The Urinary system

The urinary system is the organ system that makes, stores, and gets rid of urine. It includes two kidneys, two ureters, the bladder, and the urethra. The main function of the urinary system is to filter waste products and excess water from the blood and remove them from the body. Urine is the liquid waste product of the body that is excreted by the urinary system. Recall that in the excretion process, other organs as skin and lungs take part in it.Organs of the urinary system
Kidneys
The kidneys are a pair of bean-shaped, reddish brown organs about the size of a fist. They are located just above the waist at the back of the abdominal cavity, on either side of the spine. Located on top of each kidney is an adrenal gland.
The kidney has three layers, the outer layer is the renal cortex, and the middle layer is the renal medulla. The inner layer, the renal pelvis is urine is collected and is funnelled into the ureter
From the aorta, the renal arteries carry blood to the kidneys to be filtered, then the renal veins carry the filtered blood away from the kidneys to the inferior vena cava.
Ureters
From the kidneys, urine enters the ureters, which carry it to the bladder. Each ureter is a muscular tube about 25 centimeters long.
Bladder
The bladder is a hollow organ that stores urine. It can stretch to hold up to 500 milliliters. When the bladder is about half full, the stretching of the bladder sends a nerve impulse to the sphincter that controls the opening to the urethra. In response to the impulse, the sphincter relaxes and lets urine flow into the urethra.
The urethra is a muscular tube that carries urine out of the body. Urine leaves the body through another sphincter in the process of urination. This sphincter and the process of urination are normally under conscious control.
As in other organ systems here you have a video for kids but it is very clear.