Overview
This lecture introduces three major types of cell junctions—tight junctions, desmosomes, and gap junctions—explaining their structure, function, and tissue locations.
Tight Junctions
- Tight junctions connect adjacent cells to form a watertight seal.
- They block the passage of water, ions, and molecules between cells.
- Commonly found in the bladder, intestines, and kidneys to prevent leakage.
Desmosomes
- Desmosomes act as spot weld-like connections that anchor cells together.
- They attach to the cytoskeleton for structural support.
- Allow water, ions, and small molecules to pass between cells.
- Found in tissues that experience mechanical stress like skin and intestines.
Gap Junctions
- Gap junctions form tunnel-like connections between cells.
- Permit direct flow of water, ions, and small molecules between adjacent cells.
- Present in tissues requiring electrical coupling, such as cardiac muscle and neurons.
Key Terms & Definitions
- Tight Junction — a watertight connection between adjacent cells that prevents material passage.
- Desmosome — a spot weld-like structure providing strong adhesion and some permeability between cells.
- Gap Junction — a tunnel-like channel linking cells, allowing direct transfer of ions or molecules.
Action Items / Next Steps
- Review locations and functions of tight junctions, desmosomes, and gap junctions.
- Prepare to identify examples of each junction in tissue images.