CLASS 7 Biology :Tissues

Tissues

• A group of similar cells that are specialized to perform a specific function is known as tissue.
• Examples: muscle tissue, skin tissue

Organs

• A differentiated structure formed by a group of similar tissues, specialized to perform a specific function, is called an organ.
• Example: Stomach is an organ made up of fat tissue and muscle tissue.

Meristematic Tissue

• Actively dividing cells found at all growing points in a plant, like the tip of roots, stems, and branches.
• Role: divide and produce more cells leading to growth of the plant body.
• Meristematic tissue cells are smaller than cells of permanent tissue.
• Cells have thin cell walls compared to permanent tissues
• Meristematic cells contain large nuclei, permanent cells have small nuclei.
• Meristematic cells lack vacuoles, permanent cells have large vacuoles.
• Meristematic tissue cells actively divide to add new cells, permanent tissue cells do not.

Conducting Tissue

• Also known as vascular tissue.
• Composed of xylem and phloem.

Xylem

• Transports water and minerals absorbed by roots to other plant parts.
• Consists mainly of dead cells.
• Conduction is unidirectional (only upwards from the roots).
• Composed of:
  • Tracheids
  • Vessels
  • Xylem parenchyma
  • Xylem fibres

Phloem

• Transports food manufactured in the leaves to other plant parts.
• Consists mainly of living cells.
• Conduction is bidirectional (both upwards and downwards from the leaves).
• Composed of:
  • Sieve tubes
  • Companion cells
  • Phloem parenchyma
  • Phloem fibres

Types of Animal Tissues

• Epithelial Tissue

  • Covers the surface of the body.
  • Forms the lining of various body cavities and internal organs.
  • Types:
    • Squamous Epithelium: Thin, flattened, polygonal cells. Protective function. Example: Outer layer of skin.
    • Cuboidal Epithelium: Cube-like cells. Concerned with absorption. Example: Inner wall lining of kidney tubules.
    • Columnar Epithelium: Vertically arranged, tall, cylindrical cells. Usually secretory. Example: Inner lining of stomach and intestine.
    • Ciliated Epithelium: Columnar epithelium with cilia. Move substances in its contact. Example: Lining of the windpipe and oviduct.

• Connective Tissue

  • Connects various other tissues and organs.
  • Provides support to different organs.
  • Types:

    • Connective Tissue Proper:

      • Areolar Tissue: Most widely distributed connective tissue. Function: Binds the skin with underlying parts.
      • Adipose Tissue: Stores fat. Function: Stores fat and keeps the body warm.
      • Tendons: Tough, non-elastic structures. Function: Connects muscles to bones.
      • Ligaments: Elastic, strong structures. Function: Connects one bone to another bone.

    • Skeletal Tissue:

      • Cartilage: Solid connective tissue, less hard than bone. Provides flexibility. Example: Nose, external ear.
      • Bone: Hard connective tissue due to calcium phosphate. Functions: Support the body and help in movement of muscles.

    • Fluid Connective Tissue:

      • Blood: Fluid matrix called plasma. Contains red blood cells (RBC), white blood cells (WBC), and platelets. Function: Connects all parts of the body and transports substances.
      • Lymph: Blood-like fluid without red blood cells. Surrounds body cells and protects the body against infections due to the presence of white blood cells.

• Muscular Tissue

  • Forms the muscles of arms, legs, heart, alimentary canal, etc.
  • Responsible for contraction and relaxation, aiding in movements and locomotion.
  • Types:
    • Striated Muscles: Attached to bones. Voluntary muscles (under our control). Example: Arms, legs, face, neck.
    • Unstrained Muscles: Found in intestinal walls, muscles of the iris in the eye, in the wall of the urinary bladder. Involuntary muscles (not under our control).
    • Cardiac Muscles: Found only in the heart walls. Responsible for heart beating.

