During the fusion of veins in the highway, five systems of branches can be distinguished: 1) the cranial vena cava; 2) the caudal vena cava; 3) the portal vein of the liver; 4) pulmonary veins (small circle of blood circulation); 5) the circle of blood circulation of the heart itself.
The course of the veins of the systemic circulation in most cases corresponds to the course of the arteries running together in the neurovascular bundles, but also has a number of significant differences.
The veins of the trunk are mainly represented by the cranial and caudal vena cava and their branches.
Cranial vena cava - v. cava cranialis at the entrance to the chest cavity is formed: 1) the trunk of the jugular veins - truncus bijugularis, carrying blood from the head; 2) axillary (right and left) veins that carry blood from the chest limbs; 3) the cervical veins, which correspond to the arteries extending from the subclavian arteries (deep cervical, costo-cervical and vertebral). Further, the cranial vena cava passes in the cranial part of the mediastinum and receives blood from the internal thoracic veins, which collect it from the ventral part of the chest, and flows into the right atrium, forming the venous sinus. In a horse, this sinus also includes the right azygos vein, which collects blood from the intercostal veins. (The venous system that removes blood from the lungs is indicated when describing the pulmonary circulation).
Caudal vena cava - v. cava caudalis is formed by fusion in the area of the fifth to sixth lumbar vertebra of the paired common iliac and unpaired median-sacral veins. Takes place in abdominal cavity under the spinal column to the right of the aorta to the diaphragm, then descends between the diaphragm and the blunt edge of the liver to the opening of the vena cava, located in the tendon center, the diaphragm, and enters chest cavity, where it follows in the mediastinum ventrally from the esophagus and flows at the level of the coronary sulcus into the right atrium. Along the way, the caudal vena cava receives blood from the kidneys (paired renal veins), gonads (paired ovarian or testicular veins) and the abdominal walls. The short trunk of the portal vein is formed by the fusion of the gastro-splenic, cranial and caudal mesenteric veins, goes to the right and enters the gate of the liver, where it is divided into interlobular veins, and then into the capillaries of the hepatic lobules. Inside each lobule, capillaries flow into the central vein of the lobule. These are the initial sections of the veins that drain blood from the liver into the caudal vena cava. Thanks to such a wonderful venous network, the blood flowing from the gastrointestinal tract is rendered harmless from toxins and other harmful substances.
In newborn animals up to 12-16 days of age, and in calves of industrial complexes up to 30 days of age, the ductus venosus, which extends from the umbilical vein (before entering the liver) and flows into the caudal vena cava, does not obliterate the ductus venosus. Through this duct in the fetus and in the first days of life in the newborn, the blood passes in transit into the caudal vena cava, without getting into the wonderful venous network of the liver and, thus, without going through filtration. Apparently, this is due to the fact that with colostrum or mother's milk at this time, the immune bodies necessary to protect the body arrive, which, bypassing the liver barrier, go into the blood of a calf that is born sterile and does not have its own defense system until the age of 14 days. In a newborn, albumin and globulins of colostrum or milk easily penetrate through the intestinal wall into the blood and immediately pass from the portal vein along the venous duct, bypassing the liver barrier, into the general bloodstream, providing protection for the body.
Paired renal veins flow into the caudal vena cava, which are very short large trunks that emerge from the hilum of the kidney. Near the renal veins, there are small trunks of the adrenal veins that drain into the caudal vena cava. From the ovaries comes the ovarian vein - v. ovarica, from testes - testes - v. testiculars. Deoxygenated blood from them is diverted directly into the caudal vena cava. Venous blood from the abdominal wall and lower back into the caudal vena cava flows through the segmental paired lumbar veins - vv. lunibales.
Venous outflow from the udder. Special attention in lactating cows, venous outflow from the udder deserves, which occurs in both vena cava - caudal and cranial. In the cranial direction, the udder veins - w. uberi are collected in the caudal epigastric superficial (milk) vein - v. epigastrica caudalis superficialis, which goes under the skin along the ventral abdominal wall to the area of the xiphoid cartilage in the form of a tortuous cord. At this point, it pierces the wall, forming a significant hole called the "milk well" and flows into the internal thoracic vein - v. thoracica interna, which is directed along the inner surface of the costal cartilage into the cranial vena cava. The milk vein is clearly visible and palpable together with the "milk well", which is used in veterinary practice.
From the tail, blood flows through the tail veins - w. caudales, which then continue as sacral lateral veins - w. sacrales laterales. Along the tail are paired dorsal and ventral tail veins and one (larger) unpaired tail vein, which runs under the bodies of the caudal vertebrae (in veterinary practice, it is used for intravenous injections).
