What are the Tasks Performed by Kidneys?

Somehow kidneys do not get the due credit as heart or brain in a human body. But the fact is that this pair of organ has multifaceted system and very important role in a person’s healthy life.

Kidneys filter and return around 200 litres of fluid into the bloodstream every day. Almost 2 litres of the fluid gets converted into urine and the remaining 198 litres are recovered. Hence normally an adult person excretes around 1.5 litres of urine on an average in a single day.

The key functions can be categorized as follow:

1. Elimination of Waste

Human body mechanism has different systems and all the organs in the body have a role to contribute in that system. The kidneys are part of the waste clearance system that helps to remove waste products and balance body's minerals.

Kidneys work in the body just like a filter machine. They perform life-sustaining job of filtering the blood regularly and sending the same to the bloodstream. In this process, some of the fluid gets removed from the body in the form of urine which contains unproductive extra fluid. It is an essential task which prevents accumulation of waste substances in the body to keep it healthy.

Human waste (or human excreta) is referred to extra substances which are not required by our body. It is mainly of three types: urine, sweat and faeces. The kidneys filter out a many water-soluble waste products and toxins into the urine for excretion. Kidneys are linked to bladder with the help of two pipes known as ureters. Urine is collected in the bladder. It remains there between 1 and 8 hours and the urge to urinate starts when the bladder becomes half full. Thereafter our brain gets the signal to release urine.

The following main waste products are excreted through urine

(i) Urea: Urea is made when the body breaks down protein, such as meat. Amino acid is building block for protein. The nitrogen in the amino acid becomes converted to ammonia which is further converted by the liver into urea, which is less toxic than ammonia to the body. The kidneys filters out the urea from the circulation, send it to the bladder along with water and excrete it in the form of urine. Urea is soluble in water. It is how nitrogen is discarded by the body.

(ii) Creatinine: Creatinine is a waste product from the normal breakdown of muscle tissue. As creatinine is produced, it's filtered from the blood through the kidneys and excreted in urine.

(iii) Regulation of nutrients by discarding excess of them from the body: Blood has various substances in it which needs to be kept at the correct level for the body to function properly. We get nutrients from the food we eat and minerals such as sodium (salt), potassium are necessary for our body. However the levels of such nutrients be kept at a certain range. Healthy kidney balances the nutrients range and extra (waste) is excreted through urine. The kidneys also help to adjust the levels of other minerals, such as calcium and phosphate (which are important for bone strength, growth and other functions).

The critical regulation of the body’s salt, potassium and acid content is performed by the kidneys. The kidneys also produce hormones that affect the function of other organs. For example, a hormone produced by the kidneys stimulates red blood cell production. Other hormones produced by the kidneys help regulate blood pressure and control calcium metabolism.

2. Regulation of Body Fluids and Water

In an adult human body weight, 60% is water. Water is an essential element to carry body functions well. For the cells of our body to work properly, it is important that their water content is maintained at the correct level. This means our body must maintain a balance between the water we take in and the water we lose. This is done by the kidneys.

Our bodies take in water from food and drinks. We even get some water when we respire by burning glucose to release energy. We lose water in sweat, faeces, urine and when we breathe out (on a cold day you can see this water as it condenses into vapour).

The kidneys preserve our body's water balance by controlling the water concentration of blood plasma. Healthy kidney does an intelligent job by maintaining correct water level in the body. It excretes extra water which turns in to urine and retains water if body has less fluid in the body due to sweating or less water intake.