• Nervous Tissue

  • Made up of elongated cells called neurons.
  • Transmits messages to the brain and back to body parts.
  • Components of a neuron:
    • Cell body (cyton): Contains a prominent nucleus.
    • Dendrons: Short branching structures arising from the cell body.
    • Axon: Long tube-like part with fine terminal nerve endings.

Types of Plant Tissues

• Meristematic tissues:

  • Formative tissues composed of actively dividing cells.
  • Add new cells to the plant body.
  • Help plants grow in length and width.
  • Found in growing regions (tip of the root and tip of the stem).
  • Characteristic features:
    • Small and thin-walled cells.
    • Abundant cytoplasm and large prominent nuclei.
    • Lack of spaces between cells (intercellular spaces) – tightly packed.
    • Active cell division for plant growth.
    • Give rise to permanent tissues.

• Permanent Tissues:

  • Derived from meristematic tissues.
  • Form the bulk of the plant body.
  • Cells no longer small and thin-walled.
  • Cytoplasm is much less, nucleus is small.
  • Cells do not divide and remain the same throughout their life.
  • Classification:

    • Based on Place of Origin:

      • Dermal Tissue: Outermost layer of the plant body. (roots, stem, leaves, flowers, fruits)
        • Functions: Protection, waterproofing, absorption of water and minerals (roots), gas exchange (leaves).
      • Vascular Tissue: Conducts water, minerals, and food to different parts of the plant.
        • Functions: Conduction, mechanical support.
        • Types: Xylem, Phloem.
      • Ground Tissue: (Parenchyma, sclerenchyma, collenchyma) - supporting tissue. Present in roots, stems, leaves, flowers, and fruits.
        • Functions: photosynthesis, food storage, support, and protection.

    • Based on Cell Types:

      • Simple Permanent Tissues:

        • Parenchyma: Thin-walled living cells. Functions: Food storage (potato), photosynthesis.
        • Collenchyma: Living cells with thickenings at the corners. Provides mechanical support.
        • Sclerenchyma: Thick-walled, dead cells. Provides strength to plant parts.

      • Complex Permanent Tissues:

        • Xylem: Conducts water and minerals from roots to plant body (unidirectional).
        • Phloem: Conducts food from leaves to all parts of the plant body.

Tissues

• A group of similar cells that work together to perform a specialized function.
• Examples of tissues: muscle tissue, skin tissue.

Organs

• A differentiated structure formed by groups of similar tissues that work together to perform a specific function.
• Example: stomach, which is made up of muscle tissue and fat tissue.

Meristematic Tissue

• Actively dividing cells located at the growing points of plants like the tip of roots, stems, and branches.
• Responsible for the growth of the plant body.
• Key characteristics:
  • Small cell size
  • Thin cell walls
  • Large and prominent nuclei
  • Lack of vacuoles
• The growth in height and thickness of the stem is due to meristematic tissues.

Green Gram Seeds

• Soaked seeds develop sprouts that grow quickly due to meristematic tissue in the root tip.

Conducting Tissue

• Also known as vascular tissue.
• Responsible for transporting substances within the plant.
• Types:
  • Xylem: Transports water and minerals upward from the roots.
  • Phloem: Transports food manufactured in the leaves throughout the plant.

Collenchyma Tissue

• Composed of elongated cells with thickened corners.
• Provides support to the plant.

Parenchyma Tissue

• Composed of large, thin-walled cells.

Animal Tissue

• Four basic types of animal tissue: epithelial, muscular, nervous, and connective.

Epithelial Tissue

• Found on the surface of the body and lining internal organs and cavities.
• Provides protection, absorption, and secretion.
• Types:
  • Squamous epithelium: Flattened cells, found in the outer layer of skin.
  • Cuboidal epithelium: Cube-like cells, found in the inner lining of kidney tubules.
  • Columnar epithelium: Tall, cylindrical cells, found in the inner lining of the stomach and intestine.
  • Ciliated epithelium: Columnar epithelium with cilia, found in the lining of the windpipe and oviduct.

