Which statement best describes apical and basal surfaces?

• A. Apical faces the free surface; Basal faces the basal lamina.
• B. Apical faces the basal lamina; Basal faces the free surface.
• C. Both apical and basal face the free surface.
• D. Both apical and basal face the basal lamina.

Answer: (A)

The important idea is how epithelial surfaces are oriented. The apical surface is the side exposed to the lumen or outside world—the free surface—while the basal surface sits against the underlying foundation, the basal lamina of the basement membrane. So the apical surface faces the free surface, and the basal surface faces the basal lamina. This arrangement helps cells interact with their environment on the outside and anchor to the connective tissue beneath. The basいいal lamina is produced by epithelial cells and lies just beneath them, helping anchor the tissue; the basal surface is not exposed to the lumen.