How do kidneys work?

Our kidneys play a huge role in our body in terms of regulations and cleansing. They also help to produce some of our vital vitamins and balance acid levels in our body.

Their position in each side of your spine and below your ribs and behind your belly. You may not believe it, but the average size of each kidney is around 5-6 inches, that’s the size of a smartphone or fist.

Now to their main job

Kidneys are designed to filter our blood, it passes through our kidneys at least 3 times a day. The waste gets removed, by refining it from water, salt, and minerals modified, if needed. Then the blood gets back to the body clean and ready to maintain us alive. This waste is called urine, and it’s stored in the kidney-pelvis, then it gets drained by a tube called the urethra and heading to the bladder.

Each kidney have 10 million filters called nephrons, and even if your kidneys work on 10% of their potential, you won’t notice any symptoms or change in your body. But if the blood stops supplying them, the kidneys will be severely damaged or die, this is called kidney failure.

They receive blood through the paired renal arteries, blood lives in those veins. In the glomerulus occurs the blood filtration and only 20% of the blood that enters get’s filtered.

What other things kidneys do?

As we all know the kidneys help to filter our blood, they also secreting hormones and helping with our acid-base balance.

How does secretion happen?

Reabsorption is the reverse of secretion, transportation of molecules occurs from the peritubular capillary and through the interstitial fluid, then it goes to the renal tubular cell, and into the ultrafiltrate.

Some of the substances that are secreted are ammonium, hydrogen, potassium, and uric acid. They also bring out functions, that are autonomous of the nephron. They can transform, a precursor of vitamin D to its active form, calcitriol, and synthesize the hormones erythropoietin, calcitriol, and renin.

Erythropoietin is released regarding hypoxia ( due to low level of oxygen at tissue level) straight in the renal circulation. That stimulates erythropoiesis ( this process stimulates the production of the red blood cells) in the bone marrow.  The activated form of vitamin D is Calcitriol, the main job of this form is to absorb the calcium and the renal reabsorption of phosphate. The enzyme called Renin is responsible for the regulation of angiotensin and aldosterone levels.


Extraction is the final process of the ultrafiltration. The whole process of ultrafiltration is like this: ultrafiltrate passes out of the nephron and goes through a tube called collecting duct, and is part of the collecting duct system, and then to the ureters where it is renamed urine. In conclusion, the ultrafiltrate, the collecting duct also takes part in reabsorption.

Blood pressure regulation

The kidneys cannot sense blood, but maintaining proper blood regulation in the long-term is entirely dependent on the kidneys. This occurs entirely through the maintenance of the extracellular fluid chamber, and the size of this chamber depends primarily on the plasma sodium concentration. Retaining is taking the first place for important chemical agents that make up the renin-angiotensin system. If a change occurs in renin adjust the output of this system, in order the hormones angiotensin II and aldosterone. Each of those hormones works on its own mechanism, but both increase the kidney’s absorption of sodium chloride, because of that the extracellular fluid compartment expands and therefore raises blood pressure. Conversely, when renin levels are low, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure.


Dialysis is a treatment when the kidneys are damaged and 85-90% of the function is lost. The main purpose of the dialysis is to filter the waste out of the patient’s body. It removes sodium and metabolic waste from the body also sodium and excess water, thus helps maintain proper blood pressure regulation.  Many patients are expected to live between 5-10  years with dialysis. Some can reach up to 30 years. Dialysis takes place in blood and it goes through a catheter or arteriovenous fistula, or it can be done through the peritoneum.

Land of science advise to take care of your body, and if you feel discomfort anywhere else in your body,  please seek a medical practitioner.

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