For all, without exception, multicellular organisms with differentiated tissues and organs, the main condition for their life is the need to transfer oxygen and nutrients to the cells that make up their body. The transport function of the above compounds is performed by blood moving through a system of tubular elastic structures - vessels united in the circulatory system. Its evolutionary development, structure and functions will be considered in this paper.
Annelled worms
The circulatory system of organs first appeared in representatives of the type of annelids (annelids), one of which is the well-known earthworm - an inhabitant of the soil, increasing its fertility and belonging to the class of oligochaetes.
Since this organism is not highly organized, the circulatory system of the earthworm's organs is represented by only two vessels - dorsal and abdominal, connected by ring tubes.
Features of blood movement in invertebrate animals - molluscs
The circulatory system of organs in molluscs has a number of specificsigns: a heart appears, consisting of ventricles and two atria and distilling blood throughout the body of the animal. It flows not only through the vessels, but also in the spaces between the organs.
Such a circulatory system is called open. We observe a similar structure in representatives of the arthropod type: crustaceans, spiders and insects. Their circulatory system of organs is open, the heart is located on the dorsal side of the body and looks like a tube with partitions and valves.
The lancelet is the ancestral form of vertebrates
The circulatory system of animal organs with an axial skeleton in the form of a chord or spine is always closed. The cephalochordates, to which the lancelet belongs, have one circle of blood circulation, and the role of the heart is performed by the abdominal aorta. It is her pulsation that ensures blood circulation throughout the body.
Circulation in fish
The superclass fish includes two groups of aquatic organisms: the class cartilaginous and the class bony fish. With significant differences in the external and internal structure, they have a common feature - the circulatory system of organs, the functions of which are to transport nutrients and oxygen. It is characterized by the presence of one circle of blood circulation and a two-chambered heart.
The heart of fish is always two-chambered and consists of an atrium and a ventricle. Valves are located between them, so the movement of blood in the heart is alwaysunidirectional: from the atrium to the ventricle.
Circulation in the first land animals
These include representatives of the class of amphibians, or amphibians: moor frog, tree frog, spotted salamander, newt and others. In the structure of their circulatory system, complications of organization are clearly visible: the so-called biological aromorphoses. This is a three-chambered heart (two atria and a ventricle), as well as two circles of blood circulation. Both originate from the ventricle.
In a small circle, blood rich in carbon dioxide moves to the skin and sac-like lungs. Here gas exchange occurs, and arterial blood returns from the lungs to the left atrium. Venous blood from the vessels of the skin enters the right atrium, then in the ventricle, arterial and venous blood are mixed, and such mixed blood moves to all organs of the body of amphibians. Therefore, the level of metabolism in them, like in fish, is quite low, which leads to the dependence of the body temperature of amphibians on the environment. Such organisms are called cold-blooded or poikilothermic.
The circulatory system of reptiles
Continuing to consider the features of blood circulation in animals leading a terrestrial way of life, let us dwell on the anatomical structure of reptiles, or reptiles. Their circulatory system is more complex than that of amphibians. Animals belonging to the class of reptiles have a three-chambered heart: two atria and a ventricle, in which there is a small septum. Animals belonging to the ordercrocodiles have a solid partition in the heart, which makes it four-chambered.
And the reptiles that are part of the squamous order (monitor lizard, gecko, steppe viper, quick lizard) and related to the turtle order have a three-chambered heart with an open septum, as a result of which arterial blood flows to their forelimbs and head, and to tail and trunk - mixed. In crocodiles, arterial and venous blood does not mix in the heart, but outside it - as a result of the fusion of two aortic arches, therefore, mixed blood enters all parts of the body. Without exception, all reptiles are also cold-blooded animals.
Birds are the first warm-blooded organisms
The circulatory system of organs in birds continues to become more complex and improved. Their heart is completely four-chambered. Moreover, in the two circulations, arterial blood never mixes with venous blood. Therefore, the metabolism of birds is extremely intense: the body temperature reaches 40-42 ° C, and the heart rate ranges from 140 to 500 beats per minute, depending on the size of the bird's body. The pulmonary circulation, called the pulmonary circulation, supplies venous blood from the right ventricle to the lungs, then from them arterial blood, rich in oxygen, enters the left atrium. The systemic circulation begins from the left ventricle, then blood enters the dorsal aorta, and from it through the arteries to all organs of the bird.
