Understanding tissues is one of the most important topics in Central Board of Secondary Education Biology for students of Science. These Tissue Class 9 Science notes are prepared in simple language to help students understand the chapter easily and quickly. In living organisms, a tissue is a group of similar cells that work together to perform a specific function. This chapter explains plant tissues, animal tissues, their structure, functions, and importance in daily life.
These tissues class 9 notes are useful for quick revision before school tests, annual exams, and competitive exam preparation. Students of CBSE Class 9 can learn important concepts like meristematic tissue, permanent tissue, epithelial tissue, connective tissue, muscular tissue, and nervous tissue in an easy way. The notes are based on the latest syllabus of the CBSE board and follows the pattern recommended for academic learning.
Along with theory, these tissue class 9 notes questions and answers also help students practice important exam-based questions. These CBSE Class 9 Notes improve conceptual understanding and make revision faster. Sometimes students feel this chapter is little confusing at first, but with proper explanation and diagrams it becomes much more easier to understand and remember for long time.
Introduction to Tissue
In unicellular organisms (like Amoeba or Paramecium), a single cell carries out all life processes digestion, respiration, excretion, and reproduction. However, as organisms evolved into multicellular forms, the need for specialisation arose.
In multicellular organisms, specific groups of cells are dedicated to specific functions:
- Blood cells transport oxygen, nutrients, and waste.
- Muscle cells generate movement.
- In plants, vascular tissues conduct water and food between different parts.
Definition: A tissue is a group of cells that are similar in structure and origin, organised to perform a specific common function.
Foundational facts:
| Fact | Detail |
|---|---|
| Term coined by | Xavier Bichat (French anatomist) |
| Study of tissues | Histology |
| Plant tissues | Mostly supportive (plants are stationary) |
| Animal tissues | More varied; animals expend more energy due to movement |
| Growth pattern | Localised in plants; uniform throughout in animals |
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Plant Tissue
Plant tissues are broadly classified into two categories:
Plant Tissue
- Meristematic Tissue (actively dividing)
- Permanent Tissue (non-dividing, mature)
Simple Permanent Tissue
- Protective Tissue (Epidermis, Cork)
- Supporting Tissue (Parenchyma, Collenchyma, Sclerenchyma)
- Complex Permanent Tissue (Xylem, Phloem)
Meristematic Tissue
Meristematic tissues are actively dividing tissues found in the growth regions of plants. The word "meristem" comes from the Greek merizein, meaning "to divide."
| Feature | Description |
|---|---|
| Cell wall | Thin, primary, cellulosic |
| Intercellular spaces | Absent (compact arrangement) |
| Vacuoles | Generally absent |
| Cytoplasm | Dense; prominent nuclei |
| Cell organelles | Abundant |
| Metabolic state | Highly active; no stored food |
| Cell cycle | G₁ → S → G₂ → M (actively switched on) |
Classification by Origin
1. Primary Meristem (Promeristem)
- Derived directly from the meristems of the embryo.
- Responsible for primary growth (increase in length) of the plant.
2. Secondary Meristem
- Originates from permanent tissue through a process called dedifferentiation.
- Responsible for secondary growth (increase in girth/diameter).
Process: Permanent Tissue → Dedifferentiation → Secondary Meristem
Classification by Location
| Type | Location | Function |
|---|---|---|
| Apical Meristem | Tips of roots and shoots | Increases length (primary growth) |
| Intercalary Meristem | Base of leaves, internodes | Increases length of internodes/leaves; e.g., grass, bamboo, mint |
| Lateral Meristem | Sides of stems and roots | Increases girth (secondary growth); gives rise to vascular tissue |
Permanent Tissue {#permanent-tissue}
Permanent tissues are formed when meristematic cells differentiatethey lose the ability to divide and acquire a definite shape, size, and function. They may be living or dead.
Differentiation: The process by which meristematic cells develop into specialised permanent tissue, changing from simple to complex forms.
A. Simple Permanent Tissue
These tissues are composed of one type of cell, uniform in structure and function.
