The heart is an important organ, without which it can not do any living creature in the world. The circulatory system of birds is arranged in a special way, because flight requires a great effort of the muscles. How is the blood pump of birds to regularly supply them with blood?
This hollow muscular organ in birds and mammals has a similar structure. The main difference is that it four barrel. On the structure of the heart in birds is divided into left and right Atria, and right and left ventricle. Share these departments special valves, consisting of fibro-muscular tissue. The right valve is called the tricuspid, tricuspid it. Left – mitral, its structure folding.
The oxygen saturation in the blood occurs as follows: for the two front and one rear hollow veins the blood to the right atrium, it flows into the right ventricle, then the pulmonary circulation drives the blood through the lungs. Saturated with molecules of oxygen the blood then flows into the left atrium, then into the left ventricle which flows into the main aorta and is carried to all organs and systems.
The principle of operation of the circulatory system
In birds both circulation (large and small) are not connected, and venous blood never mixes with blood. The systemic circulation begins with the right aortic arch.
Leaving the heart, the aorta fills with blood left and right innominate artery, and the blood itself carries on, throwing the right bronchus and descending along the spinal column. Innominate artery pass into the common carotid and subclavian. The dorsal artery are accessory arteries that supply blood to the digestive organs and others that are in the pelvis. They also nourish the lower extremities winged.
The left aortic arch collects venous blood from the head, wing and shoulder muscles in the jugular, brachial and thoracic veins. Then the blood enters the right and left cava and ascends to the right atrium. A number of small veins collect the venous blood from the region of the cloaca, and then they chased her through the portal vein veins of the liver and kidneys.
Of the blood in the kidneys moves through small vessels and capillaries, the other part flows through the major vessels. In the liver the portal vein distributes the blood through the capillaries, and then collects it back into the Vena cava.
Features hearts, birds
- The main attribute of the heart of birds – its relatively large size relative to body mass of the birds themselves. On average, its value reaches 1% of the total weight of the bird. In many species, this figure even more, especially those who are characterized by rapidity of flight and ability to make turns.
- The pulse rate is much higher from the winged human that speaks about the intense work of the heart. Alone, this figure is 200-300 beats per minute (birds of medium size), in-flight heart rate increased to 400-500.
- The smaller the bird, the more her heart beats. At rest the heart rate of small birds is equal to 400-600 beats per minute, and under load can go up to 1000 and more.
- The pressure of blood in the vessels is comparable with the values of the person with hypertension. The maximum numbers reaching up to 200 mm Hg. If you compare the total amount of blood in birds, it is higher than that of reptiles and comparable to mammals.
- The contents of red blood cells is also quite high. Intense blood is enriched with oxygen, in reptiles the oxygen storage capacity is below 2-4 times.
Why are birds such a powerful circulatory system? They have a high metabolism, and blood shall promptly provide to all the organs of nutrition, which enters the cells and to carry out timely decomposition products formed during metabolism.
The benefits of four-chamber heart
Fish have a two chamber heart, reptiles is three-chambered. Only mammals and birds have a heart with four chambers. The only exception in the environment of the reptiles is the crocodile. His heart called conditionally four, as his atrium are interconnected, and venous and arterial blood is sometimes mixed. Reptiles it is necessary for the active production of gastric juice and digesting large prey.
Scientists believe that the first four-chamber organ came from the dinosaurs and in the course of evolution preserved in their descendants.
- The structure of the heart allows the body not to depend on the ambient temperature. Warm-blooded creatures can be active even in the cold season without falling into suspended animation, like reptiles.
- Evolved heart allows you to evolve with others, creating favorable conditions for it.
To shrink muscle tissue of this organ begins at an early stage of embryonic development, and it happens regardless of external stimuli. This feature is called automaticity of the heart, and provides its specific neuromuscular structure that creates electrical impulses.
Cardiac cycle consists of three phases, characterized by alternate contraction and relaxation of different parts of the heart. The total duration of the relaxation of the heart muscle exceeds the period of its work, therefore the heart is working smoothly and never gets tired.