Why do we have 2 Kidneys?


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A small yet great question of a curious mind about its body is why two? Two-eyes, two ears, two-nostrils, two-this, two-that……These all are the attributes of your body those you can notice about yourselves when you stand in front of a mirror or can see in others. But there also lies another pair which is present inside your body which you would be inquisitive to know about. This pair is the pair of your KIDNEYS (I mean of-course apart from your lungs pair). People are very much fascinated by the fact that one can survive with a single kidney only. And hence, the very next query they ask about is “Why do we have two-kidneys then?”

Before hurling to that question directly, you need to know some anatomy of these body parts along with few functions those kidneys perform. Which part basically are kidneys? A commonly perceived phrase about kidneys is “Beans-shaped organs”, which are located in the retroperitoneal space inside the body, on either side below the rib-cage. A retroperitoneal space is a cavity or compartment between your diaphragm and your pelvic area. Kidneys are almost 11 cm in length in adults.

body kidneys


Kidneys, as we all know, filter blood. To be more specific, kidneys remove waste and extra fluid from the body and thus, acting as blood-cleaners. Kidneys also eliminate acids that are produced by some body cells to keep the body healthy. A healthy and perfect functioning kidney purifies nearly half-cup of blood in every-minute to maintain the right quantity of required salts and minerals in the body. Apart from this principle function of theirs, kidneys also produce hormones that help in controlling blood pressure and developing RBC count in your veins.

Every kidney has millions of filtering units called nephrons. These act as a chimney filter; taking the blood and throwing out the undesired toxins and returning the purified blood back in the body.



Well, in general terms, blood flows into your kidneys through renal arteries which then pushes blood to narrower arteries till it reaches nephrons. Nephrons are the ultimate purifying units. The purified blood returns back into your body through renal veins attached to your kidneys and the toxicants get eliminated to the bladder through ureter in form of urine. The bladder acts like a storage site for urine. It stores urine and makes urination controllable.



Being bilateral symmetric our both kidneys perform the same task in the body, both purifies blood. So is that extra-kidney to just fill-up the space created between rib-cage and pelvis? Clearly Not! The other kidney is not any extra organ but it is what that was required by your body. Two are surely better. Your body is a big-machinery that needs to be worked out and intoxicated frequently. Apart from purifying blood your kidneys also have some other functions of blood pressure controlling and helping in RBS formation (as stated above). In a nutshell, they have a huge role in keeping you healthy. For the right-performance of each kidney, we are blessed with a pair rather than just one. Every time you go to pee- you must thank your both the kidneys for that rather than mulling over their number.



The answer is YES! And that is why we are discussing over it here. There are two circumstances-

  1. When a person is born with a single kidney: Shocked? You must be. But, yes there are rare people who are born with a single kidney. This is called “Solitary Kidney”. The reason behind this is:

Birth defects: In some people the second kidney does not even develop while in some cases one of the two-kidneys does not function anyhow. This defect is because of under-development of foetus in mother’s womb. Such people generally do live full and happening life just like other normal people, but, they also have a chance of developing an infection in their kidneys.

There are also the cases when, in early stage of foetus development, both the kidneys developed normally but later they got merged into a single horse-shoe like structured organ.

  1. Surgical removal of kidneys: There are instances when a person needs to surgically get his or her kidney removed in order to get any disease like cancer treated or for donation purposes. In that case, the kidney along with-ureter is removed through surgery.



What if a person donates his kidney? Or what if he needs to surgically get it removed out for any cure? Will he/she survive? If he survived, will he lead a normal healthy life? My answer is encapsulated into a single word-“YES”. And there is a reason behind it. The reason is that the capacity of our kidneys is overabundant. Scientists do believe that one single kidney with its only 75 percent of capacity is enough to help us in sustaining our lives pretty well. Humans have 1.2 million nephrons in their kidneys together, while other animals like mouse have only 12,000 nephrons. No, I am not comparing our bodily needs with that of a mouse, but the contrast needed to be stated. About 120 litres of blood gets purifies each day by a pair of kidneys. Will those 60-litres be left unfiltered if our one kidney does not function well? No, if only one- kidney is present in the body then that single kidney will adjust itself for performing function of a pair. Kidney can increase its performance by increasing the size of each nephron present in it. Due to this that one present-kidney will gain mass equal to two kidneys and that can be nearly one pound.

That is the reason we find kidney-transplant; kidney-donations and other operations related to kidney removal of a person to be often performed operations these days. With advancements in healthcare-technology, medical people are working on artificial kidneys even which are expected to perform the same function as any natural kidney could do.

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