In mammals, as in birds, the large and small circles of blood circulation are completely separated. One left aortic arch departs from the left ventricle of the four-chambered heart. In most species, a short, unnamed artery is separated from it, dividing into the right subclavian and carotid (right and left) arteries; left subclavian artery departs on its own. The dorsal aorta - a continuation of the left arch - branches off the vessels to the muscles and internal organs (Fig. 99).
Only a few mammals have both anterior vena cava equally developed; in most species, the right anterior vena cava accepts the unnamed vein formed by the confluent veins. jugular and left subclavian veins. The rudiments of the posterior cardinal veins of the lower vertebrates are also asymmetrical - the so-called unpaired (vertebral) veins, characteristic only of mammals. In most species, the left azygos vein (v. Hemiazygos) is connected to the right azygos vein (v. Azygos), which flows into the right anterior vena cava. The absence of the portal system of the kidneys is characteristic, which is associated with the peculiarities of the excretory processes,
Valved lymphatic vessels open into venous vessels near the heart. They begin with lymphatic capillaries that collect interstitial fluid (lymph). V lymphatic system mammals lack lymphatic hearts (pulsating areas of blood vessels), but there are lymph nodes (glands), the function of which is to cleanse the lymph from pathogens with the help of phagocytic cells - lymphocytes (Fig. 100). By chemical composition lymph is similar to blood plasma, but poorer in proteins. In the lymphatic vessels in contact with the digestive tract, the lymph is enriched with fats, the molecules of which cannot penetrate the dense walls of the capillaries blood vessels but easily pass through more permeable walls lymphatic vessels... Form elements of lymph are different types lymphocytes (white blood cells).
The hematopoietic organs are specialized. Bone marrow produces red blood cells, granulocytes and platelets; spleen and lymph glands - lymphocytes; reticuloendothelial system - monocytes.
Substances agglutinins, lysines, precipitins and antitoxins neutralize or destroy harmful substances caught in the blood. They have a high degree of specificity. Small erythrocytes of mammals do not have nuclei, which increases the efficiency of oxygen transfer by them, since they consume oxygen 9-13 times less than erythrocytes of birds for their own respiration and 17-19 times less than erythrocytes of amphibians. The amount of blood in mammals is close to that of birds. The relative size of the heart is greater in more mobile and small animals. Have large species the weight of the heart is 0.2-0.7% of the body weight, in small ones - up to 1-1.5; in bats - 1.3% (
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 function of transport of the above compounds is performed by blood moving through the system of tubular elastic structures - vessels, united into the circulatory system. Its evolutionary development, structure and functions will be considered in this work.
Ringed worms
Circulatory system organs first appeared in representatives of the ring type, one of which is the well-known earthworm - an inhabitant of the soil, increasing its fertility and belonging to the class of small bristles.
Since this organism is not highly organized, the circulatory system of the earthworm organs is represented by only two vessels - the dorsal and abdominal, connected by annular tubes.
Features of the movement of blood in invertebrates - mollusks
The circulatory system of organs in molluscs has a number of specific features: 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 gaps 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 septa and valves.
Lancelet - an ancestral form of vertebrates
The circulatory system of animal organs with an axial skeleton in the form of a notochord or spine is always closed. In the cephalochordates, to which the lancelet belongs, one circle of blood circulation, and the role of the heart is played by the abdominal aorta. It is its pulsation that ensures blood circulation throughout the body.
Blood circulation in fish
The fish superclass includes two groups aquatic organisms: class cartilaginous and class bony fish. With significant differences in external and internal structure they have 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 in 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 always unidirectional: from the atrium to the ventricle.
Blood circulation in the first land animals
These include representatives of the class of amphibians, or amphibians: 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. These are (two atria and a ventricle), as well as two circles of blood circulation. Both of them start from the ventricle.
In a small circle, blood rich in carbon dioxide moves to the skin and sac-like lungs. Here gas exchange takes place, and returns from the lungs to the left atrium. Venous blood from the vessels of the skin enters the right atrium, then arterial and venous blood mix in the ventricle, and such mixed blood moves to all organs of the amphibians' body. Therefore, the level of metabolism in them, like in fish, is rather 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 in 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. The circulatory system of their organs is more complex than that of amphibians. Animals belonging to the class of reptiles have a three-chambered heart: two atria and a ventricle, which has a small septum. Animals belonging to the order of crocodiles have a solid partition in the heart, which makes it four-chambered.
