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Learn How the Kidneys Work

Last updated date: 23rd Feb 2024
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What are Kidneys?

Excretion is an important life process for the functioning of the human body. Kidneys form a key part of the human body’s excretory process. They are bean-shaped organs about the size of fists (10-12 cm) with a width of around 5-7 cm. They weigh about 115-175 grams. Kidneys are essential organs for the filtration of blood in our body and for the process of excretion. They filter out unwanted materials from the body in the form of urine and return the clean blood for circulation. 

Where are Kidneys Located in the Body?

The kidneys are located below the diaphragm on either side of the spine. The part of the body above the diaphragm is called the chest and the lower one is called the abdomen. Kidneys are located in the abdomen area and are protected by the rib cage.

Location of the kidneys

Location of the kidneys

Interesting Facts About Kidneys

Apart from balancing the amount of fluid in our body, and getting rid of waste materials from the blood, there are a lot of other facts that you should know about kidneys.

  1. Although most human beings are born with two kidneys, our bodies can sustain even with the help of one.

  2. Each kidney has approximately 1 to 2 million nephrons.

  3. The position of the kidneys in our body is not symmetrical, our right kidney is located a little lower than the left one.

  4. Our right kidney also tends to be a little smaller than our left one.

  5. Kidneys also help to maintain our body’s blood pressure by responding to a hormone called aldosterone which is produced in the adrenal glands.

  6. Kidneys also produce Vitamin D which promotes healthy bones.

  7. Kidneys also control the production of red blood cells.

  8. The two kidneys together filter around half-cup of blood every minute, approximately 180 L of blood per day.

How do Kidneys Clean the Blood?

Each kidney consists of around a million nephrons. The nephrons are called the filtering unit because they consist of a filter, called the glomerulus, and a tubule.

A Nephron

A Nephron

The glomerulus filters the blood and the tubule returns the essential substances to our blood and removes the waste products. The blood enters our kidneys through the renal artery. It then reaches the nephron through smaller and smaller blood vessels.

In the nephron, it is filtered with the help of the glomerulus and the tubule. The filtered blood is then sent from the kidneys through the renal vein. The urine produced by the kidneys after the filtration process is stored in the Bladder through the Ureter. From the Bladder, it is excreted out of the body via the Urethra.

Learning by Doing

Q1) Which of the following organs stores urine after filtration of blood?

  1. Ureter

  2. Urethra

  3. Renal artery

  4. Bladder

Ans: d. Bladder

Q2) Which of the following is the filtering unit of kidneys?

  1. Tubule

  2. Renal vein

  3. Nephron

  4. Glomerulus

Ans: c. Nephron

Solved Questions

1. Explain the functioning of nephrons.

Ans: Nephrons filter out the blood in a two-level process. Each nephron has a glomerulus and a tubule. The blood after entering the nephron goes to Glomerulus – a tangle of tiny blood vessels. Glomerulus has thin walls which allow the waste materials, water, and smaller molecules to pass through the tubule. Essential minerals such as proteins stay in the blood vessel. As the blood moves through the tubule, other essential minerals and water are reabsorbed by a blood vessel that runs along the tubule. The remaining waste and fluid make urine.

2. Draw a labelled diagram of the urinary tract.

Urinary Tract

Urinary Tract


Kidneys are essential for the survival of an individual. They provide a variety of features for the body to function healthily. They are most importantly responsible for the cleansing of our blood. We have also learnt that human beings can survive with just one kidney. We have discussed other functions of the kidney such as the production of vitamin D, maintenance of blood pressure, etc.

FAQs on Learn How the Kidneys Work

1. What is the role of the ureter?

The ureter is responsible for carrying urine produced during the filtration of blood to the Bladder.

2. How many nephrons are there in each kidney?

There are approximately 1 to 2 million nephrons in each kidney.

3. What are the roles of the renal veins and renal arteries?

Renal veins carry the filtered blood from the kidneys to the heart for circulation to the rest of the body.

Renal arteries carry the unfiltered blood from the heart to the kidneys for filtration.