The urinary and excretory systems remove waste from the body. Several organs are involved in these processes, including the liver, kidney, bladder, skin and lungs. Disorders of these organs can lead to dysfunction of excretion.
Liver
The liver removes protein units called amino acids from the circulatory system. These amino acids undergo a chemical reaction, resulting in urea production. Urea leaves the liver via the circulatory system. The circulatory system transports urea to the kidneys for excretion in urine.
Kidneys
The kidneys filter blood, removing waste products. Nephrons are the main unit of the kidney responsible for this filtration process. A nephron contains a tubular vessel called the glomerulus. The glomerulus and tubules filter wastes as the blood circulates through the kidney, leaving normal proteins and cells in the blood vessel. The kidneys determine the levels of phosophorus, potassium and sodium for the circulatory system. Excessive amounts result in filtration and deficient amounts do not activate the filtration process. The end product is excretion of urine through the ureters.
Bladder
The bladder collects urine from the ureters. This sac is composed of muscle and elastic tissue. As urine accumulates, the bladder expands like a balloon. Bladder expansion results in a sensation that signals a person to urinate. The muscle tissue of the bladder contracts and squeezes urine into the urethra, a tubular structure for excretion. The urethra transports the urine outside the body in a process called urination.
Lungs
The lungs undergo excretion of gases, rather than fluids. Within lung tissue, an important gas exchange takes place. Carbon dioxide is exchanged with oxygen. The circulatory system transports carbon dioxide to the lungs. Carbon dioxide is a waste product from procuring energy from nutrients. As blood circulates through the lungs, carbon dioxide is released into the airway and excreted during exhalation.
Skin
The skin contains glands that produce sweat. According to the National Institutes of Health, a person has as many as 4 million sweat glands. In a process called perspiration, the body releases a salty liquid on the skin's surface. High activity level and temperatures activate this process. Perspiration cools the body through evaporation of sweat.
Considerations
Several disorders can afflict the urinary system, including benign prostatic hyperplasia, painful bladder syndrome, kidney stones, prostatitis, proteinuria, renal failure, urinary tract infections, urinary incontinence and urinary retention. Dysfunction of the excretory system includes excessive or deficient sweating, blood in urine and abnormal blood laboratory results.
