Final answer:
The order of cell junctions from basal to apical surfaces in epithelial cells is tight junctions, adherens junctions, desmosomes, and hemidesomes.
Step-by-step explanation:
From the basal surface to the apical surface of an epithelial cell, the order of cell junctions observed in the junctional complex is typically as follows:
- Tight junctions: These are at the apical region of the cell and create a barrier that restricts the flow of substances between the cells.
- Adherens junctions: Positioned just below the tight junctions, they encircle the cell and provide strong mechanical attachments between adjacent cells through cadherin proteins and actin filaments.
- Desmosomes: Located below adherens junctions, these patch-like structures provide strong adhesion by linking to intermediate filaments inside the cell.
- Hemidesmosomes: Found at the basal surface, these half-desmosome structures attach epithelial cells to the basal lamina via integrins.
This order of junctions enables epithelial tissues to function as selective barriers and maintain structural integrity while being flexible.