Epithelial Tissues

Epithelial Tissues

1. Basic Structure

   • Apical surface
     • Also called luminal surface. Faces "opening" of some kind.
     • Cilia
     • Microvilli
     • Stereocilia
   • Basal Surface
     • Connects to basement membrane
       • Basal Lamina
         • Type IV collagen
         • Laminin (product of epithelial cells)
       • Reticular Lamina
         • Type III collagen
         • Anchoring fibrils of type VII collagen

2. Intercellular junctions

   • Tight Junctions
     • Interacting proteins form band around top. Controls paracellular diffusion of molecules
     • Connects by Actin microfilaments
   • Adherent junctions (Zona adherens)
     • Connects cytoskeleton w/ actin microfilaments and microtubles
   • Desmosomes
     • Cadherins
       • Desmogleins
       • Desmocollins
   • Hemidesmosomes
     • Anchors skeleton to basal lamina
     • Integrins bound to laminin
       • Laminin in basal lamina!
   • Gap Junctions
     • Connexins
       • Form hexameric complexes called connexons
     • Intercellular communication and direct transfer of small molecules and ions

3. Types

   • Glandular
     • Exocrine
     • Endocrine
   • Covering
     • Simple
       • Squamous
         • Lining of vessels (endothelium) Pericardium Pleural Mesothelial
       • Cuboidal
       • Columnar
     • Stratified
       • Squamous
       • Cuboidal
       • Columnar
       • Pseudostratified
       • Transitional