gases and transpiration take place
• Root epidermis has hair like extensions of epidermal cells.
• They increase the surface area of absorption of water and salts
• In old stem cork cambium is formed in place of epidermis
• Bark Develops due the activity of cork cambium
• It consists of layers of tightly packed cells
• These cells form cork at maturity
• Cell walls of cork cell contain suberin which makes it impervious to water and gases

Complex Permanent Tissue phloem and Xylem are complex permanent tissue in plant body.Xylem conducts water and minerals, where as phloem translocates food

.Xylem and Phloem together constitute vascular bundle

Xylem:It consists of four types of cells
 1.Tracheids
2.Vessels
3.Xylem Parenchyma
4.Xylem Fibres

Tracheids and vessels are the main conducting element in xylem

• Both are living and tubular cells
• The wall is highly thickened with lignin,except at certain circular spots known as pits
• Tracheids and vessles also provide mechanical support in addition to conduction of water and mineral from roots to different parts of plant body
• This process is known as ascent of sap
• This conduction takes place in one direction only
• Tracheid has tapering ends
• A vessel has cylindrical tube like structure placed one above the other
• Xylem parenchyma helps conduction sideways
• Xylem fibres are non living thick walled cell providing mechanical support

Phloem:Phloem is complex tissue consists of four types of cells

1.Sieve Tubes
2.Companion Cells
3.Phloem parenchyma
4.Phloem Fibres

• Phloem Consists of Both living and non living cells
• Sieve tubes are tubular cells with perforated cell walls


• Phloem transports food material from leaves to different parts of the plant body


• Transport of food material through phloem takes place in both direction

Animal Tissues are of four types
1.Epithelial
2.Connective
3.Muscular
4.Nervous

Epithelelial tissue; It Forms a protective covering around the body and lines most of the organs and cavities within the body

• Cells of Epithelelila tissues are tightly packed to form a continous sheet
• They have negligible amount of packing material between them
• Intercellular spaces are lacking
• Sheets of epithelila tissue lie on a layer of fibrous extracellular substance called basement membrane
• Blood capilllaries and nerve cells reach up to basement membrane

Epithelial Tissue are classified into

1.Squamous epithelium consists of flat cells arranged like tiles

• Cells are very thin and form a delicate layer
• Lining of blood capillaries help in exchange of material between blood and body tissues
• Lining of alveoli in the lungs helps in exchange of gases

Cuboidal Epithelium Consists of Cubical cells having nucleus in the centre

• Lining of kidney tubules is cubiodal epithelium, which helps in filtration of blood and urine
• Lining of ducts of salivary glands has cubiodal epithelium  to give mechanical support

Columnar epithelium:It consists of tall colum like or pillar like cells.Lining of stomach and intesntine helps in absorption and secretion of material

Stratified Epithelium or compound Epithelium has cells arranged in several layers
1.lining of mouth and oesophagus consists of several layer of squamous epithelium
2.Skin consists of several layers of kerantinised squamous epithelium to protect against mechanical injuries

Epithelial tissues are variously modified for their function

Ciliated Epithelium consists of cuboidal or columnar cells having hair like projections on the outer surface.lining of nasal passage has ciliated epithelium.Movement of cilia helps in clearing mucus from nasal passage

Glandular epithelium performs the function of secretion
 lining

• lining of stomach has some cells, which secrete mucus and enzymes
• Lining of small intestine is folded inwards to form multicellular glands.

Connective tissue: It connects or binds other tissues and cells of the body

• A connective tissue consists of living cells loosely scattered in a non living intercellular matrix
• Matrix may be jelly like,fluid or rigid depending on the function it performs

Connective Tissues can be further divided into
1.Blood:Blood is a connective tissue consisting of fluid matrix called plasma. blood transports nutrients, respiratory gases, excretory products and hormones.It protect against diseases and regulates body temperature.Here are components of blood

• Plasma contains proteins, salts and hormones. Blood cells are of three types
• Erythrocytes-Red blood cells.It contains haemoglobin which binds with oxygen
• Leucocytes-White blood cells.They help in fighting germs
• Thermobocytes-Platelets-They help in clotting of blood

Bone:It consists of dense and rigid matrix. Bones form a framework of the body. It supports the body and its organs

• Bone is a strong and non flexible tissue
• Bone cells are embedded in a hard matrix around longitudinal canals
• Matrix has deposition of calcium and phosphorous 

Cartilage:It is a non porous flexible tissue

• Cartilage cells are scattered in group of 2, 3, or 4 cells
• Matrix has deposition of proteins deposition of proteins and sugars
• Fibres form a delicate network.
• Cartilage is found in nose ear trachea and larynx
• It provides support and flexibility to body parts and makes the surface of joints smooth.

Areolar Connective Tissue;It is most widely distributed in the body

• It has jelly like matrix with white and yellow fibres
• Cells are loosely scattered in the matrix
• It serves as packing and supporting tissue between organs, ;present between skin and muscles, around blood vessels and nerves, in the bone marrow.
• It also helps in repair of tissues

Adipose Tissue: It is present between the skin

• It has same structure as areolar tissue
• Adipocytes are the main cells for storage of fat globules
• It gives shape to the body and acts as an insulator

Ligaments are strong and elastic, fibrous tissue.

• They contain little matrix, which has yellow fibres.
• Ligaments connect bones to bones

Tendons are tough and non elastic fibrous tissue

• They contain little matrix, which has white fibres.
• Tendons connect muscles to bones and muscles to muscles.

Muscular Tissue;It has elongated muscle cells, which are specialised for contraction and relaxation
Muscular tissues are of three types
1.Skeletal muscles:They are attached to bones and help in body movements

• Skeletal muscle cells are long cylindrical unbranched and multinucleate
• They have alternate light and dark bands or striations,therefore called striated muscles
• Movements of these muscles are under the control of our will therefore they are called voluntary muscles
• They get tired on sustained use.

Visceral muscles are present in the visceral organs i.e, alimentary canal iris of eye, ureters and bronchi of lungs.

• Visceral muscle cells are long spindle shaped pointed at both uninucleate.
• They lack striations,therefore called unstriated or smooth muscles
• Movement of these muscles are not under the control of our will, therefore they are called involuntary muscles
• They do not get fatigued

Cardiac Muscles; They are present in the heart

• Cardiac muscle cells are cylindrical branched and uninucleate.
• They have indistinct striations
• They are immune to fatigue.
• They have intercalated discs which help in transmission of wave of muscle contraction from one cardiac muscle fibre to next

Nervous Tissue: It is specialised for receiving the stimuli and then transmitting them very rapidly as electrical impulses.

• Nervous tissue is present in the brain, spinal cord and nerves.
• Cells of this tissue are called nerve cells or neurons
• A nerve cell may extend upto one metre in length
• A neuron consists of expanded cell body called cyton containing nucleus and cytoplasm
• It has several thin highly branched fibres called dendrons, which carry impulses towards cyton.
• It also has a long thick unbranched fibres called axon, which carries impulses away from cyton.

A collection of nerve fibres enclosed in a layer of connective tissue forms a nerve.