Muscular Tissue

• Responsible for movement.
• Types:
  • Striated (skeletal) muscles: Voluntary, attached to bones.
  • Unstriated (smooth) muscles: Involuntary, found in the intestinal walls, iris of the eye, and urinary bladder.
  • Cardiac muscles: Found only in the heart, responsible for pumping blood.

Nervous Tissue

• Composed of neurons.
• Responsible for transmitting messages throughout the body.
• Parts of a neuron:
  • Cell body (cyton): Contains the nucleus.
  • Dendrons: Short branching structures that receive messages.
  • Axon: Long, tube-like structure that transmits messages.

Connective Tissue

• Connects various parts of the body, provides support, and stores reserve food material.
• Composed of embedded cells within a matrix.
• Types:
  • Connective tissue proper:
    • Areolar tissue: Most widely distributed, binds the skin to underlying parts.
    • Adipose tissue: Stores fat, provides insulation.
    • Tendons: Tough, non-elastic structures, connect muscles to bones.
    • Ligaments: Elastic structures, connect bones.
  • Skeletal tissue:
    • Cartilage: Less hard than bone, provides flexibility.
    • Bone: Hard due to calcium phosphate, provides support and aids in movement.
  • Fluid connective tissue:
    • Blood: Liquid matrix called plasma, carries blood cells (RBC, WBC, platelets).
    • Lymph: Blood-like fluid without RBC, surrounds body cells, protects against infection.

Plant Tissue

• Two main types: meristematic and permanent.

Meristematic Tissue

• Composed of actively dividing cells.
• Found in growing points of the plant.
• Key characteristics:
  • Small and thin-walled cells
  • Abundant cytoplasm
  • Large, prominent nuclei
  • Lack of intercellular spaces
  • Active division to produce new cells
  • Give rise to permanent tissues.

Permanent Tissues

• Derived from meristematic tissues.
• Form the bulk of the plant body.
• Cells no longer divide and retain their mature structure.
• Key characteristics:
  • Can be thin or thick-walled
  • Reduced cytoplasm
  • Small nucleus
• Types:
  • Dermal tissue: Outermost layer of the plant body, provides protection, waterproof coating, and helps with absorption and gas exchange.
  • Vascular tissue: Responsible for the transport of water, minerals, and food.
    • Xylem: Transports water and minerals from the roots upwards.
    • Phloem: Transports food manufactured in the leaves throughout the plant.
  • Ground tissue: Provides support and performs functions like photosynthesis and food storage.
    • Parenchyma: Thin-walled, living cells, stores food and assists with photosynthesis.
    • Collenchyma: Thickened cell corners, provides support.
    • Sclerenchyma: Thick-walled, dead cells, provides strength and support.
  • Complex permanent tissues:
    • Xylem: Made of vessels and other cells, transports water and minerals upward.
    • Phloem: Made of sieve tubes and other cells, transports food throughout the plant.

Tissues

• A group of similar cells with a shared function forms a tissue.

Meristematic Tissue

• Found in growing points of plants like root tips, stems and branches.
• Cells are small with thin cell walls, large nuclei, and no vacuoles.
• Function: Produce new cells for plant growth.

Permanent Tissue

• Produced from meristematic tissue.
• Cells are larger with thicker cell walls, smaller nuclei and vacuoles.
• Cells do not divide.

Organ

• A structure made up of different tissues that work together for a specific function.
• Examples: Roots, stems, leaves, stomach.

Organ System

• A group of organs that work together to carry out a life function.
• Examples: Digestive system, root system, shoot system.

Organism

• A living being made up of many organ systems working together.

Animal Tissues

• Four main types: Epithelial, muscular, nervous, and connective.

Epithelial Tissue

• Forms a protective outer layer for the body and lines organs.
• Cells are tightly packed with different shapes:
  • Squamous: Flat and protective, like skin cells.
  • Cuboidal: Cube-shaped for absorption, like kidney tubules.
  • Columnar: Tall and cylindrical for secretion, like stomach and intestines.
  • Ciliated: Columnar cells with cilia for movement, like windpipe lining.

