THe urinary/excretory system produces, stores, and eliminates urine, the fluid waste excreted by the kidneys. The kidneys make urine by filtering wastes and extra water from blood. Urine travels from the kidneys through two thin tubes called ureters and fills the bladder. When the bladder is full, a person urinates thorugh the urethra to eliminate the waste. The urinary system works with the lungs, skin, and intestines to maintain the balance of chemicals and water in the body. The urinary system is made up of:
All of these components of the filter blood and remove waste from the body in the form of urine. The kidneys are bean-shaped organs that are located just below the rib cage in the middle of the back. The kidneys remove urea, which is a waste product formed by the breakdown of proteins, from the blood through small filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, mixed together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney. From the kidneys, urine travels down two thin tubes, called ureters, to the bladder. Muscles in the ureter walls continuously tighten and relax to force urine away from the kidneys. A backup of urine can cause a kidney infection. Small amounts of urine are emptied into the bladder from the ureters about every 10 to 15 seconds. The bladder is a hollow, balloon-shaped organ that is located in the pelvis. It is held in place by ligaments attached to other organs and the pelvic bones. The bladder stores urine until the brain signals the bladder that the person is ready to empty it. A normal, healthy bladder can hold up to 16 ounces (almost half a liter) of urine comfortably for two to five hours. To prevent leakage, circular muscles called sphincters close tightly around the opening of the bladder into the urethra, the tube that allows urine to pass outside the body.
Here are all of the main organ systems of the human body and some info about them: