Circulatory systems in animals (closed and open). Which animals have an open circulatory system? What animals have a closed circulatory system?
It is from the biology course that we remember about the closed and open circulatory system. But it is to her that living beings owe the coordinated movement of blood throughout the body, which thereby ensures full functioning. The delivery of heat and nutrients to all organs of the human body, without which existence is impossible, is also a merit of normally circulating blood. Without it, there would be no metabolic processes affecting the metabolic rate.
Unclosed circulatory system
This type of blood circulation is characteristic of protozoa invertebrates, echinoderms, arthropods and brachiopods, as well as hemichordates.
They deliver oxygen and vital elements using diffuse currents. Some living beings develop pathways for blood to pass through. This is exactly how vessels with a rather primitive appearance arise, interrupted by slit-like spaces, which are called sinuses or lacunae.
A distinctive feature of an open circulatory system is that the speed of movement is too low in relation to the large volume of blood. It moves slowly, under low pressure, between the tissues, and then through the open ends of the venous vessels again gathers to the heart. Slow circulation of hemolymph leads to passive breathing and poor oxygen supply to the body.
In arthropods, the open circulatory system is designed to transport nutrients to the organs, as well as remove waste products. Blood movement is ensured by contractions of the heart, which is located in the posterior part of the aorta (dorsal vessel). It, in turn, branches into arteries, the blood from which flows into the washed internal organs and open cavities. This blood flow system is believed to be imperfect, unlike that of mammals and birds.
Closed circulatory system
This type of blood flow can consist of one or two circles - large and small. Circulating through them, the blood can periodically change its composition and become either venous or arterial.
In this system, metabolism passes only through the vascular walls, and the blood enclosed in them does not come into contact with the tissues of the body. This type is characteristic of humans, other vertebrates, some other groups of animals and annelids. In the former, blood flow occurs thanks to a well-developed muscular heart. Its contractions are carried out automatically, but it can also be regulated by the central nervous system.
Advantages of a closed blood system
This type is characterized by fairly high blood pressure. Unlike an open circulatory system, the speed of blood movement through the vessels is much faster here. At the same time, the time of one revolution is different for all organisms - for some it is twenty minutes, while for others the blood makes a revolution in sixteen seconds.
There are several factors that promote blood circulation throughout the body. These include the pressure present in the vessels and the difference between them, movements made during breathing, and contractions of the skeletal muscles.
Pulse
It is one of the main characteristics of the heart. With this phenomenon, the periodic dilation of the arteries coincides with the contraction of the heart muscle. The pulse rate depends on a large number of reasons: emotional and physical stress, body temperature, excess kilograms. According to generally accepted standards, the pulsation frequency of an adult should not exceed eighty beats per minute.
If any deviations are revealed during the measurement, this is a reason to think about the presence of heart disease and pay a visit to a specialist. And the opinion of incompetent relatives and neighbors in this case must be ignored.
The circulatory system (open and closed) is the mechanism that makes it possible to carry out the coordinated movement of blood (hemolymph) throughout the body, which ensures its full functioning. Its very movement in the system occurs in connection with pulsation or contractions of the thickened walls of the aorta and arteries, or the organs of movement and muscles of the body. It is with the help of blood circulation that substances and heat are transported for metabolic processes, which also affect the metabolic rate. Closed and open circulatory system: how do they differ and for whom are they characteristic? The answers to these questions will be presented in the article.
An open circulatory system is found in almost all invertebrates, as well as in lower chordates (lancelet). Blood flow in these organisms is determined by the contraction of the heart or “hearts” and also, to some extent, by the contraction of the body musculature. A characteristic feature is a large volume of blood at a low speed of its movement.
