Final answer:
Urine is primarily composed of water, but also includes urea, creatinine, and other metabolic waste components. The presence of substances in urine can indicate kidney-related issues or injury.
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.