Introduction to Human Body Tissues

Jul 23, 2024

Types of Human Body Tissues

Overview

  • Tissues: Collections of cells similar in structure & function.
  • Importance in multicellular organisms for specialization & complexity.
  • 4 Types to know: Epithelial, Connective, Nervous, Muscle.

Epithelial Tissue

  • Function: Covers external & internal surfaces, forming boundaries.
  • Locations: Skin, body cavities (digestive, respiratory), blood vessels, organs.
  • Types:
    • Covering & Lining Epithelium
    • Glandular Epithelium
  • Key Features:
    • Polarity: Apical surface (exposed/outside), Basal surface (attached/inside).
    • Apical surface: Often lined with microvilli or cilia for secretion/absorption or propulsion.
    • Basal Lamina: Glycoproteins & collagen, scaffolding for the Basement Membrane (Basal + Reticular Lamina).
    • Cell Arrangement: Sheets, connected by desmosomes, tight junctions, gap junctions.
    • Avascular: No blood vessels, but innervated (supplied with nerves).
    • Regenerate quickly: Due to high friction & potential for injury.
  • Functions: Protection, absorption, filtration, excretion, secretion, sensory reception.

Classification of Epithelial Cells

  • Layering:
    • Simple Epithelia: Single cell layer.
    • Stratified Epithelia: Multiple cell layers.
  • Shape:
    • Squamous: Flat, scale-like.
    • Cuboidal: Boxy, medium height.
    • Columnar: Tall, column-like.
  • Examples:
    • Simple Squamous Epithelium: Ideal for diffusion (e.g., endothelium, mesothelium).
    • Simple Cuboidal Epithelium: Secretion & absorption.
    • Simple Columnar Epithelium: Secretion & absorption, particularly in digestion.
    • Pseudostratified Columnar Epithelium: Looks stratified due to staggered nuclei/cell heights.
    • Stratified Squamous Epithelium: Protection, common in skin. Surface cells are squamous, deeper cells can be cuboidal/columnar.
    • Stratified Cuboidal/Columnar Epithelium: Rare, found in some glands.
    • Transitional Epithelium: Can stretch, found in urinary system.

Glandular Epithelium

  • Glands: Produce & secrete substances.
  • Types:
    • Exocrine Glands: Secrete substances via ducts onto surface.
    • Endocrine Glands: Secrete substances directly into blood.

Next: Connective Tissue