Muscular Tissue

• Allows movement through contraction and relaxation.
• Three types:
  • Striated (skeletal): Voluntary movement attached to bones.
  • Unstriated (smooth): Involuntary movement in organs like stomach and blood vessels.
  • Cardiac: Found only in the heart for involuntary pumping.

Nervous Tissue

• Made of neurons (nerve cells) for communication.
• Neuron structure:
  • Cell body (cyton): Contains nucleus.
  • Dendrites: Short branches receiving signals.
  • Axon: Long tube-like structure transmitting signals.

Connective Tissue

• Connects, supports, and protects organs.
• Cells embedded in a matrix (non-living material).
• Types:
  • Connective tissue proper:
    • Areolar: Packaging tissue binding skin to underlying parts.
    • Adipose: Stores fat for insulation and energy.
    • Tendons: Connect muscles to bones, strong and non-elastic.
    • Ligaments: Connect bones to bones, strong and elastic.
  • Skeletal tissue:
    • Cartilage: Flexible, found in nose, ears, and joints.
    • Bone: Hard and strong due to calcium phosphate, provides support and movement.
  • Fluid connective tissue:
    • Blood: Liquid matrix (plasma) with red blood cells, white blood cells, and platelets. Transports nutrients, oxygen, waste, and fights infection.
    • Lymph: Similar to blood but without red blood cells, carries immune cells and waste.

Plant Tissues

• Two main types:
  • Meristematic: Actively dividing cells for growth.
  • Permanent: Non-dividing cells derived from meristematic tissues.

Permanent Tissues (Plant)

• Types based on origin:
  • Dermal: Outermost layer for protection, absorption, and gas exchange.
  • Vascular: Conducting tissues (xylem, phloem) for transporting water, minerals, and food.
  • Ground: Fundamental tissue for support, photosynthesis, and food storage.
• Types based on cell type:
  • Simple:
    • Parenchyma: Thin-walled, living cells for storage and photosynthesis.
    • Collenchyma: Thick-walled at corners for support.
    • Sclerenchyma: Thick-walled, dead cells for strength and support.
  • Complex:
    • Xylem: Transports water and minerals upwards.
    • Phloem: Transports food throughout the plant.

Tissues

• A group of similar cells specialized for a specific function.
• Examples: muscle tissue and skin tissue.

Organ

• A differentiated structure composed of various tissues, working to perform specific functions.
• Example: Stomach

Meristematic Tissue

• Actively dividing cells found at growing points in plants (tip of roots, stems, and branches).
• Role: To divide and produce more cells, leading to plant growth.
• Differences from Permanent Tissues: Smaller size, thinner cell walls, large nuclei, absence of vacuoles, active division.

Green Gram Seeds

• Used to demonstrate meristematic tissue.
• Soaked seeds develop sprouts that grow rapidly due to meristematic tissue at the root tip.

Conducting Tissue (Vascular Tissue)

• Composed of xylem and phloem.
• Responsible for transporting substances within the plant.

Collenchyma Tissue

• Composed of elongated cells with thickened corners.

Parenchyma

• Composed of large, thin-walled cells.

Xylem

• Transportation of water and minerals absorbed by the roots to other parts of the plant.
• Composed mainly of dead cells.
• Unidirectional conduction (upwards from the roots).

Phloem

• Transportation of food manufactured in leaves to other plant parts.
• Consists mainly of living cells.
• Bidirectional conduction (both upwards and downwards from the leaves).

Characteristics of Meristematic Tissue

• Small cells
• Thin cell walls
• Large, conspicuous nuclei
• Almost no vacuoles
• Actively dividing cells

Xylem Components

• Tracheids
• Vessels
• Xylem parenchyma
• Xylem fibers

Phloem Components

• Sieve tubes
• Companion cells
• Phloem parenchyma
• Phloem fibers

Animal Tissues

• Specialized cells organized into four basic types: epithelial, muscular, nervous, and connective.

