In details

Occlusion Zone

Another type of cell junction present in many epithelia is the occlusion zone, a kind of adhesive belt located near the free edge of epithelial cells.

The occlusion zone keeps neighboring cells so close that it prevents molecules from passing between them. Thus, substances that may be present in a cavity lined with epithelial tissue cannot penetrate the body unless directly passing through the cells.

Basal lamina and hemidesmosomes

Under an epithelial tissue there is always a kind of carpet of protein molecules to which cells attach: the basal lamina. Epithelial cell bases are adhered to the basal lamina through special cell structures called hemidesmosomes. They resemble desmosomes, but have a different structure and function, connecting epithelial cell bases to the basal lamina, rather than connecting the membranes of neighboring cells, as desmosomes do.