EXCRETORY SYSTEM The excretory system is a biological system that removes excess, unnecessary or dangerous materials from an organism. It is responsible for the elimination of oxygen waste products of metabolism as well as other nitrogeneous materials. Since the normal operation of most biological systems creates waste, the excretory system is not necessarily distinct from other systems. Instead, it often represents the various excretory processes of several different systems. Excretory functions Every organism, from the smallest protist to the largest mammal, must rid itself of the potentially harmful by-products of its own vital activities. This process in living things is called elimination, which may be considered to encompass all of the various mechanisms and processes by which life forms dispose of or throw off waste products, toxic substances, and dead portions of the organism. Egestion is the act of excreting unusable or undigested material from a cell (as opposed to metabolized waste), as in the case of single-celled organisms, or from the digestive tract of multi-cellular organisms. As defined above, elimination broadly defines the mechanisms of waste disposal by living systems at all levels of complexity. The term may be used interchangeably with excretion, though not all elimination necessarily takes place in the excretory system. Component organs Skin The skin is another part of the excretory system: it eliminates sweat that helps cool the body and regulate the concentration of salt. The salt helps evaporate the water, cooling off the skin. Liver The liver is an organ of the digestive system. It also helps in excreting wastes from the body in a variety of processes. Laboratory analysis reveals a high concentration of a small organelle called a peroxisome, responsible for breakdown of several toxic substances. It also takes in nitrogenous wastes and converts them to urea to reduce their toxicity. The liver absorbs drugs and other poisonous substances in the blood and changes their chemical structure to make them less toxic and easier to digest. This waste product is called bile and is excreted to the digestive tract, facilitating digestion of fats while also disposing of waste. Kidneys The key organs in the excretory system of vertebrates. (See protonephridia system for Platyhelminthes, metanephridia for Annelida, or the Malpighian tubes for insects and terrestrial arthropods.) The kidneys are placed on either side of the spinal column near the lower back. They are primarily responsible for filtering blood by removing nitrogenous wastes, though they also regulate blood pressure in a process called osmoregulation and also assist with the production of red blood cells. Secretion The separation, elaboration, and elimination of certain products arising from cellular functions in multi-cellular organisms is called secretion. Though these substances may be a waste product of the cell producing them, they are frequently useful to other cells of the organism. Examples of secretions are the digestive enzymes produced by intestinal and pancreatic tissue cells of vertebrate animals, the hormones synthesized by specialized glandular cells of plants and animals, and sweat secreted by glandular cells in the skins of some humans. Secretion implies that the chemical compounds being secreted were synthesized by specialized cells and that they are of functional value to the cell. The disposal of common waste products should not, therefore, be considered to be of a secretory nature. The excretory system is very important to your body and only has a few parts. In a similar way to removing solid waste from your body, you must also get rid of fluids. You know the results of the excretory system as urine. Urine is the result of the excretory system balancing the amount of water and salts in your body. We said the system is small. Your kidneys are the core organs involved in the excretory system. Related body parts include the ureters, bladder, and urethra. Once the urine passes through your urethra, that's it, it's out of your body. INTERACTING WITH OTHER SYSTEMS The excretory system is a close partner with both the circulatory and endocrine system. The circulatory system connection is obvious. Blood that circulates through the body passes through one of the two kidneys. Urea, uric acid, and water are removed from the blood and most of the water is put back into the system. The endocrine system is the major controller of the excretory system. As levels of compounds and fluids are monitored, kidney function must be constantly altered to provide the best internal environment for your cells. If you drink too much water, hormones are released that allow for more urine production. If you are dehydrated, less urine will be produced. The kidneys are also tied to the endocrine system with the adrenal gland position on the top of each kidney. The adrenals release adrenaline into your body. DISEASES OF THE EXCRETORY SYSTEM 1.Bladder cancer Bladder cancer develops when cells lining the urinary bladder become abnormal and grow uncontrollably, forming tumors. It is the fifth most common cancer in the United States. The disease is three times more common in men than woman. Most cases of bladder cancer are found in people who are fifty to seventy years old. The exact cause of bladder cancer is unknown. However, smokers are twice as likely as nonsmokers to get the disease. Workers who are exposed to certain chemicals in the dye, rubber, leather, textile, and paint industries are also believed to be at a higher risk for developing bladder cancer. One of the first warning signs of bladder cancer is blood in the urine. Painful urination, increased frequency of urination, and a feeling of having to urinate but not being able to are additional signs of bladder cancer. 2.Cystitis (sis-TIE-tis): Inflammation of the urinary bladder caused by a bacterial infection. 3.Glomerulonephritis (glah-mer-u-lo-ne-FRY-tis): glomeruli in the renal corpuscles of the kidneys. Inflammation of the 4.Kidney stones: Large accumulations of calcium salt crystals from urine that may form in the kidneys. 5.Pyelonephritis (pie-e-low-ne-FRY-tis): Inflammation of the kidneys caused by a bacterial infection. 6.Urethritis (yer-i-THRY-tis): Inflammation of the urethra caused by a bacterial infection. 7.Urinary incontinence (YER-i-nair-ee in-KON-tinence): Involuntary and unintentional passage or urine. If bladder cancer is diagnosed, the three standard methods of treatment are surgery, radiation therapy, and chemotherapy. During surgery, surgeons may remove the tumor, part of the bladder containing the tumor, or the entire bladder and adjoining organs (the prostate gland in men; the uterus, ovaries, and fallopian tubes in women). Radiation therapy (using X rays or other highenergy rays to kill any remaining cancer cells and shrink any tumors) is generally used after surgery. Chemotherapy (using a combination of drugs to kill any remaining cancer cells and shrink any tumors) may also be given after surgery. When detected early and treated appropriately, bladder cancer can be cured. In those people who have sought early treatment, at least 94 percent survive five years or more. However, when the disease has spread to nearby tissues, the survival rate drops below 50 percent. 7. Glomerulonephritis Glomerulonephritis is the inflammation of the glomeruli in the renal corpuscles. It is generally caused by a bacterial infection elsewhere in the body, mostly in the throat or skin. In children, it is mostly associated with an upper respiratory infection, tonsillitis, or scarlet fever. During a bacterial infection, the body produces antibodies or substances that help protect the body against foreign invaders. Glomerulonephritis develops when antibodies and the bacteria they attach to accumulate in the glomeruli, producing inflammation. If left untreated, the glomeruli are soon replaced by fibrous tissue and waste products cannot be effectively filtered from the blood. The kidneys become enlarged, fatty, and congested.