Plasma osmolality is the osmolality of human blood. Normal osmolality in plasma is about 280 - 303 milli-osmoles per kilogram. This is contributed to mainly by sodium, chloride, potassium, urea, and glucose, and additionally by other ions and substances in the blood. When substances are dissolved, the number of distinct particles in solution is measured as Osmolality. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... The chloride ion is formed when the element chlorine picks up one electron to form an anion (negatively-charged ion) Cl−. The salts of hydrochloric acid HCl contain chloride ions and are also called chlorides. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula CON2H4 or (NH2)2CO. Urea is also known as carbamide, especially in the recommended International Non-proprietary Names (rINN) in use in Europe. ... Glucose (Glc), a monosaccharide, is one of the most important carbohydrates. ... // An ion is an atom or group of atoms with a net electric charge. ...

Plasma osmolality can be approximated with the following formula:

 Plasma osmolality (mOsm/Kg) = 2([Na+] + [K+]) plasma + [BUN] + [Glucose] 

As cell membranes in general are freely permeable to water, the osmolality of the extracellular fluid is approximately equal to that of the intracellular fluid. Therefore, plasma osmolality is a guide to intracellular osmolality. Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... A girl in a swimming pool full of water Water (from the Old English waeter; c. ...

Osmolality increases with dehydration and decreases with overhydration. In normal people, increased osmolality in the blood will stimulate secretion of antidiuretic hormone (ADH). This will result in increased water reabsorption, more concentrated urine, and less concentrated blood plasma. A low serum osmolality will suppress the release of ADH, resulting in decreased water reabsorption and more concentrated plasma. Dehydration is the removal of water (hydor in ancient Greek) from an object. ... Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is a peptide hormone produced by the hypothalamus, and stored in the posterior part of the pituitary gland. ... Urine is liquid waste excreted by the kidneys and is produced by the process of filtration. ...