Transcellular diffusion refers to molecules moving how?

Transcellular diffusion refers to molecules moving how?

• A. Through intercellular spaces between corneocytes
• B. Directly through the corneocytes
• C. Around hair follicles
• D. Through capillaries in the dermis

Answer: (B)

Transcellular diffusion means the molecule moves directly through the cell itself, crossing both the cell membranes as it traverses the cytoplasm from one side to the other. In the skin’s outermost layer, this involves passing through the corneocytes—the flattened, dead cells that make up the barrier—rather than slipping through the spaces between cells. So the diffusion path is through the interior of the cells and their membranes, not between cells (that would be paracellular diffusion). It also isn’t about moving through hair follicles or into dermal capillaries, which are outside the epidermal barrier. Small, lipophilic molecules tend to diffuse more readily via this transcellular route.

Transcellular diffusion means the molecule moves directly through the cell itself, crossing both the cell membranes as it traverses the cytoplasm from one side to the other. In the skin’s outermost layer, this involves passing through the corneocytes—the flattened, dead cells that make up the barrier—rather than slipping through the spaces between cells. So the diffusion path is through the interior of the cells and their membranes, not between cells (that would be paracellular diffusion). It also isn’t about moving through hair follicles or into dermal capillaries, which are outside the epidermal barrier. Small, lipophilic molecules tend to diffuse more readily via this transcellular route.