Vertebrates can accumulate large amounts of waste in their tissues, organs, and blood. To prevent harmful substances from remaining in the body, waste removal is accomplished through a process known as excretion. During this process, waste is discharged through urine, sweat, and other means.
Excretion takes place with the help of four body systems. In the urinary system, the kidneys work to rid the body of water and toxins. They also remove electrolytes and nitrogen compounds. By ridding the body of carbon dioxide waste through respiration, the lungs form the respiratory lever of the excretory system.
Like the kidneys, the skin helps the body excrete nitrogen, water, and electrolyte wastes from the integumentary system. The sweat excreted from the skin contains wastes such as lactic acid and urea. Another purpose of sweat excretion from the skin is to maintain body temperature and homeostasis. The digestive system also plays an important role in the excretory process. The intestine is responsible for removing bile pigmentation, heavy metal salts, and other digestive waste.
Waste exists in various forms. Dead cells and sweat are the most common waste excreted by the skin. Liquid and solid wastes leave the body through digestion in the form of urine and feces. Carbon dioxide and other gases excreted by the lungs are in gaseous form. The lungs also excrete mucus through mucociliary excretion.
The excretion process is vital to the health and well-being of humans and other creatures. The waste found in the body is poisonous and without proper detection can easily lead to death. The excretory system finds these wastes and removes them, allowing the body to remain healthy and functional.
In plants, waste does not accumulate as much as in mammals and other vertebrates. The excretion method used by plants generally consists of the simple diffusion of residual gases in the surroundings of the organism. Like humans, vertebrates excrete waste through the skin, lungs, and urethra with the help of the kidneys and lungs.
The body's waste removal processes may malfunction or cease if the excretory organs fail. Medication and organ replacement can sometimes remedy such dysfunction. Long-term manual treatments, such as dialysis, can sometimes be completed when an organ, such as the kidney, permanently fails. If not replaced or treated properly, excretory failure can lead to serious illness and death.
Many people refer to defecation as excretion. However, the use of the term in this way is incorrect. Although feces itself contains waste and its release is part of the excretion process, defecation itself is not considered waste elimination. Instead, it primarily refers to the elimination of indigestible food.