And the reptiles included in the squamous squad (monitor lizard, gecko, steppe viper, and those belonging to the tortoise squad) have a three-chambered heart with an open septum, as a result of which arterial blood flows to their forelimbs and head, and mixed blood to the tail and trunk sections. In crocodiles, arterial and venous blood is mixed not in the heart, but outside it - as a result of the fusion of two aortic arches, therefore mixed blood flows to all parts of the body.All reptiles, without exception, are also cold-blooded animals.
Birds are the first warm-blooded organisms
The circulatory system of organs in birds continues to grow in complexity and improve. Their heart is completely four-chambered. Moreover, in two circles of blood circulation, 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 small circle of blood circulation, called the pulmonary, 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 the blood enters the dorsal aorta, and from it through the arteries to all organs of the bird.
in mammals
Like birds, mammals belong to warm-blooded or the environment... The circulatory system of mammals, the central organ of which is the 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. Blood in the heart never mixes: arterial blood moves in the left side, and venous in the right.
Thus, the circulatory system of organs in placental mammals provides and maintains constancy internal environment organism, that is, homeostasis.
The circulatory system of human organs
Due to the fact that man belongs to the class of mammals, overall plan anatomical structure and the functions of this physiological system he and animals are quite similar. Although bipedal locomotion and associated specific features the structure of the human body still left a certain imprint on the mechanisms of blood circulation.
The circulatory system of 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 such human organs as the brain, kidneys and liver.
Vertical position of the body and blood supply to the pelvic organs
Man is the only creature in the mammalian class whose internal organs do not put pressure on abdominal wall, and on the belt lower limbs 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: rectum, bladder, genitals, prostate in men. After gas exchange occurs in the cells of these organs and arterial blood turns into venous, the vessels - the iliac veins - flow into the inferior vena cava, which carries blood to the right atrium, where it ends big circle blood circulation.
It should also be borne in mind that all the pelvic organs are rather large formations, and they are located in a relatively small volume of the body cavity, which often causes the 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 is disturbed, Bladder and other parts of the body. This leads to congestion, provoking infection and inflammation in them.
Blood supply to the human genital organs
Security normal flow reactions of plastic and energy metabolism at all levels of the organization of our body, from molecular to organismic, are carried out by the circulatory system of human organs. The organs of the small pelvis, which include the genitals, are supplied with blood, 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 the supply of nutrients, oxygen and the removal of carbon dioxide, as well as other metabolic products.
The male sex glands - the testicles in which the sperm 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 - merges with the left renal vein, and the right one enters directly into the lower vena cava. The penis is supplied with blood vessels extending from the internal genital artery: this is the urethral, dorsal, bulbous and deep arteries. The movement of venous blood from the tissues of the penis provides largest vessel- deep dorsal vein, from which blood flows to the genitourinary venous plexus associated with the inferior vena cava.
The blood supply to the female genital organs is carried out by the artery system. Thus, the perineum receives blood from the internal genital artery, the uterus is supplied with blood by a branch of the iliac artery called the uterine artery, 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 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 with oxygen and nutrients essential for life support.
After the birth of the fetus, with its first breath, the placental circulation is turned off and fundamental changes occur in the circulation, as a result of which a definitive, or constant, blood circulation is established, typical for an adult animal (Fig. 64).
These changes boil down to the following. Expands upon inhalation rib cage, and with it the lungs; due to this, blood from the pulmonary artery no longer rushes into the ductus arteriosus, but is sucked into the capillary network of the lungs (9). From the lungs, blood is directed through the pulmonary veins (8) to the left atrium (7), where, therefore, blood pressure, whereby the oval hole in atrial septum it is closed by the valve in it, which soon grows to the edges of the hole on the left side; thus, both atria are disconnected.
After a short time, the ductus arteriosus also overgrows, turning into an arterial ligament-ligamentum arteriosum (6). With the shutdown of the ductus arteriosus, the blood pressure in the branches extending from the aorta is leveled and all parts of the body receive blood under the same initial pressure.
When the placenta is turned off, the umbilical arteries and veins are desolate, and the umbilical arteries, obliterating, turn into round ligaments of the bladder, and the unpaired (by the time of birth) umbilical vein - into a round ligament of the liver.
From the ductus venosus in a dog and cattle the venous ligament-lig.venosum-connecting the portal vein with the caudal vena cava remains on the liver. Ultimately, these ligaments also undergo a strong reduction, until they disappear completely.
As a result of the described changes that occur after birth, two circles of blood circulation are established in adult animals.
