How does the kidney regulate salt and water balance?
The kidneys maintain our body's water balance by controlling the water concentration of blood plasma. The kidneys also control salt levels and the excretion of urea. Water that is not put back into the blood is excreted in our urine.
The kidneys produce urine which is made up of waste products, excess mineral ions and excess water from the body. The main job of your kidneys is to regulate the amount of water in the body and balance the concentration of mineral ions in the blood.
- Sodium levels are regulated by the kidney and adrenal gland. The adrenal gland produces a hormone called aldosterone that tells the kidneys how much sodium to retain. When either sodium or potassium becomes unbalanced, the kidney may expend the other electrolyte to maintain a balance.
- Direct control of water excretion in the kidneys is exercised by vasopressin, or anti-diuretic hormone (ADH), a peptide hormone secreted by the hypothalamus. ADH causes the insertion of water channels into the membranes of cells lining the collecting ducts, allowing water reabsorption to occur.
- The kidneys secrete a variety of hormones, including erythropoietin, calcitriol, and renin. Erythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation. It stimulates erythropoiesis (production of red blood cells) in the bone marrow.
In renal failure, acute or chronic, one most commonly sees patients who have a tendency to develop hypervolemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and bicarbonate deficiency (metabolic acidosis). Sodium is generally retained, but may appear normal, or hyponatremic, because of dilution from fluid retention.
- This means, in the days between your dialysis treatments, your body holds on to excess fluid and waste your kidneys cannot remove. Going over your recommended fluid allowance can cause swelling and increase your blood pressure, which makes your heart work harder.
- Acute kidney injury (AKI), previously called acute renal failure (ARF), is an abrupt loss of kidney function that develops within 7 days. Its causes are numerous.
- Causes of acute kidney injury. Most cases of AKI are caused by reduced blood flow to the kidneys, usually in someone who is already unwell with another health condition. This reduced blood flow could be caused by: low blood volume after bleeding, excessive vomiting or diarrhoea, or as seen with severe dehydration.
The cardiovascular system works in conjunction with other body systems (nervous and endocrine) to balance the body's fluid levels. Fluid balance is essential in order to ensure sufficient and efficient movement of electrolytes, nutrients and gases through the body's cells.
- Canned tuna, canned salmon, soup, beans, pickles, olives and whole-grain bread are higher-sodium foods that are actually good for you. Since most of these foods are seasoned with table salt (a.k.a. sodium-chloride) you'll find both electrolytes. Milk, cheese and yogurt are packed with bone-building calcium.
- (1) ADH (antidiuretic hormone) from the posterior pituitary acts on the kidney to promote water reabsorption, thus preventing its loss in the urine. (2) Aldosterone from the adrenal gland acts on the kidney to promote sodium reabsorption, thus preventing its loss in the urine.
- Here are some of the most abundant electrolytes and why our body requires them.
- Calcium. Calcium is the most abundant electrolyte in the human body.
- Potassium. If you watch sports, you'd notice that athletes always seem to have a banana with them.
Updated: 21st November 2019