Immortality is it a possibility???

Why do men die? Why do people age? Aging not in the quantitative sense but physical. Forget the philosophical answer for a moment and let the practical/scientific way prevail. Think about it for a while before you move forward reading this blog.
If you have watched the movie "Man from Earth" the answer would have come immediately. The interiors of our bodily system is an epitome of purity. Mind my words!!! Our cells, the mitochondria which ultimately releases the energy needed for our body to sustain, receives the purest form of all the inputs. The lungs, the kidney, the liver, the stomach are the major organs that creates a security net against the foreign impure objects. Whenever the security of this purity is breached there is a problem. However our body has its own way of treating this security breach, and this is what keeps us alive. Over time the amount of impure elements in our body increases. Mostly because the security gates (read kidney, lungs, stomach) stops functioning to their optimum capacity. Thus slowly breaking the web of pristine purity of our body and consequently it starts to age. And once a threshold limit is crossed the man finally dies.
So let me put the bigger picture over here. Our body as a system needs some inputs to sustain ourselves. To help us grow to a certain level. These inputs come mostly in three packages of the good and the evil: the air we breathe, the food we eat and the water we drink. Our bodily systems filter the evil out. Slowly this filtration process weakens, resulting in collection of garbage inside the body, things rotten, worsen and finally dies.
So why immortality is still an impossible concept? The scope of Medical Science till now has mostly been in treating diseases or clearing the garbage out of the body. Vaccination is a small step towards filtration, but still far from it. What is needed is an efficient system that does not allow any foreign body into the body. Can such an external shell of filtration around a human body be created that performs this filtration? I don't find any reason to answer in the negative. However I am not sure whether this right direction towards immortality has actually been identified. Like it is always said "Prevention is better than cure".
Getting back to philosophy: Human beings' every step towards attaining immortality with new drugs have been met with further challenges in the form of new diseases. I am pretty sure when the medical world would turn its attention and make some advance in this filtration mechanism, there would be other challenges faced in gaining immortality. Moreover, just think of filtration on the face value. Smaller the size of the particle difficult is the process. Add to this the fact there has to be a selective filtration, and the filtrates are bacterias, viruses, or molecules of compounds which measures in microns.
Hupps!!!! I am not saying immortality is impossible, but whoever created this universe he made sure that human beings can't get as powerful as him so easily.