In the small, or respiratory, circulation, venous blood from the right ventricle is carried out by the pulmonary artery into the capillaries of the lungs, where it undergoes oxidation (17, 5, 9). Arterial blood from the lungs through the pulmonary veins returns again to heart-to the left the atrium - and from there it enters the corresponding ventricle (8, 7,18).
In the large, or systemic, circulation, blood from the left ventricle of the heart is pushed into the aorta and carried by its branches through the capillaries of the whole body (18,10,15), where it loses oxygen, nutrients and is enriched with carbon dioxide and cellular waste products. From the capillaries of the body, venous blood is collected by two large vena cava - cranial and caudal - again into the heart, into the right atrium (2, 11, 16).
The radical changes in the blood circulation that occur after the birth of the fetus, of course, cannot but affect the development of the heart itself. The work of the heart during placental and postembryonic circulation is not the same, and hence there is a difference in the relative size of the heart. So, with placental circulation, the heart has to drive all the blood through the capillaries of the body and, in addition, through the capillaries of the placenta; after birth, the placental capillary system falls out, and the blood is distributed between the pulmonary and systemic circulation. Thus, the work of the right part of the heart decreases, and the left, on the contrary, increases, which entails for the first time a general decrease in the whole heart. So, in newborn primates, 7.6 g of heart weight per kilogram of body weight, after a month - already 5.1 g, after two months - 4.8 g, after four months - 3.8 g. Then the heart increases again, which , obviously, can be connected with the increased movements of the cub, which cause an increase in the load of the heart. This increase in weight continues until the 15th month, when the relative weight of the heart reaches 5 g per kilogram of body weight, maintaining this ratio (with fluctuations up to 6.13 g) throughout life. From the given digital data it can be seen that the size of the heart is closely related to its work. This is also proved experimentally.
The mammalian circulatory system is higher form blood circulation.
Like birds, it is characterized by a four-chambered heart and two circles - large and small.
This form contributes to expedited exchange substances in comparison with other groups of vertebrates: in fact, we have "two hearts" installed in different parts vascular system... The blood in both halves of the heart does not mix.
"Pulmonary" circle
The right half of the heart is "responsible" for the small circle. From the right ventricle, venous blood, depleted in oxygen, is directed along pulmonary arteries into the lungs. There it is saturated with oxygen and follows the pulmonary veins into the left atrium.
Oxygen saturation is more active in mammals with an active lifestyle, namely in predators; in sedentary animals, gas exchange is relatively slow.
The "main" circle of blood circulation
The large circle originates in the left ventricle. The only aortic arch extending from it is left, and not right, like in birds. Branches from it carry blood throughout the body, saturating organs and tissues with oxygen and other essential substances.
the structure of the circulatory system of mammals photo
From them she accepts carbon dioxide and metabolic products. Venous blood, saturated with carbon dioxide, is directed through the veins to the right atrium. Two hollow veins flow into it, the first of which carries blood from the head and forelimbs, and the second from the back of the body.
Mammalian blood composition
The blood of mammals consists of liquid plasma, which contains a full set of so-called shaped elements:
- Erythrocytes are carriers of the iron-containing substance of hemoglobin, they carry out the transfer of oxygen;
- Platelets are the bodies responsible for blood clotting and serotonin metabolism;
- Leukocytes - little bodies white responsible for immunity.
Erythrocytes and platelets of mammals, unlike other groups of animals, do not contain nuclei. Platelets are actually "platelets"; the absence of nuclei in erythrocytes is explained by the need to accommodate a larger amount of hemoglobin.
Also, erythrocytes do not have mitochondria, so they carry out the synthesis of ATP without using oxygen, which makes them the most effective carriers of it.
Lymphatic system
The lymphatic system is closely connected with the circulatory system and is an intermediary between it and tissues in the exchange of nutrients. It consists of blood plasma and lymphocytes.
It is noteworthy that mammals do not have "lymphatic hearts", unlike reptiles and amphibians - this is the name for the parts of the lymphatic vessels that can contract: the lymph in mammals leading a much more active lifestyle moves due to the contraction of the skeletal muscles.
Mammals also have lymph nodes that cleanse the lymph from harmful microorganisms. In its composition, lymph is similar to blood, but it contains less protein and more fat. Fats enter it from the digestive tract.
Pulse
The heart rate in mammals is high, but significantly lower than in birds. The exception is small animals like mice, whose heart rate is 600 beats. A dog has a pulse rate of 140 beats, while a bull and an elephant have only 24 beats. Aquatic mammals are able to lower their heart rate after diving.
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