Four-chambered hearts have amphibians and reptiles: examples

Our planet is densely populated by animals of various classes, detachments and species. Scientists study their structure and the functional significance of individual organs. About the heart of amphibians and reptiles, read in the article.

How did the heart of the three cameras become a four-chamber?

Vertebrates came to the land due to the fact that their pulmonary breathing began to develop intensively. The circulatory system began to rebuild. Fish, breathing gills, have one circle of circulation of blood, their heart consists of only two chambers. They can not live on land.

The three-or four-chambered heart has terrestrial vertebrates. They are distinguished by the presence of two circles of blood circulation. Their constant habitat is land. The body with three chambers has amphibians and reptiles. Although some reptiles have incomplete division into four parts. The development of this four-chambered heart in the process of evolution occurred in parallel in mammals, birds and crocodiles.

Reptiles and amphibians

These two classes of animals have two rounds of circulation of blood and a heart consisting of three chambers. Only one reptile has an inferior but four- chambered heart. It's a crocodile. A full-fledged cardiac organ first appeared in primitive mammals. In the future, the heart with such a structure was inherited by descendants of dinosaurs - birds. It was transmitted by inheritance and modern mammals.

Birds

Four-chambered hearts are feathered. Birds are characterized by a complete dissociation of the circulation circles: large and small, as in humans, when there is no mixing of blood - arterial and venous. The right and left halves of the organ are completely separated.

Birds have a four-chambered heart, Its structure is represented by two atria and the same number of ventricles. Venous blood enters the ventricle through the right atrium. From it occurs the divergence of the pulmonary artery, which is divided into the left and right branches. As a result, venous blood appears in the corresponding lung. At this time, the blood in the lungs is oxidized and enters the left atrium. This circulation is called its small circle.

A large circle of circulation of blood originates from the left ventricle. From it departs one single vessel, which is called the right arch of the aorta, which immediately at the exit from the heart separates two nameless arteries: the left and right arteries. The aorta itself unfolds in the area of the right bronchus and runs parallel to the spinal column already as a dorsal aorta. Each nameless artery is divided into sleepy and subclavian. The first goes to the head, and the second again divides into the thoracic and humeral. Large arteries leave the dorsal aorta. Unpaired are designed to supply blood to the stomach and intestines, and paired - to the hind limbs, the pelvic cavity organs and the muscles of the peritoneal walls.

Four-chambered hearts have birds, it is distinguished by the fact that in birds the movement of blood is carried out mainly on vessels of large sizes, and only a small part of it enters the renal capillaries. Birds are distinguished by the presence of a large heart with frequent contractions and entry into the organs of only pure arterial blood. This allowed the birds to be considered warm-blooded animals.

The circulatory system of mammals

Mammals have a four-chambered heart, like a human being or a bird. Its formation with complete separation of circulation circles of blood is caused by the necessity of developing such quality as warm-bloodedness. This is explained as follows: warm-blooded animals experience a constant need for oxygen, which only pure blood of arteries with a large amount of oxygen is able to satisfy. Provide it with an organism capable of only a four-chambered heart. A mixed blood of vertebrates, in which the heart has three chambers, is not capable of giving the desired body temperature. Therefore, such animals are called cold-blooded animals.

Due to the presence of complete partitions, the blood does not mix. On a large circle of circulation, only arterial blood flows, which is adequately supplied to all organs of the mammal, which facilitates the acceleration of metabolism. This process helps maintain the temperature at a constant level. The four-chambered heart has mammals, birds and other classes of animals, which need a constant and stable body temperature. Now the environment does not affect them.

Lizards

In fact, the heart of these reptiles has three chambers with two atria and one ventricle. But the principle of his work makes it possible to assert that the four-chambered heart has lizards. This phenomenon has the following explanation. The venous cavity is filled with oxygen-poor blood, the source of which is the right atrium. Arterial blood, enriched with oxygen, comes from the opposite atrium.

Pulmonary artery and both arches of the aorta are reported. It would seem that the blood should completely mix. But this does not happen, since the presence of a muscle flap in combination with a two-phase contraction of the ventricle and further work of the heart prevent the mixing of blood. It is available, but in very small quantities. Therefore, in terms of functional significance, the three-chambered heart of lizards is similar to the four-chamber one.

Reptiles

The crocodile has a four-chambered heart, although the circulation circles are not completely separated by a septum. The reptile body (the heart), which is responsible for supplying the whole body with food through the blood, has a special structure. In addition to the pulmonary artery, which extends from the ventricle on the right side, there is an additional left one. According to it, most of the blood enters the digestive system.

Between the two arteries, right and left, the heart of the crocodile has a hole. Through it, the blood from the veins has the opportunity to fall into a large circle of circulation, and vice versa. Scientists have long believed that the heart of a reptile has a transitional character on its way to developing a full-fledged heart from four chambers, as in warm-blooded mammals. But this is not so.

Turtles

The system of blood vessels and heart in these reptiles is the same as in other reptiles: a heart with three chambers, connected with each other by veins and arteries. The content of insufficiently oxidized blood increases when the external pressure increases. This can happen when the animal dives or moves quickly. The frequency of cardiac contractions decreases, although the concentration of carbon dioxide significantly increases.

Four-chambered hearts have turtles, although the physiological structure of the body has only three chambers. The fact is that the heart of the turtle is characterized by an incomplete ventricular septum around which the blood functions, having a different amount of oxygen.