A closed circulatory system has. What animals have an open circulatory system

Is an area of \u200b\u200bessential health-related knowledge.

A person is 60% liquid. It is found in all organs, even in those that at first glance seem to be dry - nail plates and. Neither, nor, not even 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 fulfill 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.

Then the blood enters the left ventricle and is sent through a large circle of blood circulation to all organs of the body. From there, through the veins, the blood carries carbon dioxide and decay products to the right atrium.

Closed circulatory system

A closed circulatory system is a circulatory system in which there are veins, arteries and capillaries (in which the exchange of substances between blood and tissues takes place), and blood flows exclusively through the vessels.

A closed system differs from an open circulatory system by the presence of a well-developed four-chambered, three-chambered or two-chambered heart.

The movement of blood in a closed circulatory system is provided by the constant contraction of the heart. Blood vessels in a closed circulatory system are found throughout the body. The unclosed one has only one unclosed blood pathway.

Human circulatory system

The colorless cells that look like amoebas are called leukocytes. They are defenders, as they fight harmful microorganisms. The smallest platelets of blood are called platelets.

Their main task is to prevent blood loss in case of damage to blood vessels, so that any cut does not become a mortal threat to a person. Erythrocytes, leukocytes and platelets are called blood cells.

Blood cells float in plasma, a light yellow liquid that is 90% composed of. Plasma also contains proteins, various salts, enzymes, hormones and glucose.

The blood in our body moves through the system of large and small vessels. The total length of blood vessels in the human body is approximately 100,000 km.

The 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 leave the heart, through which it pushes blood. The blood returns to the heart through the veins.

With the slightest injury, blood begins to flow from the damaged vessels. Blood clotting is provided by platelets. They accumulate at the site of injury and secrete a substance that helps blood thicken and form a blood clot (clot).

• For a more accurate diagnosis of 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, in contrast to the venous membrane, is more powerful and has a muscle layer. This allows her to withstand high pressure.
• One drop of blood contains more than 250 million erythrocytes, 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 beats 60-80 times per minute, which means that about 3 billion contractions occur in a lifetime.

Now you know everything that an educated person should know about the human circulatory system. Of course, if you specialize in medicine, then you can tell a lot more on this topic.

Even from the school course in biology, many remember that the circulatory system can be closed and open, but not everyone will remember the difference between them. It is thanks to the circulatory system that the coordinated movement of blood through the body is carried out, which by itself indicates the provision of full-fledged life. Without normal blood circulation, due to which all nutrients and heat are delivered to all organs of our body, a person would not be able to live a day. In addition, without blood circulation, there would be no metabolic processes that have an impact on the metabolic rate.

An open circulatory system is found in invertebrates, including the lancelet... This type of blood circulation has one distinctive feature, namely, compared with such a large volume of blood, the speed of its movement is too slow. As for the closed circulatory system, it can consist of either one or two circles - small and large. An interesting fact - circulating in a small and large circle, the blood can periodically change its composition and be either arterial or venous.

An open circulatory system is typical for arthropods, for example, mollusks, and for such a simple invertebrate as the lancelet. In these species, the delivery of useful and vital substances, including oxygen, is carried out from the place of their perception to parts of the body by means of diffuse currents. It also happens that in some animals there are paths along which blood passes - in fact, this is how the vessels appear, which have a rather primitive appearance.

Not everyone knows that evolutionary processes took place in the circulatory system, which, in one way or another, influenced its development. For the first time you could hear this back in school, from someone who taught you biology. For the first time, the circulatory system appeared in annelids - it has a vicious circle.

It should be noted that chordates and invertebrates have different theories of evolution, each of which has its own characteristics.

First, there was a significant increase in the transport function, which is the most important, due to the formation of the heart and large arteries. Secondly, the number of the so-called performed functions has expanded, which include thermoregulation and protective reactions. Thirdly, there have been changes in the change of habitat, lifestyle, as well as pulmonary respiration. Both closed and open circulatory systems have characteristic features that every person needs to know about, even in general terms.

Key Features

It is believed that the open circulatory system is somewhat imperfect, which cannot be said about birds and mammals, which have a closed circulatory system. In all representatives of this type, the system consists of a heart with four chambers and two circles of blood circulation, which are subdivided into small and large. Under normal conditions, the circulating blood in such a system never mixes with each other.

A closed circulatory system has the following advantages:

• Such a system is characterized by a fairly high pressure.
• The rate of blood circulation through the vessels. An interesting fact, the time it takes for one turn of blood is different for everyone, for example, for small bugs, passing one circle takes at least twenty minutes, and for a dog - sixteen seconds.

In the human body, blood circulates through the veins, blood vessels and arteries due to the contraction of the muscles of the heart, the work of which can be compared to a pump. Among other things, there are several other factors that contribute to the movement of blood through the body, which a person may not know about and hear about them for the first time in his life.

It is customary to refer to such factors:

• Movements performed during breathing.
• Contraction of skeletal muscles.
• The pressure in the vessels and the difference between them.

