Class 9 Science Chapter 6 Tissues Notes

9 Class Science Chapter 6 Tissues Notes

Textbook	NCERT
Class	Class 9
Subject	Science
Chapter	Chapter 6
Chapter Name	Tissues
Category	Class 9 Science Notes
Medium	English

Class 9 Science Chapter 6 Tissues Notes. here we will be learn about Tissue , Plant Tissue , Animal Tissue , Plant Tissue , Meristematic Tissues , Primary Meristem , Apical Meristem , Intercalary Meristem , Lateral Meristem , Permanent Tissues , Simple Permanent Tissues (Supporting tissue and protective tissue) , Epidermis , Stomata , Cork , Simple Permanent , Parenchyma , Idioblast , Chlorenchyma , Aerenchyma , Collenchyma , Selerenchyma , Complex Permanent Tissue , Xylem , Phloem , Cartilage , Bone , Animal Tissues , EPITHELIAL TISSUE , MUSCULAR TISSUE , Striated muscles , NERVOUS TISSUS , Cardiac muscle fibres etc.

Class 9 Science Chapter 6 Tissues Notes

Chapter - 6
Tissues

Tissue
- Plant Tissue
- Animal Tissue

Plant Tissue
- Meristematic Tissues
  - Primary Meristem
  - Apical Meristem
  - Intercalary Meristem
  - Lateral Meristem
- Permanent Tissues
  - Simple Permanent Tissues (Supporting tissue and protective tissue)
  - Epidermis
  - stomata
  - Cork
- Simple Permanent
  - Parenchyma
  - Idioblast
  - Chlorenchyma
  - Aerenchyma
  - Collenchyma
  - Selerenchyma
- Complex Permanent Tissue
  - Xylem
  - Phloem
Cartilage
Bone

Animal Tissues
- EPITHELIAL TISSUE
- MUSCULAR TISSUE
- Striated muscles
- NERVOUS TISSUS
- Cardiac muscle fibres

Tissue :-

A group of cell that are similar in structure and work together to achieve a particular function is called Tissue.

Plant Tissue
Animal Tissue

Histology :-

The microscopic study of tissue is called Histology.

PLANT TISSUE :-

Plant Tissues are of two types

Meristematic Tissues
Permanent Tissues

Meristematic Tissue (growth tissue) :-

These are simple living tissues having thin walled compactly arranged immature cells which are capable of division and formation of new cells.

Main features of Meristematic tissues are :-

Thin primary cell wall (cellulosic).
Intercellular spaces are absent (compact tissue).
Generally vacuoles are absent, dense cytoplasm & prominent nuclei are present.
Actively dividing cells are present in growing regions of plants e.g., root & shoot tips.

Classification of Meristematic Tissues on the Basis of Origin :-

Primary Meristem (Promeristem) :-

Derived directly from the meristems of embryo.
They consist ofcells derived from primary meristem.
They add to primary growth of plants.

Secondary meristem :-

These are having cells derived from primary permanent tissue.
They usually add to the diameter of plants.

Classification of Meristematic Tissues on the Basis of Location :-

Apical Meristem :-

It is present at the growing tips of stems and roots.
Cell division in this tissue leads to the elongation of stem & root, thus it is involved in primary growth of the plant.

Intercalary Meristem :-

It is present behind the apex. It helps in longitudinal growth.
It is the part of apical meristem which is left behind during growth period.
These are present at the base of leaf and internode region.
These lead to the increase in the length of leaf (Primary) eg., in grass stem, bamboo stem, mint stem etc.

Lateral Meristem (Cambium) :-

It is also called as secondary meristem.
It occurs along the side of longitudinal axis of the plant.
It gives rise to the vascular tissues.
Causes growth in girth of stem and root.
They are responsible for secondary growth by increasing the girth.

PERMANENT TISSUE :-

The permanent tissues are formed from those meristematic cells which are left behind and have lost their capability to divide.
The division and differentiation of the cells of meristematic tissues give rise to permanent tissues.
They have definite shape, size and thickness. The permanent tissue may be dead or living.
As a result of cell differentiation the meristematic tissues tend to form different type of permanent tissues.
In cell differentiation, developing tissues changes from simple to more complex forms perform various specialized functions.

Types of PERMANENT TISSUE :-

(A) Simple Permanent Tissues (Supporting tissue and protective tissue)
(B) Complex Permanent Tissue
(C) Dermal (Protective) Tissue

(A) Simple Permanent Tissues :-

These are made up of one type of cells which are similar structurally and functionally.

