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The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function, though it is inferior to other markers such as creatinine because blood urea levels are influenced by other factors such as diet, dehydration, [35] and liver function.
The excretion of urea is called ureotelism. Land animals, mainly amphibians and mammals, convert ammonia into urea, a process which occurs in the liver and kidney. These animals are called ureotelic. [3] Urea is a less toxic compound than ammonia; two nitrogen atoms are eliminated through it and less water is needed for its excretion.
Uremia is the condition of having high levels of urea in the blood. Urea is one of the primary components of urine.It can be defined as an excess in the blood of amino acid and protein metabolism end products, such as urea and creatinine, which would normally be excreted in the urine.
There are two systems that create a hyperosmotic medulla and thus increase the body plasma volume: Urea recycling and the 'single effect.' Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea.
Measurements of urea and creatinine (Cr) in the blood are used to assess renal function. For historical reasons, the lab test measuring urea is known as "blood urea nitrogen" (BUN) in the US. The BUN:Cr ratio is a useful measure in determining the type of azotemia and will be discussed in each section below.
Metabolism (/ m ə ˈ t æ b ə l ɪ z ə m /, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins, lipids, nucleic acids, and some carbohydrates; and the ...
Blood flows into these capillaries through the afferent arterioles and leaves through the efferent arterioles. The high hydrostatic pressure forces small molecules in the tubular fluid such as water , glucose , amino acids , sodium chloride and urea through the filter, from the blood in the glomerular capsule across the basement membrane of the ...
The urea cycle converts highly toxic ammonia to urea for excretion. [1] This cycle was the first metabolic cycle to be discovered by Hans Krebs and Kurt Henseleit in 1932, [2] [3] [4] five years before the discovery of the TCA cycle. The urea cycle was described in more detail later on by Ratner and Cohen.