Protective Tissue
i. Epidermis
The epidermis forms a single-cell-thick outermost layer covering leaves, stems, roots, and flowers.
| Feature | Detail |
|---|---|
| Cuticle | Waxy waterproof layer of cutin secreted by epidermal cells |
| Cuticle thickness | Very thick in xerophytes (drought-resistant plants) |
| Stomata | Small pores in the epidermis of leaves |
| Guard cells | Bean-shaped pair of cells surrounding each stoma; contain chloroplasts (only epidermal cells with chloroplasts) |
Functions of Epidermis:
- Protects the plant from desiccation and infection
- Cuticle reduces transpiration and prevents wilting
- Stomata allow gaseous exchange during photosynthesis and respiration
- Stomata also regulate transpiration
ii. Cork (Phellem)
In older roots and stems, peripheral cells become cork cells or phellem.
| Feature | Detail |
|---|---|
| Cell state | Dead cells; no protoplasm |
| Cell wall | Thick; impregnated with suberin (waxy, waterproof substance) |
| Intercellular spaces | Absent |
| Contents | Resins or tannins |
Functions of Cork:
- Protective: prevents desiccation, infection, and mechanical injury
- Commercially valuable due to imperviousness, lightness, toughness, compressibility, and elasticity
- Used for insulation and as shock absorbers (linoleum)
- Used in sports goods: cricket balls, table tennis bats, shuttle cocks
A2. Supporting (Ground) Tissue
These provide structural support and are of three types:
i. Parenchyma
The most fundamental and primitive plant tissue.
| Feature | Detail |
|---|---|
| First evolved in | Bryophytes |
| Cell shape | Thin-walled, oval or spherical |
| Cell wall composition | Cellulose and pectin |
| Vacuole | Large central vacuole |
| Primary function | Food and water storage |
Specialised Forms of Parenchyma:
| Variant | Feature | Location/Role |
|---|---|---|
| Chlorenchyma | Contains chloroplasts | Mesophyll of leaves; performs photosynthesis |
| Aerenchyma | Contains large air spaces | Aquatic/hydrophytic plants; provides buoyancy |
| Idioblast | Stores excretory substances | Stores resins, tannins, gums, oils |
ii. Collenchyma
The living mechanical tissue of plants, providing flexible strength.
| Feature | Detail |
|---|---|
| Cell type | Living, elongated |
| Wall thickening | Localised corners — cellulose and pectin deposits |
| Location | Herbaceous dicot stems; thin margins of leaves |
| Chloroplasts | Few may be present |
| Function | Provides mechanical strength, flexibility, and elasticity to growing stems |
iii. Sclerenchyma(Scleras = Hard)
The strengthening tissue of plants; cells are dead at maturity.
| Feature | Detail |
|---|---|
| Cell state | Dead |
| Wall | Extremely thick, lignified (lignin = waterproof) |
| Intercellular spaces | Absent |
| Lumen | Very narrow |
Two types of Sclerenchyma cells:
| Type | Also Called | Description | Example |
|---|---|---|---|
| Sclereids | Stone cells / Grit cells | Small cells with very small lumen due to heavy wall thickening | Drupe fruits (mango, coconut, walnut); legume seeds |
| Fibers | Sclerenchyma fibres | Long (1–3 mm), narrow, thick, lignified; thin areas called pits in walls | Jute, coir, ropes, mats, textile fibres |
B. Complex Permanent Tissue (Vascular Tissue)
Complex tissues consist of more than one type of cell, working together as a functional unit. They form the vascular system of the plant — transporting water, minerals, and food.
Xylem + Phloem together form Vascular Bundles.
i. Xylem (Wood)
Xylem is a vascular and mechanical tissue responsible for conducting water and minerals from roots to leaves. It consists of thick-walled tubular cells.
Four elements of Xylem:
| Element | Nature | Function |
|---|---|---|
| Tracheids | Dead (primitive) | Conduction of water and minerals; mainly in gymnosperms |
| Vessels | Dead (advanced) | Form continuous channels for water conduction; mainly in angiosperms |
| Xylem Parenchyma | Living | Storage of starch (food); only living xylem element |
| Xylem Sclerenchyma | Dead (non-living fibres) | Mechanical support |
Hadrome: Tracheids and vessels are collectively called hadromethe main conducting elements in xylem.
Annual Rings: The xylem rings visible in the cross-section of a tree trunk are annual growth rings. Counting them determines the age of the tree.
ii. Phloem
Phloem transports organic food (sugars) manufactured in leaves to the rest of the plant. Unlike xylem, phloem allows bidirectional movement.
Four elements of Phloem:
| Element | Nature | Function |
|---|---|---|
| Sieve Tubes | Living (no nucleus at maturity) | Main conducting element; food transport (Leptome) |
| Companion Cells | Living (dense cytoplasm, prominent nucleus) | Regulate sieve tube activity; sister cells to sieve tubes |
| Phloem Fibres | Dead | Mechanical support to sieve tubes |
| Phloem Parenchyma | Living | Food storage; radial conduction of food |
Sister Cells: Sieve cells and companion cells originate from the same mother cell. Leptome: The main food-conducting part of phloem, i.e., the sieve tube.
