Plant and Animal Tissues Overview

Sep 1, 2024

Plant Tissues

Overview

  • Plant tissues are divided into two main groups:
    1. Meristematic tissue
    2. Permanent tissue

Meristematic Tissue

  • Definition: Responsible for growth in plants, located in specific regions.
  • Types:
    1. Epical Meristem:
      • Location: Tips of stem and root.
      • Function: Increases growth in length.
    2. Lateral Meristem:
      • Location: Cork cambium and vascular cambium.
      • Function: Increases girth of plants.
    3. Intercalary Meristem:
      • Location: Found at the base of leaves and at nodes in monocots like grass.

Characteristics of Meristematic Tissue

  • Cells are very active.
  • Dense cytoplasm with prominent nucleus.
  • Thin cell wall.
  • Lack vacuoles (unlike most plant cells).

Permanent Tissue

  • Formation: Formed from the differentiation of meristematic tissue.
  • Differentiation: Unspecialized cells become specialized (like medical students becoming specialists).

Simple Permanent Tissue Types:

  1. Parenchyma:
    • Characteristics: Thin-walled, living cells, loosely packed.
    • Functions:
      • Contains chloroplasts for photosynthesis (chlorenchyma).
      • Stores food (e.g., fruit pulp).
      • Provides buoyancy in aquatic plants.
  2. Collenchyma:
    • Characteristics: Living cells, elongated with irregular thickenings at corners.
    • Functions: Provides flexibility and mechanical support to plants.
  3. Sclerenchyma:
    • Characteristics: Long, narrow, dead cells with thick lignin walls.
    • Functions: Provides mechanical strength, making plant parts hard and stiff.

Epidermis

  • Definition: Protective outer layer of plant bodies, similar to skin in animals.
  • Characteristics:
    • Single-layered, flat, continuous without intercellular spaces.
    • Specialized forms in plants needing extra protection (e.g., thickened in cacti).
  • Functions:
    • Secretes a waxy cuticle on aerial parts to prevent water loss.
    • Contains stomata for gas exchange and transpiration.
    • Root epidermis has root hairs to increase absorptive surface area.

Complex Permanent Tissues

  • Definition: Made of more than one type of cell working together for a common function.
  • Types:
    1. Xylem:
      • Components: Tracheids, vessels, xylem parenchyma, xylem fibers.
      • Function: Transports water and minerals from roots to other plant parts.
    2. Phloem:
      • Components: Sieve cells, sieve tubes, companion cells, phloem fibers, phloem parenchyma.
      • Function: Transports food from leaves to other parts.
  • Vascular Bundles: Xylem and phloem together.

Epithelial Tissue in Animals

  • Definition: Protective covering of organs; lines internal cavities.
  • Features: Continuous sheet of tightly packed cells, minimal intercellular space, separated from underlying tissue by a basement membrane.
  • Functions: Regulates exchange of materials between body and environment (e.g., alveoli in lungs).

Types of Epithelial Tissue:

  1. Simple Squamous Epithelium:
    • Characteristics: Single layer, thin and flat.
    • Locations: Lining of blood vessels, alveoli.
    • Function: Facilitates material exchange.
  2. Stratified Squamous Epithelium:
    • Characteristics: Multiple layers.
    • Location: Skin.
    • Function: Protects against wear and tear.
  3. Cuboidal Epithelium:
    • Location: Kidney tubules, ducts of glands.
    • Functions: Secretion and absorption.
  4. Columnar Epithelium:
    • Location: Lining of stomach and intestines.
    • Functions: Absorption and secretion (with ciliated forms aiding in material movement).

Connective Tissue

  • Definition: Connects different tissues/organs, provides structure.
  • Examples: Blood, bones, cartilage.
  • Common Features: Loosely spaced cells, embedded in intercellular matrix.

Types of Connective Tissue:

  1. Blood:
    • Features: Fluid connective tissue with RBCs, WBCs, and platelets in plasma.
    • Function: Transports nutrients and gases.
  2. Bone:
    • Features: Hard matrix of calcium and phosphorus.
    • Function: Provides shape, support, and protection.
  3. Ligaments:
    • Connects bones; elastic and strong.
  4. Tendons:
    • Connects muscles to bones; fibrous matrix.
  5. Cartilage:
    • Flexible tissue found in joints, nose, ears.
  6. Areolar Tissue:
    • Fills spaces between organs; aids in tissue repair.
  7. Adipose Tissue:
    • Stores fat; insulates body.

Muscular Tissue

  • Definition: Composed of elongated cells (muscle fibers) containing contractile proteins.
  • Functions: Provides shape, support, and movement.

Types of Muscles:

  1. Voluntary Muscles (Skeletal):
    • Under conscious control, striated, multi-nucleated.
    • Examples: Muscles of arms and legs.
  2. Involuntary Muscles (Smooth):
    • Not under conscious control, spindle-shaped, uninucleated.
    • Found in organs like the digestive tract and blood vessels.
  3. Cardiac Muscle:
    • Found in the heart, branched, striated, involuntary.
    • Responsible for heart contractions.

Nervous Tissue

  • Definition: Tissue found in the brain, spinal cord, and nerves.
  • Components: Neurons (nerve cells) and supporting cells.
  • Function: Carries electric impulses; responds to stimuli.

Conclusion

  • This lecture covered various plant and animal tissues, their classifications, features, and functions. Understanding these tissues is crucial for the study of biology and the functioning of living organisms.

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