A closed circulatory system can consist of one (fish and cyclostomes) and two - small and large (reptiles, amphibians, birds, mammals). Flowing through the small and large circles, the blood periodically changes its composition, and is either venous or arterial. And in cold-blooded animals, venous and arterial blood even mix in the aorta or heart, while the blood flow speed is low. The exchange of substances between body tissues and blood occurs through the thin walls of capillaries. Filtration of breakdown products occurs mainly in the kidneys, or in other
The open circulatory system is very imperfect, but among those with a closed circulatory system, the most ideal option is found in birds and mammals. In representatives of these classes, it consists of a four-chambered heart and two circulation circles. Normally, it never mixes with the venous one. Quite high blood pressure is typical. Another advantage is the considerable speed of blood flow through the vessels (for comparison: the time of one blood turnover in insects is approximately 22 minutes, in a dog it is already 16 seconds, and in a rabbit it is 7.5 seconds). It is thanks to these features that higher species of animals are warm-blooded, which allows them to have a constant body temperature, regardless of environmental conditions. High metabolic efficiency is also characteristic of birds and mammals.
Blood circulation in the human body is ensured by the contractions of the heart, which works like a pump. Other factors that contribute to the movement of blood include respiratory movements and reductions in pressure differences in blood vessels. One of the characteristics of cardiac activity is pulse rate. The pulse is a periodic expansion of the arteries, which coincides with the contractions of the heart muscle. Its frequency depends on many reasons, including body weight, temperature and condition of the body, physical and emotional stress, etc. Normally in an adult it is 60-80 beats per minute. The speed of blood flow in the vessels varies: from less than 1 mm/s in capillaries to 50 cm/s in large arteries. The time of the entire blood circulation throughout the body is about 20-25 seconds. Blood moves in the direction of decreasing pressure, which is greatest in the aorta and large arteries and least, even negative, in the vena cava. The reverse movement of blood is also prevented by the valves that close the atrioventricular orifices, the mouths of the pulmonary artery and aorta, and the valves located on the walls of large veins. With sufficient contractility, blood circulation is not impaired.
As you can see, the open and closed circulatory system have very characteristic features, which every erudite person, and not only others, must know.
CIRCULATORY SYSTEM, a set of organs and structures of animals and humans involved in blood circulation. During evolution, the circulatory system was formed (independently in different groups of animals) from slit-like cavities in the parenchyma, which filled the primary body cavity in lower multicellular animals (for example, flatworms). There are open and closed circulatory systems. The first is formed by various vessels, which are interrupted by cavities without their own walls - lacunae or sinuses; in this case, the blood, called in this case hemolymph, comes into direct contact with all tissues of the body (including brachiopods, echinoderms, hemichordate arthropods, tunicates). In a closed circulatory system, blood circulates in vessels with their own walls.
In primitive worms, blood movement is ensured by contractions of the muscles of the body wall (the so-called musculocutaneous sac); in other groups, pulsating areas (“hearts”) are differentiated in various vessels equipped with muscular walls. On the basis of one of these areas, in the most highly organized animals, a special pulsating organ is formed - the heart. In different groups of invertebrates it develops on the dorsal side of the body, in vertebrates - on the ventral side. The blood vessels that carry blood from the heart are called arteries, and the blood vessels that carry blood to the heart are called veins. In a closed circulatory system, large arteries are successively divided into smaller and smaller ones, down to thin arterioles, which break up into capillaries, forming an extensive network in various tissues. From it, blood flows into thin venules; connecting with each other, they gradually form larger veins. Blood is called arterial if it is enriched with O 2 in the respiratory organs, and depleted in oxygen after passing through the capillary networks of other organs - venous.
Nemerteans have the simplest type of closed circulatory system (2 or 3 longitudinal blood vessels connected to each other by jumpers). In many of them, blood circulation is not ordered: blood moves back and forth through the vessels when the muscles of the body contract. In the so-called hoplonemertines, the walls of blood vessels acquired contractility; blood flows forward through the median dorsal vessel, and backward through the two lateral vessels. In the closed circulatory system of annelids, the dorsal and abdominal longitudinal vessels are connected by vascular arches passing in the septa between the body segments. Arteries extend from them to the lateral appendages of the body (parapodia) and gills; blood movement is ensured by the pulsation of the walls of some vessels; Blood flows forward through the spinal vessel, and backward through the abdominal vessel.
