Animal Tissues Overview

Tissues Overview

• Tissues are groups of similar cells performing specific functions.
• Four fundamental types in the animal body:
  • Epithelial tissue: covers and lines body surfaces.
  • Connective tissue: supports and binds other tissues.
  • Muscular tissue: facilitates body movement.
  • Nervous tissue: transmits stimuli.

Epithelial Tissue (Epithelium)

• Composed of closely packed cells on a basement membrane.
• Lines all body surfaces and cavities, both internal and external.
• Avascular (lacks blood vessels) and capable of rapid regeneration.

Functions of Epithelial Tissue

• Protection: skin acts as a barrier.
• Secretion: salivary glands produce necessary fluids.
• Absorption: occurs in the small intestine.
• Excretion: sweat glands remove waste products.
• Sensation: taste buds detect flavors.
• Reproduction: plays a role in ovaries and testes.

Types of Epithelium

• Covering/Lining Epithelium: Forms sheets covering organs or lining cavities (e.g., skin, stomach lining).
• Glandular Epithelium: Comprises exocrine and endocrine glands.

Classification of Epithelial Tissue

• By Cell Layers:

  • Simple: one cell layer.
  • Stratified: more than two layers.
  • Pseudostratified: one layer with varying cell heights.
  • Transitional: varying layers specifically in certain organs.

• By Cell Shape:

  • Squamous: flat, thin cells.
  • Cuboidal: cube-shaped cells, equal height and width.
  • Columnar: tall, slender cells.

• By Function:

  • Protective: safeguards against injury and infections.
  • Sensory: responsible for receiving stimuli.
  • Germinal: produces sex cells.
  • Glandular: secretes substances for bodily functions.

Simple Epithelial Tissue

• Characterized by a single cell layer, optimized for functions like diffusion and secretion.
• Types:
  • Simple squamous: flat cells, lines air sacs of lungs, blood vessels, and body cavities.
  • Simple cuboidal: cube-shaped cells found in ducts and tubules, such as salivary glands and kidneys.
  • Simple columnar: lines digestive organs, contains goblet cells for mucus secretion.
  • Simple ciliated columnar: cilia aid in moving substances, found in uterine tubes.
  • Pseudostratified ciliated columnar: appears layered but is not; present in respiratory tracts.

Stratified Epithelial Tissue

• Comprises multiple layers, primarily protective and thick.
• Types:
  • Stratified squamous:
    • Keratinized: outer skin layer, waterproof, protects against bacteria.
    • Non-keratinized: moist lining of oral cavity, vagina, and anal canal.
  • Stratified cuboidal: limited in distribution, lines ducts of glands (sweat, salivary, pancreas).