What are the methods of absorption in the human body?
In the case of the human body, there are three main types of absorption; these are pulmonary, percutaneous and gastrointestinal absorption. Pulmonary absorption is the primary route for the absorption and deposition of small airborne particles, vapours, aerosols and gases and is the most efficient way for xenobiotics, foreign substances, in the forms mentioned above to enter the bloodstream or cells via gaseous exchange. The respiratory tract is ideal for its role in gaseous exchange and the absorbance of substances that are airborne or are in a gaseous state because the surface area of the membrane ranges from 30 m2 and 100 m2, meaning that there is a large area for diffusion across the membrane to take place. Behind the epithelial layer there is a substantial network of capillaries, approximately 2000 Km, which increases the total area in which diffusing can occur, increases the time available for diffusion to take place and it increases the rate at which the molecules enter the bloodstream.