One of the main characteristics of the heart is pulse rate. What is it? Pulse is a phenomenon in which the arteries expand, moreover, it occurs periodically and coincides with the contraction of the heart muscle. The pulse rate can depend on many reasons, each person has its own. So, even extra pounds, temperature and stress, both physical and emotional, can affect the pulse. There are generally accepted norms, for example, in an adult, the pulse rate can range from sixty to eighty beats per minute.

If, when measuring the heart rate, some deviation was revealed, there is a reason to think about it and make an appointment with a specialist, as this may indicate the presence of any deviation. You should not listen to the opinion of relatives who do not have a medical education; the most ideal option would be to simply consult with your therapist about this.

BLOOD SYSTEM, a set of organs and structures of animals and humans involved in blood circulation. In the course of 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 organisms (for example, flatworms). Distinguish between open and closed circulatory system. The first is formed by various vessels, which are interrupted by cavities devoid of their own walls - lacunae or sinuses; at the same time, the blood, called in this case hemolymph, comes into direct contact with all tissues of the body (including brachiopods, echinoderms, arthropods, hemichordates, tunicates). In a closed circulatory system, blood circulates in vessels with their own walls.

In primitive worms, the movement of blood is provided by contractions of the musculature of the body wall (the so-called musculocutaneous sac); in other groups, pulsating sections ("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. The blood vessels that carry blood from the heart are called arteries, and those that carry blood to the heart are called veins. In a closed circulatory system, large arteries are sequentially divided into smaller and smaller ones, up to thin arterioles, which break up into capillaries, forming an extensive network in various tissues. From it, blood enters the 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, depleted in oxygen after passing through the capillary networks of other organs - venous.

The simplest type of closed circulatory system is possessed by nemertins (2 or 3 longitudinal blood vessels are connected to each other by bridges). In many of them, blood circulation is not ordered: blood moves forward and backward through the vessels when the muscles of the body contract. In the so-called hoplonemertins, the walls of the 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 branch off from them to the lateral appendages of the body (parapodia) and gills; the movement of blood is provided by the pulsation of the walls of some vessels; blood flows forward through the dorsal vessel, backward through the abdominal vessel.

Arthropods, brachiopods, and molluscs develop a heart. In the course of evolution, the circulatory system in arthropods loses its closure: the 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 enhanced development of the tracheal system in them, which transports O 2 and CO 2. In molluscs, all the transitions from an open to an almost closed (cephalopod) circulatory system are observed, the function of the heart is enhanced; it has atria, into which in some groups veins flow, collecting hemolymph from the peripheral sinuses. In cephalopods, a circulatory system is formed, which includes capillary networks, and the heart is supplemented with pulsating vessels at the bases of the gills (the so-called gill hearts).

The circulatory system achieves significant perfection during the evolution of chordates. In noncranial (lancelet), the role of the heart is played by a pulsating longitudinal vessel passing under the pharynx - the abdominal aorta. The branchial arteries, located in the septa between the branchial clefts, branch off from it. Blood enriched with O 2 enters the dorsal aorta and 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 is collected in the veins, the most important of which are the longitudinal paired anterior (from the head end of the body) and posterior (from the area behind the pharynx) cardinal veins that flow into the Cuvier ducts (through which blood enters the abdominal aorta). The hepatic vein also flows there, carrying out blood from the capillary network of the liver portal system. In vertebrates, the heart is formed from the posterior part of the abdominal aorta, which in cyclostomes and fish includes the venous sinus, atrium, ventricle, and arterial cone. In cyclostomes, the circulatory system is still open: the gills are surrounded by peri-tibial sinuses. All other vertebrates have a closed circulatory system; it is complemented 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.

The ancient cross-finned fish developed additional respiratory organs - lungs, which allow them to breathe atmospheric air with a deficiency of O 2 dissolved in water. An additional small (pulmonary) circle of blood circulation appears: the lungs receive venous blood through the pulmonary arteries (originated from the posterior pair of gill arteries) and return arterial blood saturated with O 2 through the pulmonary veins into the isolated left atrium. The left side of the heart becomes arterial, while the right side still receives venous blood from the rest of the body. In the heart, a system of internal partitions and valves is formed that distribute 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 restructuring of the circulatory system occurred. The heart of amphibians is divided into the venous sinus, which flows into the right atrium, left atrium, common ventricle, and arterial cone. 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 arterial cone. The aortic arches form the dorsal aorta. In the venous system, the posterior cardinal veins are reduced, functionally replaced by the unpaired posterior vena cava. The anterior cardinal veins are called the superior (internal) jugular, and the Cuvier ducts are called the anterior vena cava. In amphibians, an important additional respiratory organ is the skin, arterial blood from which flows 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 ventilation mechanism of the lungs, the need for skin respiration disappeared. In most of them, the venous sinus and the arterial cone were reduced; the heart consists of two atria and a ventricle, in which there is an internal, usually incomplete (with the exception of crocodiles) septum, which makes it possible to partially separate the flows of arterial and venous blood coming from the left and right atria, and redistribute them in accordance with physiological needs. Reptiles retain 2 aortic arches, from which the right one receives arterial blood, and the left one - mixed; venous blood enters the pulmonary artery.

