The circulatory system of amphibians (frogs, newts, salamanders, worms) is markedly different from that of reptiles (snakes, turtles, crocodiles, lizards) and crustaceans (crayfish). Amphibians are an intermediate link between crustaceans and reptiles.
The circulatory system of amphibians
In amphibians, the circulatory system is closed. The heart, consisting of two chambers, is possessed only by lungless salamanders. All other amphibians have a three-chambered heart. The circulatory system of representatives of this class of animals consists of two circles of blood circulation - small and large. It is curious that the pulmonary circulation arose as a result of the appearance of pulmonary respiration in these animals. The heart in amphibians consists of two atria and one ventricle.
The blood of these animals in different atria is different: in the right it is mixed (more venous), and in the left it is arterial. Amphibians also have a number of arteries responsible for blood transport: for example, the pulmonary arteries carry venous blood to the skin and lungs, and sleepy arteries supply arterial blood to the upper body (for example, to the head). The aortic arches are designed to transport mixed blood to all other organs of amphibians. It should be noted that the body temperature of amphibians is a variable value depending on the ambient temperature, because amphibians are cold-blooded animals.
Reptile circulatory system
The circulatory system of reptiles is similar to that of amphibians, but it also has its own differences. The heart of reptiles consists of two atria that open into the ventricle. In all reptiles, except for crocodiles, an incomplete septum separates the ventricle. This allows their blood from the atria to partially mix. The pulmonary artery and two aortic arches independently begin in the heart ventricle and join in the dorsal aorta, while the arteries extending from it supply mixed blood to other organs of the reptile's body. Such an organization of the blood supply allows these animals to be most adapted to certain living conditions.
Crustacean circulatory system
In crustaceans, the circulatory system is open. This distinguishes them from the other two above animal classes. If we compare the circulatory system of crustaceans with that of reptiles and amphibians, then in the former it is the most primitive. The blood is set in motion by the beating of a heart placed near the gills. Only higher crustaceans have blood vessels. In all other representatives of this trivial group of animals, blood flows freely through the cavities located next to the internal organs. Often, special respiratory pigments dissolve in such blood.
