Tissues and Their Classification

Tissues and Their Classification

• Tissues are groups of similar cells working together to perform specific functions.
• Four primary tissue types in animals: epithelial, connective, muscle, and nervous.

Epithelial Tissue

• Covers body surfaces, lines body cavities, and forms glands.
• Characterized by tightly packed cells with minimal extracellular matrix.
• Functions include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.
• Classified based on cell shape (squamous, cuboidal, columnar) and layers (simple, stratified).
  • Simple squamous: single layer of flattened cells, functions in diffusion and filtration (e.g., alveoli of lungs, lining of blood vessels).
  • Stratified squamous: multiple layers of flattened cells, providing protection against abrasion (e.g., epidermis of skin).
  • Simple cuboidal: single layer of cube-shaped cells, common in glands and kidney tubules (functions in secretion and absorption).
  • Stratified cuboidal: multiple layers of cube-shaped cells, less common than simple cuboidal (functions in secretion and absorption).
  • Simple columnar: single layer of elongated cells, common in digestive tract (functions in secretion and absorption).
  • Stratified columnar: multiple layers of elongated cells, rare and functions in protection and secretion.
• Glandular epithelium forms glands that secrete substances (e.g., hormones, mucus).
  • Endocrine glands secrete products directly into the bloodstream (e.g., hormones).
  • Exocrine glands secrete products into ducts that open onto body surfaces or cavities (e.g., sweat glands, salivary glands).

Connective Tissue

• Supports, connects, and separates different tissues and organs.
• Characterized by a matrix (ground substance and fibers) surrounding cells.
• Functions include binding, support, protection, insulation, transportation (blood).
• Various types of connective tissue:
  • Connective tissue proper: loose and dense connective tissues.
    • Loose connective tissue (areolar, adipose, reticular): supports and connects tissues, stores energy, and provides immune protection.
    • Dense connective tissue (regular, irregular, elastic): provides strength and support (e.g., tendons, ligaments).
  • Cartilage: firm, flexible connective tissue, with specialized cells (chondrocytes) in a matrix containing collagen fibers.
    • Hyaline cartilage: smooth, flexible support and reduces friction (e.g., articular cartilages, trachea).
    • Elastic cartilage: maintains shape while permitting flexibility (e.g., ear).
    • Fibrocartilage: strong and resists compression (e.g., intervertebral discs).
  • Bone: rigid connective tissue with calcium salts and collagen fibers supporting weight, protecting organs, and serving as storage for minerals.
  • Blood: fluid connective tissue that transports substances throughout the body.

Muscle Tissue

• Specialized for contraction and movement.
• Three types: skeletal, smooth, and cardiac muscle.
  • Skeletal muscle: attached to bones, voluntary movement (e.g., biceps, quadriceps).
  • Smooth muscle: in walls of internal organs, involuntary movement (e.g., stomach, intestines).
  • Cardiac muscle: heart, involuntary contractions for blood pumping.

Nervous Tissue

• Specialized for communication and control.
• Composed of neurons (nerve cells) and neuroglia (supporting cells).
• Functions include sensory input, integration, and motor output.
  • Neurons transmit nerve impulses.
  • Neuroglia support and protect neurons.
• Found in the brain, spinal cord, and nerves.

This quiz focuses on the classification and functions of various tissue types, specifically epithelial tissue. Understand the four primary tissue types in animals and delve into the distinct characteristics of simple and stratified epithelial tissues. Perfect for students studying biology or anatomy.