Kidney: Structure, Function and Related Diseases

The kidneys are vital organs responsible for several essential functions in the body. Let’s explore their structure, functions, and some related diseases

Kidney Structure, Function and Related Diseases

Structure of the Kidneys

  • The human body typically contains two kidneys, located on either side of the spine, just below the ribcage.
  • Each kidney is about the size of a fist and has a bean-shaped structure.
  • The outer region of the kidney is called the renal cortex, and the inner region is the renal medulla.
  • The renal pelvis is a funnel-shaped cavity that collects urine and leads to the ureter, which transports urine to the bladder.
  • Each kidney contains millions of functional units called nephrons, which filter blood and form urine.

Functions of the Kidneys

  1. Filtration: The primary function of the kidneys is to filter waste products, toxins, and excess substances from the blood through the nephrons. This process creates a liquid waste product called urine.
  2. Fluid and Electrolyte Balance: The kidneys play a crucial role in maintaining the body’s fluid and electrolyte balance. They regulate the levels of sodium, potassium, calcium, and other ions in the blood.
  3. Acid-Base Balance: The kidneys help regulate the body’s pH by excreting hydrogen ions and reabsorbing bicarbonate ions, ensuring the blood remains within a narrow pH range.
  4. Blood Pressure Regulation: The renin-angiotensin-aldosterone system, controlled by the kidneys, helps regulate blood pressure. The kidneys produce renin, an enzyme that triggers a series of reactions to control blood pressure and fluid balance.
  5. Red Blood Cell Production: The kidneys produce erythropoietin, a hormone that stimulates the bone marrow to produce red blood cells, thus helping maintain adequate oxygen-carrying capacity in the blood.

How does blood flow through my kidneys?

Blood is delivered to the kidney via the renal artery, which gradually branches into smaller vessels until it reaches the nephron. Inside the nephron, blood undergoes filtration in the glomeruli, where waste products and fluids are separated. From there, blood exits the kidney through the renal vein.

Throughout the day, your blood circulates through the kidneys several times, with about 150 quarts filtered daily. The glomeruli filter out water and other substances, but most of these are absorbed back into the bloodstream by the tubules. 

As a result, only 1 to 2 quarts of this filtered fluid eventually becomes urine. In children, the amount of urine produced is less than in adults, and it can vary depending on their age.

Related diseases and conditions

  1. Chronic Kidney Disease (CKD): CKD is a progressive condition in which the kidneys gradually lose their function over time. It can result from various factors, such as diabetes, high blood pressure, glomerulonephritis, or polycystic kidney disease.
  2. Acute Kidney Injury (AKI): AKI is a sudden and severe decrease in kidney function, often caused by conditions like dehydration, severe infection, or kidney damage from medications or toxins.
  3. Kidney Stones: Kidney stones are hard mineral and salt deposits that form in the kidneys. They can cause severe pain and may require medical intervention for removal.
  4. Urinary Tract Infections (UTIs): UTIs are infections that can occur in any part of the urinary system, including the kidneys. They are typically caused by bacteria and can lead to kidney infections if left untreated.
  5. Polycystic Kidney Disease (PKD): PKD is a genetic disorder characterized by the growth of fluid-filled cysts in the kidneys, leading to kidney enlargement and potentially affecting kidney function.

It is important to maintain good kidney health through a balanced diet, regular exercise, and staying hydrated. If you experience any symptoms or concerns related to your kidneys, it is essential to seek medical advice from a healthcare professional. Early detection and proper management of kidney-related issues can significantly improve outcomes and quality of life.


The kidneys are responsible for filtering waste products, excess fluids and toxins from the blood to make urine. They also help regulate the body’s fluid and electrolyte balance, control blood pressure, and produce hormones such as erythropoietin, which stimulates red blood cell production.

  • Stay hydrated by drinking plenty of water daily.
  • Follow a balanced diet that is low in sodium, processed foods and added sugars.
  • Control blood pressure and blood sugar levels if you have high blood pressure or diabetes.
  • Avoid overuse of over-the-counter pain medications such as NSAIDs.
  • Exercise regularly and avoid smoking.

While some kidney diseases may have a genetic or unavoidable component, many cases can be prevented or their progression slowed by adopting a healthy lifestyle. Regular medical checkups, maintaining a healthy diet, being physically active, and managing underlying health conditions such as diabetes and high blood pressure can reduce the risk of kidney diseases.

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