El excretory system of animals it is characterized because if the excretory organ is the nephridium (in the case of invertebrates), which would be the organ analogous to the kidneys that humans have, this entry will explain the mechanisms of excretion that this system has in animals and how it is in invertebrates and in vertebrates.
excretory system in animals
The excretory system of animals is called the set of organs that these living beings have to eliminate food waste that cannot be digested by them, feeding and the digestion process also involves the disposal of some particles that do not work for the organism of the animal, that is, they cannot be transformed into energy or nutrients. This is so regardless of the Classification of animals according to their diet.
Generally, this system, through the excretory apparatus, filters the blood of animals and differentiates which substances should be eliminated and which should not, as well as which ingested food particles should be discarded and which should not. This excretory system in animals can be different in each species, clearly there are points in common but it is natural to see differences when the species are so varied and the physical and internal structures have so much diversity of organs and functioning.
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The excretory system is responsible, in principle, for eliminating waste of various types so that the internal organism of the living being is kept in the best conditions and its cellular functioning can continue without any inconvenience. In addition to that, the excretory system in animals allows regulating the levels of substances that the organism has in the body, for example, mineral salts.
It is also responsible for regulating the amount of water in the body and thus influences the control of blood pressure that the individual has. These are the main functions of the excretory system in animals. As for the types of waste that are expelled by it, they are:
- In the first place, the nitrogenous residues that contain ammonia, uric acid, guanine or urea, although this is conditioned by the amount of water that the body has to dispose of them without being harmed by the expulsion.
- There are also metabolic wastes, these can also have nitrogen due to the nucleotide amino acids that a food or prey that the animal has ingested contains. Although also the CO2 of the breath is excreted.
- The dead cells in a certain part are consumed by some species and provide some nutrients for them, but there are remains of them that are microbial that must be expelled from the body so that they do not damage any organ if they remain there for a long time.
- Another type of waste is toxic or non-metabolizable substances, such as water, salts or the toxic parts of a food or liquid that was absorbed by any means.
In addition to that, the excretory systems are responsible for solving some problems of the cells, for example, when the solutes are concentrated in a certain way outside or inside a body membrane. Cells have membranes that allow them to control the entry and exit of water, although this generally occurs freely. Solutes cannot enter and leave freely but must do so by means of carrier proteins specific for them.
When the water enters and bursts the membrane, solutes can enter or when the water that was concentrated inside leaves. When it does not, the excretory system must act to solve the problem (they would be isotonic solutions) and allow cell function to continue normally.
Excretion mechanisms
As for the mechanisms that are used by the excretory system in animals, you can see the integument, the gills or some organs such as the nephridia. Hand in hand with this system works the regulation system of the hormones of the animal's body, so that dehydration does not occur or the body is affected by lack of salts.
- The integument is outside the body and controls the substances that the system has identified to excrete them, some small marine animals have this organ.
- The gills are mainly responsible for excreting CO2, just as the lungs function to excrete CO2.
- Other organs such as the nephridia are responsible for filtering the cells and large proteins that have the substances to be discarded. They are also responsible for absorbing useful substances again before expulsion and pouring the liquid or solid excrement that contains all the particles to be discarded outside the animal's body.
The excretory organs of animals are the nephridium (protoneridium and metanephridium), the nephron (which is an excretory unit of vertebrate animals), the kidney, the ureters, the urinary bladder, and the urine (which is usually a liquid).
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Protonephridia invertebrates
These animals have a fairly simple excretory system that is shaped like a network that extends throughout their body and is connected to the outside through the nephridiopore. This network is made up of tubules that have cells in certain parts that produce a flow current so that the waste goes to the outside, these cells can be flaming or solenocytes. Flatworms are the species that have this type of system.
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metanephridian invertebrates
This type of system is also connected with tubules but these do not form a network, they look like a funnel because they are found in each coelom that the body has and they have openings on each side. The flow of substances to be excreted is caused by the cilia. This type of system is common in the species of the divisions: annelids, arthropods and molluscs.
Arthropods such as crustaceans have green glands as excretory apparatus, these are shaped like sacs and are connected to the bladder by means of a long tubule to the nephridiopore through which they expel disposable substances. Meanwhile other arthropods have tubules that are also connected to the intestine.
Vertebrate excretory system
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mesonephros
The excretory system in animals of this type is characterized by the fact that its excretory system is similar to a kidney, it also has many tubules in the initial part and that are connected to each other forming a section called Bowman's capsule. Adult fish and amphibians are an example of this type of system.
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metanephros
El excretory system of reptiles, Mammals and birds have the kidneys as excretory apparatus, these have tubes called nephrons that also form a section like the previous system, they also have a loop of Henle and a distal convoluted tube through which waste flows to the collecting tubule and finally to the bladder and urethra.