Plant and Animal Tissues: Structure and Function

Posted on Oct 29, 2024 in Biology

Plant Tissues

1. Meristematic Tissues

These small, polyhedral cells have thin walls, few vacuoles, and are found in apical and lateral meristems.

Apical Meristems

Responsible for primary growth (lengthening) at the tips of roots and stems.

Lateral Meristems

Responsible for secondary growth (thickening). Two types:

  • Vascular Cambium: Produces vascular tissues.
  • Cork Cambium: Produces cork (suber).

2. Permanent Tissues

Organized into three systems:

Ground System

  • Parenchyma: Living cells.
  • Collenchyma: Living cells providing support in young, growing organs.
  • Sclerenchyma: Often dead cells providing support; two types:
    • Fibers: Elongated cells, raw materials for textiles.
    • Sclereids: Scattered throughout ground tissue.

Vascular System

  • Xylem: Transports water and minerals from roots.
  • Phloem: Transports photosynthetic products.

Dermal System

  • Epidermis: Single layer of flattened cells covered by a cuticle; includes:
    • Stomata: Regulate gas exchange.
    • Trichomes (hairs): Root hairs absorb water and salts; others protect against insects.
  • Periderm: Replaces epidermis in stems and roots with secondary growth; primarily composed of cork.

Animal Tissues

1. Epithelial Tissues

Densely packed cells covering inner and outer surfaces.

Lining Epithelium

  • Simple Epithelium: Single layer of cells.
    • Squamous: Protection and substance exchange.
    • Cuboidal/Columnar: Lining of internal organs; microvilli increase absorption.
  • Stratified Epithelium: Multiple layers of cells; found in skin, mouth, esophagus, and vagina.

Glandular Epithelium

  • Endocrine Glands: Secrete substances directly into the blood.
  • Exocrine Glands: Secrete substances externally.

2. Muscle Tissue

Specialized for contraction.

  • Striated Muscle:
    • Skeletal Muscle: Voluntary contraction.
    • Cardiac Muscle: Involuntary contraction.

3. Nervous Tissue

  • Neuron: Basic functional unit; transmits stimuli.
  • Neuroglia: Support cells.

4. Connective Tissues

Varied tissues with connecting and supporting functions.

  • Loose Connective Tissue: Fills spaces between organs; contains fibrocytes, monocytes, and adipocytes.
  • Dense Connective Tissue: Abundant collagen fibers.
  • Cartilaginous Tissue: Flexible tissue found in skeletons of some fish and embryos; supports joints and airways.
  • Bone Tissue:
    • Compact Bone: Forms the diaphysis of long bones.
    • Spongy Bone: Found in epiphyses of long bones and flat bones.
  • Blood: Composed of plasma and cellular components (red blood cells, platelets).