The human body relies on various organs to maintain its internal balance, a state known as homeostasis. Among these, the kidneys play a central role, constantly working to filter blood and regulate bodily fluids. A common question arises regarding these bean-shaped organs: do both kidneys work at the same time, or do they take turns? Understanding their collective function is key to appreciating their significance in overall health.
The Kidneys’ Teamwork
Both kidneys actively work simultaneously, collaborating in a continuous process to filter the body’s blood. Each kidney contains approximately one million tiny filtering units called nephrons, which are responsible for this intricate work. Blood enters the kidneys through renal arteries, where it is then distributed to these nephrons for filtration. While they perform the same tasks, they process different portions of the blood in parallel, ensuring the entire blood volume is efficiently cleaned.
The kidneys filter a remarkable amount of blood. About half a cup of blood is filtered every minute, totaling around 200 quarts of fluid daily. Most of this filtered fluid is reabsorbed back into the body, with only about two quarts becoming urine.
What Kidneys Do
The kidneys perform a variety of functions beyond simply filtering waste, all important for maintaining health. They are primarily responsible for removing waste products and toxins from the blood, such as urea and creatinine, which are byproducts of metabolism.
Kidneys also regulate fluid and electrolyte balance. They control the levels of important minerals like sodium, potassium, calcium, and phosphate, ensuring these electrolytes remain within a healthy range for proper nerve and muscle function. Kidneys also control blood pressure through mechanisms like the renin-angiotensin-aldosterone system. They influence blood pressure by regulating sodium and water balance, which directly affects blood volume.
Beyond filtration and regulation, kidneys produce several hormones. They secrete erythropoietin, which stimulates the bone marrow to produce red blood cells, and renin, an enzyme involved in blood pressure regulation. Kidneys also activate vitamin D, transforming it into a form that helps the body absorb calcium for bone health. Finally, they maintain the body’s acid-base balance by reabsorbing bicarbonate and excreting hydrogen ions, thereby keeping blood pH within a narrow, healthy range.
Living with One Kidney
While most individuals are born with two kidneys, it is possible to live a healthy and normal life with only one. This is because the remaining kidney can compensate for the absence of the other. This compensation involves a process called compensatory hypertrophy, where the single kidney increases in size. Along with enlargement, the kidney also undergoes hyperfiltration, meaning its individual filtering units, the glomeruli, increase their filtration rate.
The remaining kidney can take on a significant portion of the workload, sometimes achieving up to 70-85% of the function normally performed by two kidneys. This adaptive capacity helps maintain overall kidney function within a healthy range. Individuals living with one kidney should prioritize a healthy lifestyle, including a balanced diet and regular exercise, and may need to avoid high-impact sports to prevent injury. Regular medical check-ups are also important to monitor kidney function, blood pressure, and protein levels in the urine, ensuring the long-term health of the single kidney.