Human Respiration and Kinetic Theory


The atmosphere is made up of 78 percent nitrogen and 21% oxygen. For humans the time between inhalation and exhalation is from one second up to four seconds, dependent on the degree of physical exertion, The internal surfaces of a typical pair of human lungs are said to contain “about 480 million alveoli” e.g. tiny air sacs, and “When you breathe in, the alveoli expand to take in oxygen. When you breathe out, the alveoli shrink to expel carbon dioxide.”

It has been calculated that 1 cubic mm of lung tissue contains around 170 alveoli and that the internal surfaces of all of the alveolar sacs in the lungs add up to a total area of between 80 -100 M2.

The average volume of atmosphere inhaled in respiration is around 0.5 litre, in other words in one breathing cycle, of between 1-4 seconds, this volume of atmosphere is inhaled and exhaled.

A cubic millimetre of atmosphere contains 1014 atoms and so on expansion each individual alveolar sac can contain 1014/170 = 612 atoms, of which 1,250,000,000,000 are oxygen atoms.

The alveoli sacs are composed of “just one cell in thickness” and these are covered externally by an equally fine network of blood vessels (capillaries) as shown in the images below. It is observed that between 25% and 30% of the oxygen content of inhaled atmosphere is absorbed through the alveoli into the blood stream, while the remaining oxygen is exhaled, along with all the nitrogen and some carbon dioxide which has been expelled from the blood.


In terms of the currently accepted kinetic atomic theory of gases, 99.9% of the volume of atmospheric gas is empty space, which means that matter, in the form of atoms or molecules, take up 0.1% of the volume of the gas, which, in turn, means that oxygen molecules would take up 0.03% of the volume of the air that we inhale. The average kinetic velocities of these oxygen and nitrogen molecules are in the region of 4-500 metres per second. The molecules of oxygen and nitrogen are traveling at these velocities and colliding with each other and with the internal surfaces of the lungs to maintain an atmospheric level of pressure on these surfaces.

Accordingly, if it is assumed that kinetic atmospheric atoms/molecules in sufficient quantities collide with the inner walls of the alveoli then, as the relative atomic masses of oxygen and nitrogen molecules are very similar at about 16 and 14 respectively and would often be traveling at the same velocities, and bearing in mind that “Any absorption of nitrogen into the blood is very dangerous, a small quantity can cause what deep sea divers call the ‘bends’” :-

How is it possible that that oxygen atoms/molecules are absorbed instantaneously while the nitrogen is instantaneously repulsed?

The third diagram below is an expansion of the second and depicting such a hypothetical process of exchange with ‘kinetic’ gases in the close proximity of lung tissue.

And so:-

How is it possible that these internal alveolar surfaces could be capable of identifying the different characteristics of these gases during the instantaneous kinetic collisions they have with it, so that the 78% of nitrogen molecules engage in perfectly elastic collisions and are repulsed from the surface, while the collisions of 21% of oxygen molecules of similar masses and which are often at identical velocities result in their immediate absorption?

The images below represent the process of human respiratory expansion of alveoli in the lungs, where the automatic muscular expansion of the rib cage combined with that of the diaphragm expands the lung cavities, which draws air into the lungs and results in the coincident expansion of all the alveoli and the concurrent entry of gases into them.

It is obvious that for an oxygen atom to be absorbed into the internal surfaces of the alveoli it is necessary for there to be a reaction, an interaction, between this atom and the surface matter, which could not be instantaneous, however an atom that is in lateral motion over these surfaces and is in close contact with them could interact with this matter.

Obviously the very fine layer of fluid surfactant covering the internal surfaces of the alveoli is designed to interact, to react with the oxygen atoms and to absorb these alone, and to not interact with the nitrogen atoms and any other natural gases that may be present, and to then transfer these oxygen atoms through the single cells of both the alveoli and those of the capillaries into the blood cells.

This process is, ultimately, the result of the progression of human evolution over millions of years.

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