Arthropods, brachiopods and mollusks develop a heart. During evolution, the circulatory system in arthropods loses its closedness: hemolymph from the arteries enters the system of lacunae and sinuses and returns to the heart through holes in its walls (ostia), equipped with valves that prevent its reverse movement. This is most pronounced in insects, which is associated with the increased development of their tracheal system, which transports O 2 and CO 2. In mollusks, all transitions from an open to an almost closed (cephalopod) circulatory system are observed, and the function of the heart increases; it has atria, into which in some groups veins flow, collecting hemolymph from the peripheral sinuses. In cephalopods, a circulatory system is formed, including capillary networks, and the heart is supplemented by pulsating vessels at the bases of the gills (the so-called gill hearts).
The circulatory system reaches significant perfection during the evolution of chordates. In skullless animals (lancelets), the role of the heart is played by a pulsating longitudinal vessel passing under the pharynx - the abdominal aorta. Branchial arteries depart from it, located in the partitions between the gill slits. Blood enriched with O2 enters the dorsal aorta and the arteries extending from it to various organs. To the head end of the body, blood flows from the anterior branchial arteries through the carotid arteries. From the capillary networks, blood collects into veins, the most important of which are longitudinal paired anterior (from the head end of the body) and posterior (from the area behind the pharynx) cardinal veins, flowing into the Cuvier ducts (through them blood enters the abdominal aorta). The hepatic vein also flows there, carrying blood from the capillary network of the portal system of the liver. In vertebrates, the heart is formed from the posterior part of the abdominal aorta, which in cyclostomes and fish includes the sinus venosus, atrium, ventricle and conus arteriosus. In cyclostomes, the circulatory system is not yet closed: the gills are surrounded by circumbranchial sinuses. All other vertebrates have a closed circulatory system; it is supplemented by an open lymphatic system. In most fish, arterial blood from the gills enters the carotid arteries and dorsal aorta, and the heart receives venous blood from the capillary networks of the head and body organs.
Ancient lobe-finned fish developed additional respiratory organs - lungs, which allowed them to breathe atmospheric air with a deficiency of O 2 dissolved in water. An additional pulmonary (pulmonary) circulation appears: the lungs receive venous blood through the pulmonary arteries (arising from the posterior pair of branchial arteries) and return O2-saturated arterial blood through the pulmonary veins to the isolated left atrium. The left half of the heart becomes arterial, while the right still receives venous blood from the rest of the body. A system of internal partitions and valves is formed in the heart, distributing blood in such a way that arterial blood from the left atrium (from the lungs) enters mainly the carotid arteries and goes to the head (the brain is most sensitive to oxygen deficiency), and venous blood - from the right atrium to gills and lungs.
In terrestrial vertebrates, further rearrangements of the circulatory system occurred. The heart of amphibians is divided into the sinus venosus, which drains into the right atrium, left atrium, common ventricle and conus arteriosus. The loss of gills led to reduction of the abdominal aorta; The branchial arteries became part of the carotid arteries, aortic arches and pulmonary arteries, starting from the conus arteriosus. The aortic arches form the dorsal aorta. In the venous system, the posterior cardinal veins are reduced, functionally replaced by the azygos posterior vena cava. The anterior cardinal veins are called the superior (internal) jugular veins, and the ducts of Cuvier are called the anterior vena cava. In amphibians, an important additional respiratory organ is the skin, arterial blood from which passes through the vena cava into the venous sinus and then into the right atrium, and arterial blood from the lungs through the pulmonary veins into the left atrium. Arterial blood from both respiratory organs mixes with venous blood in the common ventricle of the heart.
In reptiles, with the improvement of the lung ventilation mechanism, the need for skin respiration has disappeared. In most of them, the venous sinus and conus arteriosus were reduced; the heart consists of two atria and a ventricle, in which there is an internal, usually incomplete (except in crocodiles) septum, which allows the flow of arterial and venous blood coming from the left and right atria to be partially separated and redistributed in accordance with physiological needs. Reptiles retain 2 aortic arches, from which the right one receives arterial blood, and the left one receives mixed blood; Venous blood enters the pulmonary artery.
