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Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates , this is primarily carried out by the lungs , kidneys , and skin . [ 1 ] This is in contrast with secretion , where the substance may have specific tasks after leaving the cell .
Egestion (Excretion): Removal of undigested materials from the digestive tract through defecation. Underlying the process is muscle movement throughout the system through swallowing and peristalsis. Each step in digestion requires energy, and thus imposes an "overhead charge" on the energy made available from absorbed substances.
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland.In contrast, excretion is the removal of certain substances or waste products from a cell or organism.
Uricotelism is the excretion of excess nitrogen in the form of uric acid. [4] Uricotelic animals include insects , birds and most reptiles . Though requiring more metabolic energy to make than urea, uric acid's low toxicity and low solubility in water allow it to be concentrated into a small volume of pasty white suspension in feces, compared ...
Occurring between meals, the migrating motor complex is a series of peristaltic wave cycles in distinct phases starting with relaxation, followed by an increasing level of activity to a peak level of peristaltic activity lasting for 5–15 minutes. [6] This cycle repeats every 1.5–2 hours but is interrupted by food ingestion.
Only the organs specifically used for the excretion are considered a part of the excretory system. In the narrow sense, the term refers to the urinary system . However, as excretion involves several functions that are only superficially related, it is not usually used in more formal classifications of anatomy or function.
A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase). The level of acid secretion during these times is regulated by body weight, individual, number of parietal cells, and time of day. Acid secretion is lowest in the morning before awakening and highest at night. [2]
The opening between the lips is termed the oral fissure, and the opening into the throat is called the fauces. [9] At either side of the soft palate are the palatoglossus muscles which also reach into regions of the tongue. These muscles raise the back of the tongue and also close both sides of the fauces to enable food to be swallowed.