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What are kidneys? How do they work?

What are the kidneys?

Your kidneys are one of the key vital organs in your body. They are each about the size of a fist, and are located adjacent to your spine, underneath the rib cage. The kidneys are also super chemists. Most of the vital electrolytes and ions in your body are regulated by the kidney, minute to minute, day to day, every single day of your life. These include sodium, potassium, calcium, magnesium, acid levels etc. - an excess or dearth of any of these could make you critically ill and hence the kidneys assume a primary role in regulating them. For example, excess sodium can make one swollen or have very high blood pressure; low levels of sodium can affect one’s brain function or cause low blood pressure.

Most people are born with 2 kidneys. It is estimated that 1 out of every 750 children are born with only one kidney. The kidneys are master purifiers of your blood - the body considers them so important that 25% of the blood pumped by the heart every minute goes to the kidneys. Your kidneys clear close to 50 gallons of your circulating blood off waste products every single day. Removal of waste products that are generated from your diet/metabolism is the key function of the kidneys. No other organ is as hard working or dynamic every single minute of your life!

What is less well known about the kidneys to most people is that they are the organs from which the signal to produce blood from your bone marrow originates. If your kidneys do not function well, one tends to get anemic - and this is the reason why. The signal from the kidneys which is in the form of a hormone (called erythropoietin) is produced in sufficient quantities to stimulate the bone marrow to produce red blood cells.

The kidneys also serve as an organ that produces a few vital hormones - vitamin D which is produced by the skin primarily is activated (or spiked up) in the kidneys so that it can function to maintain bone structure and health in general. When kidneys are diseased, the body lacks vitamin D and makes people prone to fractures and bone loss. The other hormone produced by the kidney is renin, which regulates blood pressure.

Do I need 2 kidneys?

No. We generally do not need all of the kidney function that two kidneys provide. We know that people with one kidney from birth are healthy and we know that we can take a kidney out of a living person and donate it to another person. At some point, if your kidneys are affected by illness, their ability to function may be too little to keep you healthy.

What do my kidneys do?

The kidneys are complicated organs. Most people are aware that the kidneys filter waste to clean the blood but they also perform other functions:

  • balance body fluid

  • balance minerals/electrolytes (such as potassium or magnesium)

  • help regulate acid-base balance

  • produce the active form of vitamin D which is important for strong bones

  • produce hormones important for regulating blood pressure

  • produce a hormone that signals production of red blood cells (which carry oxygen)

  • remove medications from the body


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