Function of the kidney

The main role of the kidneys is maintaininghomeostasis. They manage fluid levels, electrolyte balance, and other factors that keep the internal environment of the body consistent and comfortable.

These organs carry out a wide range of bodily functions.

Waste excretion

The kidneys removeTrusted Source various waste products and get rid of them in the urine. Some major compounds that the kidneys remove are:

• urea, which results from the breakdown of proteins
• uric acid from the breakdown of nucleic acids
• drugs and their metabolites

Reabsorption of nutrients

The kidneys reabsorbTrusted Source nutrients from the blood using tubules and transport them to where they will best support health. They also reabsorb other products to help maintain homeostasis. Reabsorbed products include:

• glucose
• amino acids
• bicarbonate
• water
• phosphate
• chloride, sodium, magnesium, and potassium ions

Maintaining pH

In humans, the range of acceptable pH levels is 7.35–7.45. At levels below or above this range, the body enters a state of acidemia or alkalemia, respectively. In these states, proteins and enzymes break down and can no longer function. In extreme cases, this can be fatal.

The kidneys and lungs help keep the body’s pH stable. The lungs achieve this by moderating the concentration of carbon dioxide in the blood. The kidneys manage the pH by reabsorbing and producing bicarbonate from urine, which helps neutralize acids. 

The kidneys can retainTrusted Source bicarbonate if the pH is tolerable and release it if acid levels rise. They can produce new bicarbonate by excretingTrusted Source acid.

Osmolality regulation

Osmolality is a measure of the body’s electrolyte-water balance, which is the ratio between fluids and minerals in the body. Dehydration is a primary cause of electrolyte imbalance.

If osmolality rises in the blood plasma, the hypothalamus in the brain responds by passing a message to the pituitary gland. This gland releases antidiuretic hormone (ADH). In response to ADH, the kidney makes several changes, including:

• increasing urine concentration
• increasing water reabsorption
• reopening portions of the collecting duct that water cannot normally enter, allowing water back into the body
• retaining urea in the medulla of the kidney rather than excreting it, as this compound draws in water

Regulating blood pressure

The kidneys regulate blood pressure when necessary, but they are responsible for slower adjustments.

They adjust long-term pressure in the arteries by causing changes in the fluid outside of cells. The medical term for this fluid is extracellular fluid. These fluid changes occur after the release of a vasoconstrictor called angiotensin II. Vasoconstrictors are hormones that cause blood vessels to narrow.

These hormones play a role in increasing the kidneys’ absorption of sodium chloride, or salt. This absorption effectively increases the size of the extracellular fluid compartment and raises blood pressure. Anything that alters blood pressure, including excessive alcohol consumption, smoking,etc…..