ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

What Do The Kidneys Do? A Simple Explanation.

Updated on July 19, 2014

The Kidneys

Humans have two kidneys. Without at least one functioning kidney, the body is unable to survive.

Kidneys are complex, bean-shaped organs located on either side of the spine just below the ribcage, and above the lower back. Each kidney is approximately 2.5" (6cm) wide, 4-6" (11-14cm) long and 1.5" (4cm) thick.

Their main function is to regulate and remove waste from the blood.

"Renal" means "of the kidney" and is found in the names of many of kidney's components.

How Kidneys Work

The outer part of the kidney is fibrous tissue called the renal capsule (9). Inside the capsule are three major structures. The outer part is called the renal cortex, and the deeper part is called the renal medulla. Below that is the renal pelvis. The renal cortex is formed around sections of the renal medulla, creating renal pyramids (1) with renal columns(17) made of renal cortex anchoring the structure.

Blood flows into the kidney from the renal artery (3). This artery divides and branches into smaller arteries called interlobar arteries (2) which go into the renal capsule, and then through the renal columns between the renal pyramids.

Between the renal cortex and the renal medulla are units called nephrons (13). A normal human kidney can contain up to one and half million nephrons. Nephrons are made up of a filtering device called a glomerulus, and tubules to collect filtered blood.

As the blood passes through the nephrons, it is filtered and regulated, and hormones and enzymes secreted by the kidneys are added. The nephrons reabsorb water, glucose, amino acids and salts, controlling the amount of blood, blood pressure, pH balance, and levels of essential chemical compounds.

Waste products are excreted as the fluid we all know as urine, which passes through renal tubules into a collecting duct, and deep into the renal medulla, eventually emptying into the renal pelvis (6), which becomes the ureter (7) leading to the bladder.

This essential function of balancing and regulating the blood is called "homeostasis".

Once the blood has been filtered, it flows into veins which join to flow into the renal vein (4) leaving the kidney.

Every hour the blood is circulated through the kidneys about twelve times. The kidneys generate about 380 pints (180 litres) of liquid called filtrate each day. Almost all of that is reabsorbed, and the average human only excretes approximately 4 pints (2 litres) of urine.

Kidney Structure and Function

Location of the Kidneys

Did You Know ... ?

  • Humans can survive perfectly well with only one kidney.
  • The left kidney is usually slightly larger than the right kidney.
  • The right kidney sits slightly lower than the left kidney.
  • Kidney stones are a very painful build up of solid minerals in the kidneys.
  • A kidney can be transplanted.
  • Dialysis is the method by which a machine helps or replaces the kidneys by cleaning the blood. It is used when there is a severe reduction or failure of the kidneys to carry out their function.

What To Know More?

Janice VanCleave's The Human Body for Every Kid: Easy Activities that Make Learning Science Fun
Janice VanCleave's The Human Body for Every Kid: Easy Activities that Make Learning Science Fun
Finding out how your body works is fun with this interactive book full of super cool experiments. Heaps of activities for kids of all ages.

This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

Show Details
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)