In birds and mammals, complete separation 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 portal system of the kidneys, which was present in most primitive vertebrates (except for cyclostomes), is reduced. All these changes in the circulatory system contributed to a significant increase in the general 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, vol. 39, no. 8; Beklemishev V.N. Fundamentals of comparative anatomy of invertebrates. 3rd ed. M., 1964. T. 2; Romer A., \u200b\u200bParsons T. Anatomy of vertebrates. M., 1992.Vol. 2.

It is from the course of biology that we remember about a closed and unclosed circulatory system. But it is to her that living beings owe the coordinated movement of blood through the body, which thereby ensures full-fledged vital activity. 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.

An open circulatory system

This type of circulation is characteristic of the simplest invertebrates, echinoderms, arthropods and brachiopods, as well as hemichordates.

They deliver oxygen and vital elements using diffuse currents. Some living beings have paths for the passage of blood. This is how vessels of a rather primitive appearance appear, interrupted by slit-like spaces, which are called sines or lacunae.

A distinctive feature of an open circulatory system is too low speed of movement in relation to a large volume of blood. It slowly, under low pressure moves between the tissues, and then through the open endings 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, an open circulatory system is intended for the transport of nutrients to the organs, as well as for the removal of waste products. The movement of blood is provided by contractions of the heart, which is located in the posterior section of the aorta (dorsal vessel). It, in turn, branches into arteries, the blood from which is poured out onto the washed internal organs and open cavities. This blood flow system is believed to be imperfect, unlike that found in 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 contained in them does not come into contact with body tissues. This type is typical for humans, other vertebrates, some other groups of animals and annelids. In the former, blood flow occurs due to a well-developed muscular heart. Its contractions are carried out automatically, but regulation by the central nervous system is also possible.

Benefits of a closed blood system

This type is characterized by a rather high pressure. In contrast to an open circulatory system, the speed of blood flow through the vessels is much faster here. At the same time, the time of one turnover is different for all organisms - for some it is twenty minutes, and for some, the blood makes a turnover 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 performed during breathing, and skeletal muscle contractions.

Pulse

It is one of the main characteristics of the heart. With this phenomenon, the periodic expansion of the arteries coincides with the contraction of the heart muscle. The heart rate depends on a large number of reasons: emotional and physical stress, body temperature, overweight. According to generally accepted standards, the pulse rate of an adult should not exceed eighty beats per minute.

In the event that any deviations were revealed during the measurement, this is a reason to think about the presence of heart disease and pay a visit to a specialist. In this case, the opinion of incompetent relatives and neighbors should be ignored.

These are aquatic or terrestrial animals, the body of which consists mainly of soft tissues and is covered with a shell. The body cavity in adults is largely reduced, and the spaces between the organs are filled with connective tissue. The circulatory system includes the heart and blood vessels, the heart is divided into 1 ventricle and several atria. There can be 2 or 4 atria, or there can be only one.

From the vessels, blood is poured into the gaps between the internal organs, where it gives off oxygen, after which it is collected back into the vessels and sent to the respiratory organs. Respiratory organs - lung or gills, covered with a dense network of capillaries. Here the blood is again saturated with oxygen. The blood of molluscs is mostly colorless; it contains a special substance that can bind to oxygen.

The exception is cephalopods, which have an almost closed circulatory system. They have two hearts, both hearts are located in the gills. Blood moves through the capillaries of the gills, then from the main heart it flows to the organs. Thus, the blood flows out into the body cavity partially.

Arthropod circulatory system

An open circulatory system also occurs in the Arthropod type, whose representatives inhabit all possible habitats. A characteristic feature of arthropods is the presence of articulated limbs, which allow them to perform various movements. This type includes classes: Crustaceans, Arachnids, Insects.

There is a heart located above the intestines. It can be in the form of a tube or a bag. From the arteries, blood enters the body cavity, where it gives off oxygen. Gas exchange becomes possible due to the presence of respiratory pigment in the blood. After that, the blood is collected in the veins and enters the gill capillaries, where it is saturated with oxygen.

In crustaceans, the structure of the circulatory system is directly related to the structure of the respiratory system. Their heart is located near the respiratory system. In primitive crustaceans, the heart looks like a tube with holes in each segment of the body; in more developed crustaceans, it looks like a sac. There are primitive crustaceans in which gas exchange occurs through the body wall. In these, the circulatory system may be completely absent. The heart of arachnids is basically a tube with several pairs of holes. In the smallest, it looks like a bag.

The fluid moving through the circulatory system of insects, hemolymph. It is partially located in a special organ - the dorsal vessel, which looks like a tube. The rest washes the internal organs. The dorsal vessel consists of the heart and the aorta. The heart is divided into chambers, their number corresponds to the number of body segments.