The movement of blood through the vessels in mammals
Like the birdsMammals are either warm-blooded or homeothermic. In modern fauna, they hold the first place in terms of the level of adaptation and prevalence in nature, which is explained primarily by the independence of their body temperature from the environment. The circulatory system of mammals, whose central organ is a four-chambered heart, is an ideally organized system of vessels: arteries, veins and capillaries. Blood circulation is carried out in two circles of blood circulation. The blood in the heart never mixes: on the left side, the arterial moves, and on the right, the venous.
Thus, the circulatory system of organs in placental mammals provides and maintains the constancy of the internal environment of the body, that is, homeostasis.
The circulatory system of human organs
Due to the fact that man belongs to the class of mammals, the general plan of the anatomical structure and functions of this physiological system in him and animals is quite similar. Although bipedalism and the specific structural features of the human body associated with it still left a certain imprint on the mechanisms of blood circulation.
The circulatory system of the human organs consists of a four-chambered heart and two circles of blood circulation: small and large, which were discovered in the 17th century by the English scientist William Harvey. Of particular importance is the blood supply to human organs such as the brain, kidneys and liver.
The vertical position of the body andblood supply to the pelvic organs
Man is the only creature in the class of mammals whose internal organs press with their weight not on the abdominal wall, but on the girdle of the lower extremities, consisting of flat pelvic bones. The circulatory system of the pelvic organs is represented by a system of arteries coming from the common iliac artery. This is primarily the internal iliac artery, which brings oxygen and nutrients to the pelvic organs: the rectum, bladder, genitals, prostate in men. After gas exchange occurs in the cells of these organs and the arterial blood turns into venous blood, the vessels - the iliac veins - flow into the inferior vena cava, which carries blood to the right atrium, where the systemic circulation ends.
It should also be taken into account that all the organs of the small pelvis are rather large formations, and they are located in a relatively small volume of the body cavity, which often causes squeezing of the blood vessels that feed these organs. It usually occurs as a result of prolonged sedentary work, in which the blood supply to the rectum, bladder and other parts of the body is disturbed. This leads to congestion, provoking infection and inflammation in them.
Blood supply of the human genital organs
Ensuring the normal flow of reactions of plastic and energy metabolism at all levels of organization of our body, from the molecular to the organism, is performed by the circulatory system of human organs. The pelvic organs, which include the genitals,blood supply, as mentioned above, from the descending part of the aorta, from which the abdominal branch departs. The circulatory system of the genital organs is formed by a system of vessels that provide nutrients, oxygen and the removal of carbon dioxide, as well as other metabolic products.
Male gonads - the testicles, in which spermatozoa mature - receive arterial blood from the testicular arteries extending from the abdominal aorta, and the outflow of venous blood is carried out by the testicular veins, one of which - the left one - merges with the left renal vein, and the right one enters directly into the inferior vena cava. The penis is supplied with blood vessels from the internal pudendal artery: these are the urethral, dorsal, bulbous and deep arteries. The movement of venous blood from the tissues of the penis is provided by the largest vessel - the deep dorsalis vein, from which blood moves to the urogenital venous plexus associated with the inferior vena cava.
The blood supply to the female genital organs is carried out by the system of arteries. Thus, the perineum receives blood from the internal pudendal artery, the uterus is supplied by a branch of the iliac artery, called the uterine, and the ovaries are supplied with blood from the abdominal aorta. In contrast to the male reproductive system, the female reproductive system has a very developed venous network of vessels interconnected by bridges - anastomoses. Venous blood flows into the ovarian veins, which enter the inferior vena cava, which then flows into the right atrium.
In this article, we examined in detail the development of the circulatory system of animal and human organs, which provides the body withoxygen and nutrients necessary for life support.
