excretory system

The excretory system is an organ system that performs the function of excretion, the bodily process of discharging nitrogeneous wastes. It is responsible for the elimination of the nitrogeneous waste products of metabolism as well as other non-useful nitrogeneous materials. Lungs are two organs localized on each side of the thorax. They are constituted by pulmonary alveoli. They are responsible for converting oxygen into carbon dioxide, but to maintain the organism's cells can take the oxygen through passive diffusion from the bloodstream and use it in its own metabolism, thus producing carbon dioxide that will be further excreted when passing through alveoli circulation.

The process by which animals rid themselves of waste products and of the nitrogenous by-products of metabolism. Through excretion organisms control osmotic pressure—the balance between inorganic ions and water—and maintain acid-base balance. The process thus promotes homeostasis, the constancy of the organism's internal environment.

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. The nature of the process and of the specialized structures developed for waste disposal vary greatly with the size and complexity of the organism.

Four terms are commonly associated with waste-disposal processes and are often used interchangeably, though not always correctly: excretion, secretion, egestion, and elimination.

Excretion is a general term referring to the separation and throwing off of waste materials or toxic substances from the cells and tissues of a plant or animal.

The separation, elaboration, and elimination of certain products arising from cellular functions in multicellular 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 mammals. Secretion implies that the chemical compounds being secreted were synthesized by specialized cells and that they are of functional value to the organism. The disposal of common waste products should not, therefore, be considered to be of a secretory nature.

Egestion is the act of excreting unusable or undigested material from a cell, as in the case of single-celled organisms, or from the digestive tract of multicellular animals.

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. The waste then travels to anus and is released.


The skin is another part of the excretory system, containing sweat that help regulate the concentration in one’s body while also keeping him or her cool. The salt helps evaporate the water, cooling off the skin. Sweat is excreted through sweat glands. There are two types of sweat glands: eccrine sweat glands and apocrine sweat glands. The basic purpose of skin is to provide a waterproof, protective, covering for the body's complex internal environment. The skin also plays a key role in helping to maintain the circulatory and nervous system.

Eccrine sweat glands

The eccrine sweat glands secrete mostly water and salt and are used by the body for temperature control. These glands are located all around the body but are most profuse around the soles of the feet, palms of the hands, and the forehead.


The liver is an accessory of the digestive system.It weighs more than 1.5 kg. It is the body's largest and most complicated organ and is shaped like a pyramid. It also helps in excreting wastes from the body.

The liver absorbs drugs and other poisonous substances in the blood. It takes part in several hundred chemical reactions that control the composition of the blood and supply the needs of other organs.It changes the chemical structure of these substances are then excreted in the bile. The bile is secretion of the liver. It makes digestion of fats easier and also carries away waste production.


The most important organs of the excretory system are the kidneys. The kidneys are placed on either side of the spinal column near the lower back. The kidneys are bean-shaped and they have an important job. They are responsible for removing wastes from the blood and they also keep your blood pressure in check and help with the making of red blood cells. The kidneys filter the blood and remove any wastes. The Kidney does this via its three lauers which are the Cortex, the medulla and the pelvis. In the Cortex and Medulla there are Nephrons. These Nephrons comprise of a Glomerulus (bundle of capilaries), a Bowman's Capsule, a Proximal Convoluted Tubuale, the descending and ascending Loop of Henle, the Distal Convoluted Tubual and Collecting Ducts. The collecting ducts come together in the Pelvis. When your body gets ready to pass waste products, it goes through the kidneys and mixes with water and urine. Then, the waste travels into the bladder through tubes. These tubes are called Ureters. Now, the bladder holds all of that urine until it feels so full that you need to get rid of it. That's called urination. When this happens, a tube called the Urethra takes the urine to the outside of the body. It also produces Bile.


Bile is a substance secreted by the abdomen and used for breaking wastes, with the help of estrogen. It is composed of water, cholesterol, lecithin, bicarbonate ions, bile salts, and pigments. Bile is a strong basic substance, classified as alkaline. It is released through bile ducts in the liver. Bile is a digestive chemical that is produce in the liver, stored in the gall bladder,and secreted in the small intestine. The kidney's main roles are to control the blood PH, filter all kind of wastes and remove urea from the blood and produced in to urine.

Bile is capable of breaking down fats.

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