The Diaphragm vs. The Kidneys
Five Towns College Adjunct Professor and Author, Rasheem J. Northington, breaks down the relationship between these critical body functions in a special feature for the FTC Record.

The function of the thoracic diaphragm has the potential and capability of increasing the efficiency of the kidneys by way of increasing their efficiency of filtration.
The kidneys are the organs that are responsible for removing wastes that come from natural metabolic reactions in the body, as well as toxins, excess fluid, excess ions including acids and other substances that serve no useful purpose in the body. The excess accumulation of wastes in any system decreases the efficiency of the system and with living systems such as humans, the accumulation of wastes in the body can also negatively impact health. It is important to have healthy working kidneys in order to promote good health in the body, as the kidneys would promote good health by keeping the level of wastes in the blood stream low enough so that they do no appreciable harm to health. Basically, the kidneys act as a filter for the blood.
Simply put, in the kidneys there is a filtration membrane. This filtration membrane in the kidneys is called a glomerulus, there may be a million of these. This glomerulus is a ball of capillaries and capillaries are blood vessels that are permeable to blood plasma which is the water portion of the blood containing dissolved solutes. Capillaries are however impermeable to plasma proteins. Now these capillaries in the kidneys are responsible for the filtration of the blood and they are positively influenced by a hormone called atrial natriuretic peptide or (ANP).
Breaking the words down, “atrial” is referring to the right atrium of the heart. The right atrium of the heart, which is one of the four chambers of the heart, is the chamber of the heart that receives the venous blood return from the vena cava. The word “natriuretic” broken down; the “natri” part of the word means salt and “uretic” relates to excretion and “peptide” is a small protein. So, the atrial natriuretic peptide is a small protein released from the heart cells of the right atrium that produces a positive effect on the kidneys and relates to salt excretion.
Now it is this peptide (ANP) that produces a positive effect on the kidneys. The positive effect that this peptide has on the kidneys function is that it stimulates the kidneys to increase their efficiency. More specifically, the peptide stimulates the kidneys to increase their efficiency by the effect that it has on the capillaries in the kidneys that are responsible for filtration. ANP increases the efficiency of the kidneys by maximizing the surface area of these capillaries that are available for filtration. This maximizes the filtration and the cleansing of the blood by these “glomerular” capillaries, resulting in an increase of the filtration rate. The filtration process cannot be any more efficient than the availability of its filtration membrane meaning, its capillary availability. In consequence more water is filtered along with a greater amount of solutes that would have a greater chance being released or excreted rather than remaining in the blood stream.