Which body part provides the fastest route of absorption?

The eyes provide the fastest route of absorption due to the unique anatomical and physiological characteristics of the ocular surface. The conjunctiva and cornea are highly vascularized areas that allow for rapid entry of substances into the systemic circulation. This is because the capillary network present in the conjunctival tissue can quickly absorb chemicals or medications applied to the eye. Additionally, the thin epithelial layer of the cornea facilitates efficient penetration of soluble compounds, bypassing more complex barriers that other routes may encounter.

In contrast, the skin acts as a protective barrier and often requires substances to overcome its stratum corneum for absorption, which can slow the process significantly. The mouth and nasal passages also provide good absorption routes, but they do not match the speed of absorption offered by the eyes, particularly for substances that can evade local metabolism and reach systemic circulation swiftly.