Elimination vs Excretion
Elimination is a process by which waste and indigestible material are removed from the body. Excretion can be considered as a method of elimination, but it involves only in the removal of metabolic waste.
What is Excretion?
Excretion is the process by which wastes produced in the body are removed from the body. There are 3 main organs in the human body that are involved in excretion. They are the kidneys, lungs and skin. Lungs help to remove carbon dioxide from the body and the skin removes sweat by evaporation. Nitrogenous wastes are excreted from the body and excretion is the removal of waste produced resulting from the metabolism in the body. Many toxic waste products are formed during metabolism. If not excreted, it is difficult to maintain the chemical composition within the body and for the metabolic process to take place. The waste products that are excreted from the body are ammonia, urea, uric acid, bile pigments and carbon dioxide. Removal of nitrogenous waste is termed as nitrogenous excretion. Osmoregulation is the maintenance of a constant osmotic pressure within the body by regulating the amount of water and ion concentration. It is important to regulate ions like sodium ions, potassium ions, calcium ions and chloride ions. Nitrogenous wastes are formed by the breakdown of proteins, nucleic acids and excess amino acids. Immediate nitrogen waste product ammonia is derived from NH2 formed during protein metabolism. Ammonia is extremely toxic. Therefore, it has to be removed from the body or otherwise converted to urea or uric acids, which are not harmful. The exact nature of the excretory product is determined by the habitat of the animal, the amount of water available for the animal, the degree of water regulation loss, presence or absence of certain enzymes. Protozoans and coelenterates have no excretory organs. Flat worms have flame cells. Annelids have metanephridia. Insects and some arthropods have malpighian corpuscles. Crustaceans have green gland and maxillary glands. Vertebrates have kidneys.
What is Elimination?
Elimination involves in the removal of wasted and indigestible food material from the body. Elimination includes defecation. Defecation is the removal of indigestible material. Feces are produced in the large intestine. It is yellowish brown semi solid and is sent out through the anus. Control of defecation is by behavioral adjustments. Usually the rectum is empty. Contents in the sigmoid colon are forced in to the rectum by mass movement. In the rectum, the nerve endings in the walls are stimulated by stretch. In infants defecation occurs by reflex action (involuntary). In response to distention of the rectum by feces, the nerve endings in the walls are stimulated, and the anal sphincter opens, defecation takes place. But in adults it is under voluntary control. Brain can inhibit the reflex until such time, as it is convenient to defecate.
What is the difference between Excretion and Elimintion?
• Excretion involves only in the removal of metabolic waste from the body, whereas elimination is involved in removal of waste and indigestible food material from the body.
• Elimination involves removal of indigestible food material from the body but excretion does not involve in the removal of indigestible food material from the body.
• Digestive system involves in the elimination process, but the digestive system does not involve as a main system in the excretion process.
• Excretion can be considered as a method of elimination, but elimination cannot be considered as a method of excretion.