Heart in birds: structure and features of the circulatory system

Birds are a unique group of home-home organisms, whose lifestyle is associated with such a capability as flight. It is possible under the condition of hard work of the muscles of the sternum and the forelimbs - the wings. This process, in turn, is ensured by the continuous supply of myocytes with oxygen and nutrients, especially glucose.

Blood is a substance that carries them throughout the body, and its movement depends on the intense activity of the heart - the pump, which is tirelessly pumping liquid connective tissue. The transfer of oxyhemoglobin and organic substances is carried out by the circulatory system of birds. The heart is the main organ that provides blood circulation. Features of its structure and functions will be considered in this article.

Features of the circulatory system

Intensive metabolism in birds is possible for two reasons. The first is high blood pressure, which causes a high blood flow velocity in arteries and even veins. The second is the specificity of the blood supply to the lungs. The heart of the feathered four-chambered, left and right parts of it are not communicating (there is a full septum), so the blood does not mix: the left part is moving the arterial, and the right - the venous. On the metabolism of birds affects such a factor as passing through the kidneys not only arterial (as in mammals), but also venous blood through the portal system of blood vessels, therefore in liquid metabolites they have uric acid instead of urea. Next: blood cells - red blood cells - have representatives of Aves class nuclei, which increases the lifespan of these cells. From the left ventricle of the heart leaves the largest arterial vessel - the aorta. It has a right arc, the bifurcation of which leads to the formation of left and right nameless arteries, which provide the head and wings of birds with nutrients and oxygen.

Anatomy of the heart

Being a hollow muscular organ, it is located on the right side of the thorax and is covered with a pericardium - a pericardial sac. In front of the sternum, the heart of the birds is partially covered by additional respiratory organs - air sacs. It has the form of a cone, the tip of which occupies an intermediate position between the stomach and the liver.

Depending on the biological species of the bird, the shape of the heart can be different: from the round to the ellipsoid-elongated. This organ of circulation consists of three membranes: external - serous (epicardium), middle (myocardium) and internal (endocardium). The most important of them is the middle shell, on the structure of which high activity and heart efficiency depend.

Myocardium

It is formed by striated muscular tissue of a special structure, which distinguishes the heart from birds from all other internal organs containing only smooth muscles. The internal arrangement of cardiomyocytes provides strength and evenly distributes the load during their contraction. Another important feature of the cardiac muscle is the independence of the systole and diastole of the chambers: the atria and the ventricles. The cells of the myocardium are intertwined, therefore the nerve impulses lightly irradiate over the cardiomyocytes, and the entire membrane is instantaneously contracted.

Chambers of the heart

Two auricles - left and right, as well as two ventricles have several features related to the anatomy of the myocardium. Its wall is much stronger and thicker in the left half of the heart, since arterial blood is thrown out of its ventricle under great pressure into the aorta and then enters a large circle of circulation. In the heart, blood always moves in one direction: from the atria to the ventricles and then from the right into the pulmonary arteries, and from the left into the right arch of the aorta. At the border between the chambers are located atrioventralny valves, consisting of connective tissue: muscular and membranous. They do not allow a portion of blood to return from the ventricle to the atrium. The heart of a bird, the structure of its chambers and valves depends on which systematic group it belongs to.

In the newbies (real birds), the front left and right, as well as the posterior veins, flow into the right atrium independently, while in the olden hollow veins merge, forming a sine. Between him and the right atrium are formed two muscular valves. The first group includes birds of the family of blue-tailed, anseriformes, passerines, woodpeckers, etc. The second group consists of casuaro-like, kiwi-like, nanduiform, also called rattleless birds (non-flying).

Circles of blood circulation

As we have already mentioned, the heart of birds is four-chambered. Its structure determines two circles of blood circulation. A small circle (pulmonary) begins in the right ventricle, and ends in the left atrium. A large circle originates in the left ventricle. From the right arch of the aorta arteries branch and bring oxygen and nutrients to the cells of all the organs and tissues of the bird. The venous blood collects into the hollow veins that enter the right atrium, this ends the large circle of blood circulation.

Specificity of cardiac activity

Studying the main part of the circulatory system - the heart of the bird, the structure and functions of its chambers - we note that this organ has a sufficiently large value and mass with respect to the body weight. For example, in birds such as bullfinches, crows, ducks, about 1 - 1.3% of body weight, and in species with high speed and maneuverability of flight - up to 2%.

For example, in predatory birds - eagles-white-tailed, falcon - the heart index is about 1.8%. In addition, birds have high blood pressure, and the heart rate ranges from 200 to 600 beats per minute, and during the flight reaches 1200 heart beats.

In this paper, we answered the question, what kind of heart the birds have, having studied the features of the myocardium and characterizing the specificity of their cardiovascular activity.