Xylem vs. Phloem — Direction of Movement:
| Tissue | Direction |
|---|---|
| Xylem | Unidirectional (root → leaf) |
| Phloem | Bidirectional (source ↔ sink) |
Animal Tissue
Animal tissues are classified into four main types:
Animal Tissue
- Epithelial Tissue
- Connective Tissue
- Fluid/Vascular (Blood, Lymph)
- Skeletal (Bone, Cartilage)
- Fluid/Vascular (Blood, Lymph)
- Connective Tissue Proper (Areolar, Adipose, White fibrous, Yellow fibrous)
- Muscular Tissue (Striated, Non-striated, Cardiac)
- Nervous Tissue
- Muscular Tissue (Striated, Non-striated, Cardiac)
Epithelial Tissue
Epi = above, thelial = to grow epithelium always grows on top of another tissue.
General Characteristics:
- Cells tightly packed; rests on a non-cellular basement membrane
- Single layer of cells
- Avascular (no blood vessels) and non-nervous
- Covers organs and lines cavities of hollow organs (e.g., stomach)
- Primarily protective in function
Types of Epithelial Tissue:
| Type | Cell Shape | Location | Function |
|---|---|---|---|
| Squamous (Pavement) Epithelium | Flat, polygonal (tile-like) | Mouth, oesophagus, nose, pericardium, alveoli, blood vessels, skin, tongue | Protection; gas exchange |
| Stratified Squamous Epithelium | Multiple layers of flat cells | Skin | Protects against wear and tear |
| Cubical Epithelium | Cube-like; hexagonal free surface | Kidney tubules, thyroid vesicles, salivary and sweat glands, gonads | Absorption, secretion, excretion, mechanical support; forms germinal epithelium |
| Columnar Epithelium | Pillar/column-shaped | Stomach, small intestine, colon (mucous membranes) | Absorption; microvilli increase absorption efficiency |
| Ciliated Epithelium | Cubical or columnar with cilia | Fallopian tubes, respiratory tract | Moves ova through fallopian tubes; moves particles/mucus |
Connective Tissue
Connective tissue cells are widely spaced and embedded in an intercellular matrix. The nature of the matrix determines the tissue's function.
Function: Provides support to different organs and keeps them in place.
Matrix contains: White fibres (collagen — inelastic) and yellow fibres (elastin — elastic).
A. Fluid / Vascular Tissue
i. Blood
Blood is a fluid connective tissue. Its liquid matrix is called plasma.
| Component | Proportion | Composition |
|---|---|---|
| Plasma | ~55% | 90–91% water; 7% proteins (albumin, fibrinogen, globulin); 0.9% inorganic salts |
| Corpuscles | ~45% | RBCs, WBCs, Platelets |
Blood Corpuscles:
| Cell | Also Called | Description | Function |
|---|---|---|---|
| RBCs | Erythrocytes | Contain haemoglobin (red pigment) | Transport oxygen |
| WBCs | Leucocytes ("Soldiers of the body") | Irregular, amoeboid, phagocytic; 5 types: Monocytes, Lymphocytes, Basophils, Neutrophils, Eosinophils | Immunity; engulf bacteria and foreign particles |
| Platelets | Thrombocytes | Spindle-shaped cells | Blood clotting |
Blood transports: nutrients, gases (O₂/CO₂), hormones, excretory products, and heat.
B. Skeletal Tissue
Hard connective tissue that forms the supportive framework of the body.
i. Bone
| Feature | Detail |
|---|---|
| Matrix | Very hard; calcium phosphate (60–70%), CaCO₃, and protein ossein |
| Bone cells | Osteoblasts, embedded in the matrix |
| Structure | Concentric layers of lamellae around a central Haversian canal |
| Marrow cavity | Long bones are hollow; filled with bone marrow |
ii. Cartilage
| Feature | Detail |
|---|---|
| Hardness | Less hard than bone; elastic |
| Elasticity due to | Protein chondrin |
| Cells | Chondroblasts (widely spaced) |
| Locations | Joints, nose, ear, trachea, larynx |
| Function | Flexibility and great tensile strength |
C. Connective Tissue Proper
i. Areolar Tissue
- Most widely distributed connective tissue in the body
- Fills spaces inside organs; found between skin and muscles, around blood vessels, nerves, and in bone marrow
ii. Adipose Tissue
- Oval/round cells (adipocytes) filled with fat globules
- Found in subcutaneous layer (below skin), around heart, brain, and below eyeballs
- Acts as an insulator; prevents heat loss
iii. White Fibrous Connective Tissue
- Little matrix; abundant white collagen fibres (inelastic)
- Bundles form tendons → connect muscle to bone
iv. Yellow Fibrous Connective Tissue
- Abundant yellow elastin fibres in matrix (elastic)
- Forms ligaments → connect bone to bone
Muscular Tissue
Muscular tissue enables movement through contraction and relaxation of long fibre-like cells called muscle fibres.
