Write short notes on Urine?

The concentrated filtrate produced by the kidney is called urine, and is composed mainly of water, urea, toxins, and mineral salts. Urine from the collecting ducts goes to the renal pelvis and then into a narrow tube called the ureter. The ureter leads from each kidney to the urinary bladder, where it is stored until it is expelled from the body through the urethra, a short tube opening through the penis in males and just anterior to the vagina in females.

One of the two sphincter muscles involved in urination is controlled by the voluntary or conscious nervous system. Adult humans urinate two to three liters per day, while the kidneys filter 180 liters per day.