Cell Junction

• Cells need to adhere, interact and communicate • PLASMODESMATA (singular: plasmodesma) – Perforations in plant cell walls, lined by plasma membrane – Channels connect cells so cytosol can pass through → Connections unify most of plant

3 main types of cell junctions in animals

  1. Tight junctions

  2. Desmosomes

  3. Gap junctions • All 3 especially common in epithelial (relating to or denoting the thin tissue forming the outer layer of a body’s surface and lining the alimentary canal and other hollow structures) tissue – Lines external and internal surfaces of body

  4. TIGHT JUNCTIONS – Form continuous seals around cells – Prevent leakage of extracellular fluid across layer of epithelial cells

  5. DESMOSOMES – Function like rivets – Fasten cells together into strong sheets

  6. GAP JUNCTIONS – Provide cytoplasmic channels between cells – Similar to plasmodesmata – Ions and small molecules can pass through PLASMA MEMBRANE • 8 nm thick • Controls traffic into and out of the cell • Exhibits selective permeability – Membranes regulate passage of substances across them