Pharmaceutics Xenobiotics Across Bio Membrane Practice Test

The main concept here is that skin thickness governs how readily substances penetrate. Permeability through the skin generally increases as the barrier becomes thinner, so areas with a thinner stratum corneum allow more diffusion than thick, calloused regions. The scrotum has very thin skin and a relatively permeable barrier, while the heel has thick, tough skin that presents a larger barrier to diffusion. Seeing higher penetration in the scrotum than in the heel directly supports the idea that reduced thickness enhances penetration. The other options suggest higher penetration in areas with thicker skin or reverse the comparison, which would not align with how thickness influences permeability.