ICSE 7 Biology Tissues Short

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Table of Contents

    ⚡ Quick Revision: Introduction to Tissues

    A tissue is a group of similar cells that work together to perform a specific function in an organism.

    Term Card

    Histology: The branch of biology that deals with the study of tissues.

    Broad Classification

    • ✔ Plant Tissues: Mostly provide support; many are dead; growth is restricted to specific areas.
    • ✔ Animal Tissues: Mostly living; require more energy for movement; growth is uniform throughout the body.
    [Diagram: Levels of Biological Organization]
    Labeled Figure: Concept of Tissues

    ⚡ Quick Revision: Meristematic Tissue

    Meristematic tissues consist of actively dividing cells that help in the growth of the plant.

    Characteristics of Meristematic Cells

    • ✔ Cells are small, spherical, or polygonal in shape.
    • ✔ Possess thin cellulose walls and very dense cytoplasm.
    • ✔ Lack vacuoles (or have very small ones) because they don't store food.

    Types Based on Location

    Type Position Function
    Apical Tips of stems and roots. Increases length (Primary growth).
    Lateral (Cambium) Beneath the bark/sides. Increases girth/thickness (Secondary growth).
    Intercalary Base of leaves or internodes. Helps in elongation of nodes.
    [Diagram: Location of Meristematic Tissues in Plants]
    Labeled Figure: Growth Regions

    ⚡ Quick Revision: Simple Permanent Tissues

    Concept Note

    Permanent tissues are formed from meristematic cells that have lost the ability to divide and have taken up a specific role. Simple permanent tissues are made of only one type of cell.

    Types of Simple Permanent Tissues

    Type Characteristics Main Function
    Parenchyma Thin-walled, living cells with large intercellular spaces. Storage of food; Photosynthesis (if it contains chlorophyll).
    Collenchyma Living cells thickened at corners with cellulose/pectin. Provides flexibility and mechanical support.
    Sclerenchyma Dead cells with very thick walls due to Lignin. Provides hardness and strength (e.g., husk of coconut).
    💡 Pro-Tip:

    If Parenchyma contains chlorophyll, it is called Chlorenchyma. In aquatic plants, if it has large air cavities to help them float, it is called Aerenchyma.

    [Diagram: Comparison of Simple Permanent Tissues]
    Labeled Figure: Tissue Structures

    ⚡ Quick Revision: Complex Permanent Tissues

    Vascular Bundles

    Complex permanent tissues are made of more than one type of cell that work together as a unit. They are also called Conducting Tissues.

    Xylem vs. Phloem

    Feature Xylem Phloem
    Function Transports water and minerals. Transports prepared food (sugar).
    Direction Unidirectional (upward only). Bidirectional (up and down).
    Composition Tracheids, Vessels, Xylem Fibres, Xylem Parenchyma. Sieve tubes, Companion cells, Phloem Fibres, Phloem Parenchyma.
    Nature Mostly dead cells. Mostly living cells.
    ❌ Don't Confuse:

    Tracheids and Vessels are the main conducting elements of Xylem, while Sieve tubes and Companion cells handle conduction in Phloem.

    [Diagram: Structure and Flow in Vascular Tissues]
    Labeled Figure: Conducting Channels

    ⚡ Quick Revision: Epithelial Tissue

    Animal tissues are classified into four main types: Epithelial, Connective, Muscular, and Nervous. Epithelial tissue forms the protective outer covering and inner linings.

    Characteristics of Epithelial Tissue

    • ✔ Cells are tightly packed with almost no intercellular spaces.
    • ✔ Always rests on a thin, non-cellular basement membrane.
    • ✔ Functions include protection, absorption, secretion, and excretion.

    Common Types

    Type Shape/Feature Location
    Squamous Flat, tile-like cells. Lining of mouth, blood vessels.
    Cuboidal Cube-shaped cells. Kidney tubules, salivary glands.
    Columnar Tall, pillar-like cells. Lining of stomach and intestine.
    Ciliated Have hair-like cilia. Respiratory tract (windpipe).
    [attachment_0](attachment)
    [Diagram: Classification of Epithelial Tissues]
    Labeled Figure: Surface Linings

    ⚡ Quick Revision: Connective Tissue

    Concept Note

    Connective tissues bind, support, and protect different organs of the body. They consist of cells embedded in an intercellular Matrix.

    Major Types of Connective Tissue

    Category Examples Function
    Supportive Bone, Cartilage Provides framework and shape to the body.
    Fluid Blood, Lymph Transport of nutrients, gases, and waste.
    Fibrous Tendon, Ligament Connects muscle to bone (Tendon) or bone to bone (Ligament).
    💡 Exam Focus:

    Bone cells are called Osteocytes and are embedded in a hard matrix of Calcium and Phosphorus. Cartilage has a flexible matrix and is found in the nose tip and external ear.

    Labeled Figure: Connective Tissue Varieties

    ⚡ Quick Revision: Muscular & Nervous Tissues

    Muscular tissue is responsible for movement, while Nervous tissue is responsible for transmitting messages throughout the body.

    Types of Muscular Tissue

    Type Nature Location
    Striated (Skeletal) Voluntary (under our control). Attached to bones (limbs).
    Unstriated (Smooth) Involuntary. Walls of stomach, intestine.
    Cardiac Involuntary & never gets tired. Only in the Heart.

    Nervous Tissue

    Made up of specialized cells called Neurons (Nerve cells). They are the longest cells in the human body.

    • ✔ Cyton (Cell Body): Contains the nucleus.
    • ✔ Dendrites: Short branched fibers that receive messages.
    • ✔ Axon: A long fiber that carries messages away from the cyton.
    Labeled Figure: Anatomy of a Neuron
    ✅ Chapter "Plant and Animal Tissues" Complete. Ready for the next unit?
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