For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the eyepiece with the plano (flat) side facing the eye.
BUN redirects here. For other uses, see Bun (disambiguation). The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain between 6 and 20 mg of urea nitrogen per 100 ml (6â20 mg/dL) of blood.
384,845 Helpful Votes. A. Blood urea nitrogen (BUN) is a product of metabolism that is excreted in the urine. It is measured in the blood as an indirect measure of how well the kidney is functioning. Increased BUN levels in the blood may indicate early kidney damage, meaning the kidneys aren't effectively excreting BUN.