What is fluid balance?


Fluid balance refers to the body's ability to manage the amount of water that is retained or excreted. This mechanism is critically managed by the kidneys, which play a pivotal role in either retaining water or causing it to be excreted through urine. The kidneys act like a sophisticated filter system, selectively reabsorbing or excreting different substances, such as glucose, amino acids, urea, uric acid, salt, potassium, and magnesium, based on the body's needs and the concentration of these substances in the blood.

The kidneys respond to hormonal signals, including antidiuretic hormone (vasopressin), which directs them to retain more fluid when necessary. The anatomical feature known as the Loop of Henle in the kidney is particularly significant in regulating this selective retention or release, making fluid balance a dynamic and critical function for maintaining the body's homeostasis 1.

Fluid Balance Mechanism

Andrew explains how the kidney works as a filter to retain or release substances from the body, including sodium, which affects fluid balance. He also shares an interesting fact that urine is actually filtered blood.

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