The kidneys help control the levels of certain dissolved minerals called electrolytes. They also help filter out waste products called metabolites, that are created by cells using energy. This helps the body maintain stable amounts of compounds such as sodium, potassium and calcium in the blood. It also helps remove potentially toxic compounds that are filtered out of the blood and then concentrated by the kidneys into urine.
How does this happen? The kidneys have nephrons, the loop of Henle, the renal medulla, and the adrenal cortex that help this process take place.
The nephron is the basic structural and functional unit of the kidney. Its function is to regulate the concentration of water and slouble substances like sodium salts by filtering blood, reabsorbing what is needed and excreting the rest as urine. Usually, humans have 800,000 to 1.5 million nephrons in each kidney.
In the kidney, the loop of Henle is the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule. The loop of Henle´s main function is to create a concentration gradient in the medulla of the kidney, near the collecting duct, which is the difference in concentration. This process reabsorbs water and creates a concentrated urine for excretion.
The renal medulla is the innermost part of the kidney. It is split up into a number of sections, known as the renal pyramids. The renal pyramids include the renal artery, the renal tubules, and the renal ureter where blood enters and exits the kidney. The renal medulla contains the structures of the nephrons responsible for maintaining the salt and water balance of the blood. It is hypertonic to the filtrate in the nephron and aids the reabsorption of water.
Situated along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through the production of mineralocorticoids and glucocorticoids, including aldosterone and cortisol respectively. It is also a secondary site of androgen synthesis.
After all this explanation, you may still wonder why is osmosis important in the function of kidneys.Well, Osmosis is a physical and chemical process where any solvent or dissolved chemicals move across a semipermeable membrane seperating two solutions of different concentrations. In other words these solvents or chemicals migrate from an area of high concentration to one of low concentration. For example, if you dissolve something in a liquid, the dissolved compounds which are solutes will spread out until there is an equal concentration of solute everywhere.
Osmosis also provides the primary means by which water is transported into and out of cells. It is also an essential process where nutrients are delivered to the cells. Hence, the movement of water by osmosis is the main reason why it is so important to control the water balance of the body.
To wrap this up, it is osmosis that enables the kidneys to function in the right way. Without osmosis, our kidneys wouldn´t be able to seperate water and other substances from the wastes called urine.