Excretion is the process by which metabolic waste is excreted from the body. In vertebrates, it is primarily carried out by the lungs, kidneys, and skin. The process contrasts with secretion, where a substance can have specific tasks after leaving the cell. Excretion is an important component in all forms of life. For example, in mammals, urine is excreted through the urethra, which is part of the excretory system. In unicellular organisms, waste is ejected directly through the surface of the cell.
What is the biological significance of excretion?
Every organism, from the smallest protist to the largest mammal, must rid itself of potentially harmful by-products of its life. This process in living beings is called elimination, which can be seen as encompassing all the various mechanisms by which life forms dispose of or discard waste, toxic substances, and dead body parts. The nature of the process and specialized structures developed for waste disposal varies greatly depending on size and complexity.organism.
Terminology
Four terms are commonly associated with waste disposal processes and are often used interchangeably, though not always correctly: excretion, secretion, excretion, and excretion.
Excretion is a general term referring to the separation and ejection of waste products or toxic substances from the cells and tissues of a plant or animal.
The separation, development and elimination of certain products resulting from the cellular functions of multicellular organisms is called secretion. While these substances may be a waste product of the cell that produces them, they are often beneficial to other cells in the body. Examples of secretion are digestive enzymes produced by cells of the intestinal and pancreatic tissue of vertebrates, hormones synthesized by specialized glandular cells in plants and animals, and sweat secreted by glandular cells in the skin of some mammals. Secretion implies that secreted chemical compounds are synthesized by specialized cells. They have a functional value for the body. Therefore, the disposal of ordinary waste should not be considered secretory.
Isolation is the act of removing unusable or undigested material from a cell (both in the case of unicellular organisms and from the digestive tract of multicellular animals).
Decrease - This removal broadly defines the mechanisms of waste disposal by living systems at all levels of complexity. The term may be used interchangeably with emphasis.
Cells
Cellular respiration is when several chemical reactions take place in the body. They are known as metabolism. These chemical reactions produce waste products such as carbon dioxide, water, s alts, urea, and uric acid. The accumulation of these waste products beyond the level within the body is harmful. The excretory organs remove them. Excretion is the process of removing metabolic waste from the body.
In plants
Green plants produce carbon dioxide and water as respiratory products. In green plants, carbon dioxide released during respiration is used during photosynthesis. Oxygen is a by-product generated during photosynthesis and exits through stomata, root cell walls, and other pathways. Plants can get rid of excess water through transpiration and gutting.
The leaf has been shown to act as an "excretophore" and, in addition to being the primary organ of photosynthesis, is also used as pathways for the excretion of toxic waste products through diffusion. Other waste products emitted by some plants (resin, juices, latex, etc.) are forced out from within the plant by the hydrostatic pressure inside the plant and by the absorbing forces of the plant cells. However, during the pre-shedding phase, the metabolic rate of the leaf is high. Plants also release some waste into the soil around them. In this case, excretion is a passive process, since it does not needextra energy.
Aquatic animals
Aquatic animals usually release ammonia directly into the environment, as this compound has a high solubility. In addition, there is enough water for dilution. In land animals, ammonia compounds are converted into other nitrogenous materials, since there is less water in the environment and ammonia itself is toxic.
Birds
Excretion in birds occurs through the nitrogenous waste products of uric acid in the form of a paste. Although this process is metabolically more expensive, it allows for more efficient water retention. In addition, it is easier to store in an egg. Many species of birds, especially seabirds, can also excrete s alt through special nasal s alt glands, a saline solution that exits through the nostrils in the beak.
Insects
In insects, the Malpighian tubule system is used to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transfers the waste to the intestine. Metabolic waste is then excreted from the body along with faeces.
In animals
In animals, the main excretory products are carbon dioxide, ammonia (in ammoniotelics), urea (urethotelics), uric acid (uricothelins), guanine (in arachnids) and creatine. The liver and kidneys purify the blood of many substances (for example, by renal excretion), and the purified substances are then excreted from the body with urine and feces.
Water loss through excretion duringthe passage of water molecules through a thin membrane containing pores too large to carry molecules is called osmosis, a process that occurs spontaneously and does not require energy. This process can be reversed by applying hydrostatic pressure to the solution.
The level of hydrostatic pressure at which there is no net movement of water in any direction across the membrane is called the osmotic pressure of that particular solution; the greater the concentration of dissolved molecules, the greater the osmotic pressure and the greater the force required to remove water from the solution.
