Summary

Tight Junctions, also called zonula occludens or occluding junctions, are cell junctions that function by knitting the membranes of two adjacent cells tightly together, forming a watertight barrier. These junctions are often found in locations exposed to fluids that they must contain - like the linings of the intestines, kidneys and the bladder. On the cellular level, tight junctions are created by coupling the actin Microfilaments of neighboring cells together.

Key Points

• Tight Junctions
  • Also called zonula occludens or occluding junctions
  • Forms a watertight seal
    • Occludin proteins press plasma membranes of adjacent cells tightly against each other
    • Bound by cytoskeletal Microfilaments, made of actin
  • Found in the Intestines, Kidney/Bladder, and the blood brain barrier (BBB)
    • Impermeable barriers contain fluids, prevent leakage, and control absorption
    • Tight junctions fully encircle the apical area of every cell in the epithelial sheet to form a watertight layer