As soon as a user of marijuana smokes a cigarette filled with it or ingest marijuana in any other form, THC (Tetrahydrocannabinol, the primary ingredient of marijuana) and other chemicals make an entry into their body. Both THC and chemicals make their way into the human body through the bloodstream and then move to the brain and thereafter the remaining of the body.
When marijuana smoke is inhaled, THC goes directly to the lungs that lined with tiny air sacs (alveoli) where exchange of gases takes place. These air sacs have a significant surface area, which is about 90 times greater than of the human skin, which makes it easy for marijuana ingredients to enter the human body after the smoke of marijuana is absorbed by the lungs in a matter of just few seconds.
When eaten, marijuana enters the human body to find its place in the stomach where it is absorbed by blood. Thereafter, marijuana is carried by the blood to the liver and the remaining body. It is important to note here that THC is slowly absorbed by the stomach when compared to the lungs and therefore the THC levels are lower and effects last longer when marijuana is eaten.