module 4

• Epithelial Tissues


  Tissues forming boundaries between external environment and body.
• Basement Membrane


  Supports epithelial cells; composed of basal and reticular lamina.
• Polarity


  Cells exhibit different properties on opposite sides.
• Simple Epithelium


  One cell layer thick; all cells contact basement membrane.
• Pseudostratified Epithelium


  Appears stratified; all cells contact basement membrane.
• Stratified Epithelium


  More than one cell layer thick; only deepest layer contacts basement.
• Squamous Cells


  Wider than tall; allows rapid diffusion.
• Cuboidal Cells


  Equal height and width; spherical nucleus.
• Columnar Cells


  Taller than wide; oval nucleus at base.
• Simple Squamous Epithelium


  Lines blood vessels and alveoli; facilitates diffusion.
• Simple Cuboidal Epithelium


  Lines glands and kidney tubules; secretion and absorption.
• Simple Columnar Epithelium


  Lines intestines; involved in absorption.
• Stratified Squamous Epithelium


  Protects against abrasion; can be keratinized or nonkeratinized.
• Keratinized Stratified Squamous


  Dry; forms epidermis; surface cells nonliving.
• Nonkeratinized Stratified Squamous


  Moist; lines mouth and esophagus; surface cells living.
• Stratified Cuboidal Epithelium


  Lines larger ducts of exocrine glands.
• Stratified Columnar Epithelium


  Lines parts of male reproductive system.
• Transitional Epithelium


  Unique to urinary system; expands with organ distension.
• Avascular


  Lacks blood vessels; nutrients from underlying tissues.
• High Regenerative Capacity


  Epithelial tissues replace sloughed cells rapidly.
• Intercellular Junctions


  Numerous connections for cell attachment and stability.
• Lumen


  Interior space of a tubular structure.
• Exocrine Glands


  Secrete substances through ducts to external surfaces.
• Endocrine Glands


  Secrete hormones directly into the bloodstream.
• Basal Lamina


  Part of basement membrane; secreted by epithelial cells.
• Reticular Lamina


  Part of basement membrane; secreted by fibroblasts.
• Simple Squamous


  Single layer of flat cells, allows diffusion.
• Simple Cuboidal


  Single layer of cube-shaped cells, secretion and absorption.
• Simple Columnar


  Single layer of tall cells, absorption and secretion.
• Pseudostratified Columnar


  Single layer with varying cell heights, often ciliated.
• Stratified Squamous


  Multiple layers of flat cells, protection against abrasion.
• Stratified Cuboidal


  Multiple layers of cube-shaped cells, rare in body.
• Stratified Columnar


  Multiple layers of tall cells, limited distribution.
• Transitional


  Multiple layers, allows stretching in bladder.
• Microvilli


  Finger-like extensions, increase absorption surface area.
• Stereocilia


  Large, nonmotile microvilli, increase surface area.
• Cilia


  Hair-like extensions, propel materials along surfaces.
• Tight Junction


  Barrier junction, prevents material diffusion between cells.
• Adherent Junctions


  Attach cells together, no fusion of membranes.
• Belt Desmosome


  Belt-like junction, encircles cell apex, actin associated.