In birds and mammals, complete division of the ventricle of the heart led to the formation of four chambers: the left and right atria and ventricles. The only surviving aortic arch (right in birds, left in mammals and humans) starts from the left ventricle, passes into the carotid and subclavian arteries and into the dorsal aorta. The common pulmonary artery begins from the right ventricle. The renal portal system, which was present in most primitive vertebrates (except cyclostomes), is reduced. All these changes in the circulatory system contributed to a significant increase in the overall level of metabolism of the body in birds and mammals.
Lit.: Tatarinov L.P. Evolution of the apparatus for separating blood currents in the heart of vertebrates // Zoological Journal. 1960. T. 39. Issue. 8; Beklemishev V.N. Fundamentals of comparative anatomy of invertebrates. 3rd ed. M., 1964. T. 2; Romer A., Parsons T. Anatomy of vertebrates. M., 1992. T. 2.
is an area of necessary knowledge related to health.
A person is 60% liquid. It is found in all organs, even in those that at first glance seem dry - nail plates and. Neither, nor, nor even are possible without the participation of lymph and tissue fluid.
Circulatory system
Blood circulation is an important factor in the life of the human body and a number of animals. Blood can perform its various functions only by being in constant motion.
Blood circulation occurs along two main paths, called circles, connected in a sequential chain: the small and large circle of blood circulation.
In a small circle, blood circulates through the lungs: from the right ventricle it enters the lungs, where it is saturated with oxygen and returns to the left atrium.
The blood then enters the left ventricle and is sent through the systemic circulation to all organs of the body. From there, the blood carries carbon dioxide and breakdown products through the veins to the right atrium.
Closed circulatory system
A closed circulatory system is a circulatory system in which veins, arteries and capillaries are present (in which the exchange of substances between blood and tissues occurs), and blood flows exclusively through the vessels.
The closed system differs from the open circulatory system by the presence of a well-developed four-chamber, three-chamber or two-chamber heart.
The movement of blood in a closed circulatory system is ensured by the constant contraction of the heart. Blood vessels in a closed circulatory system are located throughout the body. The unclosed one has only one open blood path.
Human circulatory system
Colorless, amoeba-like cells are called leukocytes. They are protectors because they fight harmful microorganisms. The smallest platelets of blood are called platelets.
Their main task is to prevent blood loss when blood vessels are damaged, so that any cut does not become a mortal threat to humans. Red blood cells, white blood cells and platelets are called the formed elements of blood.
Blood cells float in plasma - a light yellow liquid, which is 90% composed of. Plasma also contains proteins, various salts, enzymes, hormones and glucose.
Blood in our body moves through a system of large and small vessels. The total length of blood vessels in the human body is approximately 100,000 km.
Main organ of the circulatory system
The main organ of the human circulatory system is the heart. It consists of two atria and two ventricles. Arteries extend from the heart through which it pumps blood. Blood returns to the heart through the veins.
With the most minor injury, blood begins to flow from damaged vessels. Blood clotting is ensured by platelets. They accumulate at the site of injury and release a substance that helps thicken the blood and form a blood clot.
- To more accurately diagnose diseases, blood tests are done. One of them is clinical. It shows the quantity and quality of blood cells.
- Since blood enriched with oxygen moves through the arteries, the arterial membrane, unlike the venous one, is more powerful and has a muscular layer. This allows it to withstand high pressure.
- One drop of blood contains more than 250 million red blood cells, 375 thousand leukocytes and 16 million platelets.
- Contractions of the heart ensure the movement of blood through the vessels to all organs and tissues. At rest, the heart contracts 60-80 times per minute - this means that about 3 billion contractions occur over a lifetime.
Now you know everything an educated person should know about the human circulatory system. Of course, if your specialty is medicine, then you will be able to talk much more about this topic.