Protective Tissues :- These tissues are primarily protective in function. They consist of :-

Epidermis :-

Epidermis forms one cell thick outermost layer of various body organs of plants such as leaves, flowers, stems and roots.
Epidermis is covered outside by cuticle. Cuticle is a water proof layer of waxy substance called as cutin which is secreted by the epidermal cells and provide protection against provide protection against loss of water and also invasion by microbes.
Each stomata is guarded by a pair of bean-shaped cells called as guard cells. These are the only epidermal cells which possess chloroplasts, the rest being colourless.

Functions of Epidermis :-

The main function of epidermis is to protect the plant from desiccation and infection.
Cuticle of epidermis cuts the rate of transpiration and evaporation of water and prevents wilting.

stomata :-

Cells of epidermis of leaves are not continuous at some places due to the presence of small pores called as stomata.

Function of Stomata :-

It allows gaseous exchange to occur during photosynthesis, respiration and also helps in transpiration.

Cork or Phellem :-

In older roots and stems, tissues at the periphery become cork cells or phellem cells.
Cork is made up to dead cells with thick walls and do not have any intercellular spaces.
The cell wall in cork deposit waxy substance called as suberin.
The cells of cork become impermeable to water and gases due to the deposition of suberin.
The cork cells are without any protoplasm but are filled with resins or tannins.

Functions of Cork :-

Cork is protective in function. Cork cells prevent desiccation, infection and mechanical injury.
Imperviousness, lightness, toughness, compressibility and elasticity make the cork commercially valuable.

Simple Permanent ;-

These are supportive in function and are of three types :-

Parenchyma Tissue
Collenchyma Tissue
Sclerenchyma Tissue

Parenchyma :-

It is the fundamental backing tissue.
Loosely packed thin walled cells, oval or spherical in structure with large space between cells.
Cell wall mainly composed of cellulose & pectin.
Large central vacuole for food & water storage.
Primary function is food storage and packing.

Types of Parenchyma :-

Idioblast :- Some parenchyma involved in storage of excretory substances such as resin, tannin, gum and oils called as idioblast. In typical parenchyma chlorophyll is absent.

Chlorenchyma :- Chloroplast containing parenchyma tissues are called as chlorenchyma which perform photosynthesis e.g., mesophyll of leaves.

Aerenchyma :- In hydrophytic plants aerenchyma (a type of parenchyma containing air spaces) provides buoyancy.

Collenchyma :-

It is the living mechanical tissue.
Elongated cells with thick corners.
Localized cellulose and pectin thickening.
Provides flexibility to plant parts & easy bending ofvarious parts of plant.
Few chloroplasts may be present.
Give mechanical strength elasticity to the growing stems.
They have no or very little intercellular spaces.

Selerenchyma :-

Cells of sclerenchyma are of two types :

Sclereids :-

These are also called grit cells or stone cells.
These are small cells, where lumen is so small due to higher thickening of cell wall, as present in drupe fruit (mango, coconut, walnut) legume seeds (Macrosclereid)

Fibres :-

They are very long, narrow, thick, lignified cells. Lumen is large as compared to sclereids. Generally 1-3 mm long.
In the thick walls of both the fibres and sclereids are present thin areas called as pits.

Uses of Sclerenchyma Fibres :-

These are used in the manufacture of ropes, mats & certain textile fibres.
Jute and coir are obtained from the thick bundle of fibres.

( B ) Complex permanent Tissues :-

It consists of more than one type of cells which work together as a unit.
It helps in transportation of organic materials, water and minerals.
It is also known as conducting or vascular tissue.
Xylem and phloem together from vascular bundles.

Xylem :-

Also known as wood and is a vascular and mechanical tissue. Xylem help in Transportation of water and minerals from soil to plant.

Types of Xylem :-

Xylem consists of four types of cells called as components or elements :-

Tracheids :- They are elongated dead cells (primitive elements) mainly involved in conduction of water and minerals in gymnosperms.

Vessles :- They are advance element (generally found in angiosperms). Vessels are cylindrical tube like structures placed one above the other end to end which form a continuous channel for efficient conduction of water.

Xylem parenchyma :- They are small and thick walled parenchymatous cells designed for storage of starch (food).

Xylem sclerenchyma (fibres) :-

They are non-living fibers with thick walls and narrow cavities which provide mechanical support.
Except xylem parenchyma all other xylem elements are dead.
The annual rings present in the trunk of a tree are xylem rings.
By counting the number of annual rings, we can determine the age of a tree.

Phloem :-

It transport (translocation) food from leaves to other parts of the plant. All phloem cells are living except phloem fibres.

Types of Phloem :-

Phloem consist of four types of components/elements :-

Sieve tubes :-

Sieve tubes are tubular structures made up of elongated, thin walled cells placed end to end.
The end walls of sieve tube cells are perforated by numerous pores, called as sieve plates.
Nucleus of sieve cell degenerates at maturity. However, cytoplasm persists, because of protoplasmic continuation of sieve tube with companion cell through plasmodesmata.

