The structures that together form the heart, blood vessels and blood, is called the circulatory system, which has as its main function the transport or circulation of all nutrients, waste, oxygen, antibodies, electrolytes, among other substances through the blood., to all cells and tissues of the body. Also, it can regulate body pH and body temperature.
Thus, the heart represents that motor or pump in charge of keeping the blood in circulation, the blood vessels represent the channels through which the blood passes, the latter being the means of transport.
It is understood then, as a circulatory system that "internal sea" that living beings have, which moves throughout our body, transporting substances and waste, through its liquid (blood).
In this way, the circulatory system supports all the organs of the body. In the case of the lungs, they are benefited, since the circulatory system acts as a transport of the oxygen that they send to the tissues and in the opposite direction, the carbon dioxide that they send to the lungs.
Unlike humans, animals have two types of circulatory systems, the open and the closed.
On the one hand there are many of the invertebrates, including arthropods, such as spiders, insects, crustaceans, mollusks, snails and clams, which have one or two hearts, accompanied by a network of blood vessels and a large open space that it can occupy up to 40% of the body volume, called hemocele.
On the other hand, are invertebrates such as worms of earth and mollusks very active, such as octopus and squid and vertebrates (including being human) that have a closed circulatory system, in which the blood circulation depends clearly of the heart and blood vessels. Having a much faster flow and a more effective displacement of nutrients and waste, thus generating a higher blood pressure than that generated by the open circulation system.
The circulatory system is closely related to the nervous system, which together form a neurovascular bundle. Both represent a structure that is present throughout the body, which move and elongate, through the movements made by the individual.
However, the circulatory system is more understandable, but less solid than the nervous system, since it only contains one element (blood).