| Feature | Striated (Voluntary) | Non-Striated (Involuntary/Smooth) | Cardiac |
|---|---|---|---|
| Also called | Skeletal / Voluntary | Smooth / Involuntary | Cardiac muscle |
| Nuclei | Multinucleated | Uninucleated | Uninucleated |
| Shape | Unbranched, cylindrical | Spindle-shaped | Branched |
| Control | Under conscious will | Not under conscious will | Not under conscious will |
| Membrane | Sarcolemma | No individual membrane | Thin sarcolemma |
| Cytoplasm | Sarcoplasm | Sarcoplasm | Sarcoplasm |
| Fatigue | Gets tired; needs rest | Does not tire easily | Never tires; rhythmic |
| Special structure | — | — | Branches joined by intercalated discs |
| Location | Limbs, body wall | Stomach, intestine, urinary bladder, bronchi, iris of eye | Walls of the heart only |
| Function | Body movement | Peristalsis, involuntary organ movements | Rhythmic heartbeat throughout life |
Nervous Tissue
Nervous tissue is the most highly specialised tissue in the body, enabling animals to perceive and respond to stimuli.
Functional Unit: The Neuron (Nerve Cell)
| Part | Description |
|---|---|
| Cyton (Cell Body) | Contains nucleus; covered by plasma membrane |
| Dendron / Dendrites | Short, hair-like extensions from cyton; receive impulses |
| Axon | Long, tail-like cylindrical process; transmits impulses away from cell body; covered by a myelin sheath |
| Synapse | The close proximity between the axon of one neuron and the dendron of another; site of impulse transmission via electrochemical waves |
Types of Nerve Fibres:
- Medullated fibres — covered by myelin sheath; faster conduction
- Non-medullated fibres — no myelin sheath; slower conduction
Functions of Nervous Tissue:
- Controls all body activities
- Coordinates between different body parts
- Makes up the spinal cord and brain
Differences Table
Plant Tissue vs. Animal Tissue
| Feature | Plant Tissue | Animal Tissue |
|---|---|---|
| Mobility | Stationary | Mobile |
| Tissue type | Mostly supportive | Varied (epithelial, connective, muscular, nervous) |
| Growth regions | Localised (meristems) | Uniform throughout |
| Energy consumption | Less | More (due to movement) |
| Dead cells | Common (sclerenchyma, xylem vessels) | Rare |
Xylem vs. Phloem
| Feature | Xylem | Phloem |
|---|---|---|
| Also called | Wood | Bast |
| Conducts | Water and minerals | Food (sugars/organic compounds) |
| Direction | Unidirectional (upward) | Bidirectional |
| Living elements | Xylem parenchyma only | All except phloem sclerenchyma |
| Main conducting element | Tracheids and vessels (Hadrome) | Sieve tubes (Leptome) |
Three Types of Muscle Tissue
| Feature | Striated | Smooth | Cardiac |
|---|---|---|---|
| Striations | Present | Absent | Present (faint) |
| Voluntary control | Yes | No | No |
| Nuclei | Multiple | Single | Single |
| Branching | No | No | Yes |
| Location | Skeletal | Visceral organs | Heart |
Important Facts & Formulas
Terminology Consolidation
| Term | Meaning |
|---|---|
| Histology | Study of microscopic structure of tissues |
| Dedifferentiation | Process by which permanent tissue regains the ability to divide (forms secondary meristem) |
| Hadrome | Tracheids + Vessels (conducting elements of xylem) |
| Leptome | Main food-conducting part of phloem (sieve tubes) |
| Sarcolemma | Membrane surrounding a muscle fibre |
| Sarcoplasm | Cytoplasm of a muscle cell |
| Synapse | Junction between two neurons |
| Haversian Canal | Central canal in bone matrix around which lamellae are deposited |
| Suberin | Waxy substance deposited in cork cell walls |
| Cutin | Waxy substance forming the cuticle on epidermis |
| Lignin | Waterproof substance deposited in sclerenchyma and xylem walls |
| Ossein | Protein present in bone matrix |
| Chondrin | Protein responsible for elasticity of cartilage |
Age of a Tree
Age of tree = Number of annual (xylem) rings counted in the cross-section of its trunk
Composition Formula Reference
| Substance | Composition |
|---|---|
| Blood plasma (55% of blood) | 90–91% water + 7% proteins + 0.9% inorganic salts |
| Blood corpuscles (45% of blood) | RBCs + WBCs + Platelets |
| Bone matrix hardness | 60–70% calcium salts (CaPO₄, CaCO₃) + protein ossein |