Companion cells :- Companion cells have dense cytoplasm and prominent nuclei. Sieve tubes & companion cells are also called sister cells because they originate from single mother cell.

Phloem fibre/Phloem Sclerenchyma :- They give mechanical support to sieve tubes and are dead.

Phloem parenchyma :- They store food and help in radial conduction of food.

Animal Tissues :-

Different types of animal tissues, such as epithelial tissue, connective tissue, muscular tissue and nervous tissue.

EPITHELIAL TISSUE :-

Cells of epithelium are set very close to each other tightly packed and the tissue rests on a non-cellular basement membrane & consists of single layer of cells.
It covers all the organs and line the cavities of hollow organs like stomach. It is primarily protective in function.

Type of Epithelium :-

Squamous epithelium :- Also called pavement epithelium.

Cells arranged end to end like tiles on a floor.
Cells are polygonal in surface view.
It forms the delicate lining of cavities (mouth, oesophagus, nose, pericardium, alveoli etc.) blood vessels and covering of the tongue and skin.
Epithelial cells are arranged in many layers (stratum) to prevent wear and tear in skin. This pattern is stratified squamous epithelium.

Cuboidal epithelium :-

They are cube like cells that fit closely, cells look like squares in section, but free surfarce appears hexagonal.
It is found in kidney tubules, thyroid vesicles and in glands (salivary glands, sweat glands).
It forms germinal epithelium of gonads (testes and ovaries).
It is involved in absorption, excretion and secretion. It also provides mechanical support.

Colummar epithelium :-

Columnar means ‘pillar-like’ epithelium. It forms lining of stomach.
Small intestine and colon, forming mucous membranes.
Border of micro villi is present at the free surface end of each cell which increases absorption efficiency in small intestine.

Ciliated epithelium :-

Cells may be cuboidal or columnar.
Found in respiratory tract, living of spermduct, oviduct & kidney tubules etc.
On its free surface are present protoplasmic outgrowths called cilia.
It helps in the movement of ova in the fallopian tube.

Glandular epithelium :-

Gland cells secretes substances at the epithelial surface.
Sometimes position of epithelial tissue folds inward and form multicellular gland it is called Glandular epithelial.

Bone :-

Matrix of bone is very hard because of salts such as calcium phosphate,CaCO₃(60-70%) etc. and a protein ossein.
Bone cells (osteoblasts) are embedded in this hard matrix.
Matrix is deposited in the form of concentric layers of lamellae formed around a central canal, the bone cells occupy small spaces between the concentric layers of matrix.

Cartilage :-

This tissue is elastic, less harder as compared to bones.
Elasticity is due to presence of chondrin (protein). Cells are called as chondrocytes which are widely spaced and matrix is reinforced by fibres.
It is found at joint of bones, in the nose, ear, trachea and larynx.
It provides flexibility and great tensile strength.

MUSCULAR TISSUE :-

Movements are brought about in our body with the help of muscular tissue.
They are long fibre-like cells called muscle fibres.
They are capable of contraction or relaxation because they are made up of contractile proteins. (actin and myosin)

Types of MUSCULAR TISSUE :-

Striated muscles :-

These muscles shows alternate light and dark bands hence the name is striped or skeletal muscles.
They are also called as voluntary muscles because these are under the control of one’s will.
Muscle fibers or cells are multinucleated and unbranched.
Each fibre is enclosed by thin membrance which is called as sarcolemma.
Cytoplasm is called as sarcoplasm.
These muscles get tired and need rest.

Cardiac muscle fibres :-

They are involuntary muscles.
Only found in the walls of heart.
They are uninucleated and branched. Branches are united by intercalated disc.
In these muscles rhythmic contraction and relaxation occurs throughout the life and never get tired.

Non-striated muscles or smooth muscle :-

They are involuntary muscles also called as smooth muscles.
These muscle fibres are uninucleated and spindle shaped.
They are not enclosed by membrane but many fibres are joined together in bundles. They constitute internal organs.
Such muscles are found in the walls of stomach, intestine, urinary bladder, bronchi, iris of eye etc.
Peristaltic movements in alimentary canal are brough about by smooth muscles.

NERVOUS TISSUS :-

They are highly specialized tissues due to which the animals are able to perceive and respond to the stimuli.
Their functional unit is called as nerve cell or neuron.
Cell body is cyton covered by plasma membrane.
Short hair like extensions rising from cyton are dendrons which are further subdivided into dendrities.
Axon is long, tail like cylindrical structure with fine branches at the end Axon is covered by a sheath, which is known as myelin sheath.
Nerve ending of one neuron is very closely placed to the dendrons of another neuron to carry impulses from one neuron to another neuron in the form of electrochemical waves. This close proximity is called as synapse.