Final answer:
Urine is a liquid byproduct of the body that contains urea, creatinine, and other waste components. Injury or infection of the kidneys can affect the composition of urine.
Step-by-step explanation:
Urine is a liquid byproduct of the body secreted by the kidneys through a process called urination and excreted through the urethra. The normal chemical composition of urine is mainly water content, but it also includes nitrogenous molecules, such as urea, as well as creatinine and other metabolic waste components. Other substances may be excreted in urine due to injury or infection of the glomeruli of the kidneys, which can alter the ability of the nephron to reabsorb or filter the different components of blood plasma.