How Your Kidneys Work

The kidneys are complicated bean-shaped organs located just below your rib cage near the middle of your back. They are your body’s sophisticated trash collectors, maintaining the whole-body homeostatic balance. Your kidneys filter and secrete minerals and metabolites from your blood and excrete them as urine. They process around 200 quarts of blood everyday to screen out extra water and waste products.

Excretion of waste

Your kidneys remove extra water and waste products from your blood as urine. Waste materials come from consumed foods and from the normal breaking down of active muscle. The body utilizes the food you eat for self-repair and energy.

It only takes what it needs and waste products are sent to your blood. The role of the kidneys is to remove these wastes. Otherwise there could be a waste buildup in your blood, which may damage your body.

The filtering process occurs in nephrons, those small units in your kidneys. Each kidney contains around one million nephrons.

In these units, capillaries (tiny blood vessels) intertwine with tubules (small urine-carrying tubes). A complicated chemical change then occurs, as water and waste products leave the blood and get into your urinary system.

Maintaining balance

The kidneys sort out chemicals that can still be used by your body. They measure out such chemicals as potassium, phosphorus, and sodium and discharge them back to your blood.

Through this process, the kidneys regulate the level of these chemicals and substances to your body. Excess levels can harm our body, and it is your kidneys’ biological role to keep the right balance.


Your kidneys are involved in homeostasis. They regulate blood pressure, control blood volume, regulate electrolyte concentrations, and maintain acid-base balance.

The kidneys are important regulators because they can sense plasma concentrations of ions like potassium, sodium, oxygen, hydrogen, and such compounds as creatinine, amino acids, glucose, and bicarbonate.

The kidneys coordinate with other organs, especially those in the endocrine system, to carry out all these homeostatic functions. They communicate through hormones that are secreted into the bloodstream.

Excretion of hormones

In addition to excretion of waste materials, maintaining balance, and homeostasis, your kidneys also excrete three important hormones.

One of these hormones is Vitamin D’s active form, which helps in maintaining calcium for bones and your body’s normal chemical balance.

Another hormone is renin, a blood pressure regulator. The third hormone is erythropoietin (EPO), the one responsible for stimulating your tones to produce red blood cells.