Epithelial Tissue

• Covers the body's surface and lines internal cavities and organs.
• Functions: protection, secretion, absorption.
• Types:
  • Squamous epithelium: Flattened, polygonal cells (e.g., outer layer of skin).
  • Cuboidal epithelium: Cube-like cells (e.g., lining of kidney tubules).
  • Columnar epithelium: Tall, vertically arranged, cylindrical cells (e.g., lining of stomach and intestine).
  • Ciliated epithelium: Columnar epithelium with cilia (e.g., lining of windpipe and oviduct).

Muscular Tissue

• Responsible for movement through contraction and relaxation.
• Types:
  • Striated muscles (Skeletal muscles): Voluntary muscles attached to bones (e.g. arms, legs, face).
  • Unstrained muscles (Smooth muscles): Involuntary muscles found in internal organs (e.g., intestinal walls, iris of the eye).
  • Cardiac muscles: Involuntary muscles found only in the heart.

Nervous Tissue

• Composed of neurons (nerve cells).
• Functions: transmission of messages to and from the brain.
• Parts of a Neuron:
  • Cell body (cyton): Contains the nucleus.
  • Dendrons: Short, branching structures extending from the cell body.
  • Axon: Long, tube-like part with terminal nerve endings.

Connective Tissue

• Composed of cells embedded in a matrix (non-living medium).
• Types:
  • Connective tissue proper:
    • Areolar tissue: Widely distributed, binds skin to underlying parts (packaging tissue).
    • Adipose tissue: Stores fat, provides insulation (padding tissue).
    • Tendons: Tough, non-elastic structures connecting muscles to bones.
    • Ligaments: Elastic, strong structures connecting bones to other bones.
  • Skeletal tissue:
    • Cartilage: Solid connective tissue, less hard than bone, provides flexibility (e.g., nose, external ear).
    • Bone: Solid, hard connective tissue with calcium phosphate in the matrix, provides support and aids muscle movement.
  • Fluid connective tissue:
    • Blood: Fluid matrix (plasma) with red blood cells (RBCs), white blood cells (WBCs), and platelets.
    • Lymph: Blood-like fluid without RBCs, surrounds body cells and protects against infections.

Plant Tissues

• Two main types: meristematic and permanent.

Meristematic Tissues

• Formative tissues composed of actively dividing cells.
• Role: Increase plant length and width.
• Found at growing points (root tips, stem tips, branches, and lateral sides).
• Characteristics:
  • Small, thin-walled cells.
  • Abundant cytoplasm and large prominent nuclei.
  • Lack of intercellular spaces (cells are tightly packed).
  • Active division.
  • Give rise to permanent tissues.

Permanent Tissues

• Derived from meristematic tissues.
• Form the bulk of the plant body.
• Characteristics:
  • Cells may be larger and have thicker walls.
  • Less cytoplasm.
  • Smaller nuclei.
  • No further division.

Permanent Tissue Classification (Origin)

• Dermal Tissue:
  • Outermost layer of the plant body (epidermis).
  • Functions: Protection, reduction of water evaporation, absorption of water and minerals, gas exchange (stomata).
• Vascular Tissue:
  • Responsible for transporting water, minerals, and food.
  • Composed of xylem and phloem.
  • Functions: Conduction, mechanical support.
• Ground Tissue:
  • Found in various plant parts (roots, stems, leaves, flowers, fruits).
  • Functions: Photosynthesis, food storage, support, protection.
  • Composed of parenchyma, collenchyma, and sclerenchyma.

Permanent Tissue Classification (Cell Type)

• Simple permanent tissues: Composed of one cell type:
  • Parenchyma: Thin-walled, living cells, stores food and participates in photosynthesis.
  • Collenchyma: Living cells with thickened corners, provides support.
  • Sclerenchyma: Thick-walled, dead cells with lignin deposition, provides strength.
• Complex permanent tissues: Composed of more than one cell type:
  • Xylem: Contains vessels (thick-walled, tubular cells) responsible for water and mineral transport.
  • Phloem: Contains sieve tubes (tubular cells with perforated walls) responsible for food transport.