Epithelial Tissue

• Types of Tissue


  • Epithelial
  • Connective
  • Nervous
  • Muscular
• The organs in your body are composed of four basic types of tissues
• Epithelial Tissue


  • Cover body and organ surfaces, line body and cavities and form glands
  • Sheets of closely adhering cells, one or more cells thick
  • Upper surface usually exposed to the environment or an internal space in the body
  • Constitutes most glands
  • Avascular (does not have blood vessels)
  • Usually nourished by underlying connective tissue
  • Have a high rate of mitosis
• Functions of Epithelial Tissue

  • Protect deeper tissues from injury and infection
  • Produce and release chemical secretions
  • Absorb chemicals including nutrients
  • Excrete wastes
  • Selectively filter substances
  • Diffusion
  • Gas exchange
  • Sense stimuli
• Basement Membrane


  • Layer between an epithelium and underlying connective tissue
  • Collagen, reticular proteins, glycoproteins, other protein-carbohydrate complexes
  • Anchors the epithelium to the connective tissue below it
• Basal Surface


  Surface of epithelial cell facing the basement membrane
• Apical Surface


  Surface of epithelial cells that faces away from the basement membrane
• Epithelial Tissue


  • Contains one layer of cells
  • Contains more than one layer of cells
• Simple Epithelia

  Contains one layer of cells
• Stratified Epithelia


  Contains more than one layer of cells
• Simple Epithelia - Naming

  Named by shape of cells
• Stratified Epithelia - Naming

  Named by shape of apical cells
• Simple Epithelia


  • All cells touch basement membrane
• Stratified Epithelia


  • Some cells rest on top of others and do not touch basement membrane
• Types of Simple Epithelia

  • Simple squamous
  • Simple cuboidal
  • Simple columnar
  • Pseudostratified
• Pseudostratified Epithelium


  • Falsely appears stratified, as some cells are taller than others
  • Every cell reaches the basement membrane (but not all cells reach the free surface)
• Goblet Cells


  Wineglass-shaped mucus-secreting cells in simple columnar and pseudostratified epithelia
• Simple Squamous Epithelium

  • Single row of thin cells
  • Permits rapid diffusion or transport of substances
  • Secretes serous fluid
• Locations of Simple Squamous Epithelium

  • Alveoli
  • Glomeruli
  • Endothelium
  • Serosa
• Simple Cuboidal Epithelium

  • Single layer of square or round cells
  • Absorption and secretion, mucus production and movement
• Locations of Simple Cuboidal Epithelium

  • Liver
  • Thyroid
  • Mammary and salivary glands
  • Bronchioles
  • Kidney tubules
• Simple Columnar Epithelium

  • Single row of tall, narrow cells
  • Oval nuclei in basal half cells
  • Brush border of microvilli, ciliated in come organs, may possess goblet cells
• Simple Columnar Epithelium

  Absorption and secretion; secretion of mucus
• Locations of Simple Columnar Epithelium

  • Lining of GI tract
  • Uterus
  • Kidney
• Pseudostratified Epithelium

  • Looks multilayered, but all cells touch basement membrane
  • Nuclei at several layers
  • Has cilia and goblet cells
• Pseudostratified Epithelium

  Secretes and propels mucus
• Locations of Pseudostratified Epithelium

  • Respiratory tract
  • Portions of male urethra
• Stratified Epithelia

  • Range from 2 to 20 or more layers of cells
  • Some cells rest directly on others
  • Only the deepest layer attaches to the basement membrane
• Types of Stratified Epithelia

  • Stratified squamous
  • Stratified cuboidal
  • Stratified columnar (rare)
• Transitional epithelium

  Fourth type of stratified epithelium
• Stratified Epithelia

  • Stratified squamous is most widespread epithelium in the body
  • Deepest layers undergo continuous mitosis
  • Daughter cells push toward the surface and become flatter as they migrate upward
  • Finally die and flake off - exfoliation or desquamation
• Types of stratified squamous epithelia

  • Keratinised
  • Nonkeratinised
• Keratinised Stratified Squamous Epithelia

  • Multiple cell layers
  • Becomes flat and scaly toward surface
  • Resists abrasion
  • Retards water loss through skin
  • Resists penetration by pathogenic organisms
• Locations of keratinised stratified squamous epithelia

  • Epidermis
  • Palms and soles heavily keratinised
• Stratified Cuboidal Epithelium


  • Two or more layers
  • Surface cells square or round
  • Secretes sweat, produces sperm, produces ovarian hormones
• Locations of Stratified Cuboidal Epithelium

  • Sweat gland ducts
  • Ovarian follicles
  • Seminiferous tubules
• Transitional Epithelium


  Multilayered epithelium with surface cells that change from round to flat when stretched
• Transitional Epithelium


  • Allows for filling of urinary tract
• Locations of Transitional Epithelium

  • Ureter
  • Bladder