Circulatory systems in animals. Which circulatory system is usually called closed? 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. Delivery of heat and nutrients to all organs human body, without which existence is impossible, is also the 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 it again gathers to the heart. Slow circulation of hemolymph leads to passive breathing and poor oxygen supply to the body.

In arthropods it is not closed circulatory system intended for transport to organs nutrients, as well as removal of waste products. The movement of blood 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 internal organs and open cavities being washed. 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 contained 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 reductions are carried out automatically, but it is also possible to regulate the central nervous system.

Advantages of a closed blood system

This type is characterized by quite high 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. Heart rate depends on large quantity reasons: emotional and physical exercise, 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.

CIRCULATORY SYSTEM CIRCULATORY SYSTEM

(systema vasorum), a system of vessels and cavities through which blood or hemolymph circulates. There are 2 types of K. with: open, or lacunar (echinoderms, arthropods, brachiopods, mollusks, hemichordates, tunicates, etc.), and closed (nemerteans, annelids and all vertebrates). In animals with unclosed K. s. the vessels are interrupted by slit-like spaces (lacunae, sinuses) that do not have their own. walls Blood (called hemolymph in this case) enters directly. contact with all tissues of the body. In arthropods, brachiopods and mollusks, a heart appears (a pulsating section of a vessel or a muscular organ not divided into chambers), located on the dorsal side of the body. In some arthropods K. s. simplified, because it means that part of the breath. functions transferred from K. s. to the tracheas, delivering O2 directly to the tissues. In mollusks, all transitions from open-loop c. are observed. to almost closed (cephalopods). K. s. in all vertebrates mainly is constructed in the same way: they all have a heart and an aorta, arteries, arterioles, capillaries, venules and veins, organized according to a single principle. IN closed K. s. the arteries are divided into vessels of ever smaller diameter and, finally, pass into arterioles, from which blood enters the capillaries. The latter form a complex network, from which blood flows first into small vessels - venules, and then into increasingly larger ones - veins. Cyclostomes and fish (except lungfishes) have one circulation. Lungfishes and terrestrial vertebrates have 2 circulations. In a small circle, venous blood from the heart is directed through the pulmonary arteries to the lungs and returns to the heart through the pulmonary veins. By big circle arterial blood is sent to the head, to all organs and tissues of the body, and returns through the cardinal or vena cava. All vertebrates have portal systems. With the formation of the pulmonary circulation during the evolution of vertebrates, progressive differentiation of the parts of the heart occurs. In birds and mammals, this led to the emergence of a four-chambered heart and to the complete separation of arterial and venous blood flows in it. (see CIRCULATION, HEART), (see 53_TABLE_53).

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected - M.: Sov. Encyclopedia, 1986.)

(the cardiovascular system), designed to transport blood (in arthropods - hemolymph). Carries out the transport of oxygen and carbon dioxide, nutrients and metabolic products excreted through the kidneys, skin, lungs and other organs, as well as thermoregulation in warm-blooded animals. The central link of the circulatory system is usually heart- a pulsating organ or section of the abdominal aorta with thickening of the muscular walls that provide blood flow in the system. The blood vessels through which blood flows from the heart form the arterial system, and the vessels that collect blood and carry it to the heart form the venous system. The exchange of substances between the blood and body tissues is carried out using the smallest vessels - capillaries, penetrating organs and most tissues.
The circulatory system in which blood circulates through arteries, capillaries and veins is called closed. It is characteristic of annelids and most chordates. In an open circulatory system, the vessels are interrupted by slit-like spaces that do not have their own walls. Entering them from the arterial system, hemolymph washes all internal organs and collects in the heart (a pulsating vessel) through paired openings - ostia, which have valves. An open circulatory system is characteristic of arthropods, mollusks, and echinoderms. In insects it is poorly developed, and the hemolymph does not carry oxygen, since these animals have a well-branched system trachea.
In vertebrates, the pulsating organ - the heart - is located on the ventral side of the body under the notochord and the digestive tract. Aquatic vertebrates (cyclostomes, fish and amphibian larvae) have one circulation and a two-chambered heart with venous blood. Terrestrial vertebrates have two circles of blood circulation and a three-chambered heart with mixed blood or a four-chambered heart with separate blood - arterial and venous.
The arterial system of aquatic vertebrates consists of the abdominal aorta, which branches into paired gill afferent arteries, then into capillaries in which gas exchange occurs. The efferent branchial arteries flow into the dorsal aorta, which carries blood to the body, tail and internal organs, and in front along the carotid arteries - to the head. In amphibians, one of the pairs of gill arteries forms the pulmonary circle, but there is also a large cutaneous artery. Reptiles have two aortic arches (right and left), carrying mixed blood and merging into the dorsal aorta, and a pulmonary artery with a predominance of venous blood. In birds, the right aortic arch, and in mammals, the left one carries arterial blood, and the pulmonary artery carries venous blood.
The venous system of aquatic vertebrates consists of paired anterior and posterior cardinal veins, which drain into the venous sinus of the tail vein, two renal portal veins, the hepatic portal vein, and the hepatic vein, which drains into the sinus venosus. In terrestrial vertebrates, the veins of the head and forelimbs form the anterior vena cava system, and the veins of the organs of the trunk and hind limbs form the posterior vena cava.
Humans have a closed circulatory system. Blood circulating through the blood vessels ensures the exchange of substances between the body and the external environment (it delivers oxygen and nutrients to the tissues and removes metabolic products and carbon dioxide). 2 circles extend from the heart blood circulation- big and small.
The small (pulmonary) circle starts from the right ventricle of the heart with its trunk pulmonary artery, through which venous blood flows, delivered to the pulmonary capillaries, where it gives off carbon dioxide, is saturated with oxygen, turning into arterial blood. From the lungs, arterial blood enters the four pulmonary veins left atrium and as a result of contraction through the atrioventricular orifice into the left ventricle. Thus, venous blood flows in the arteries of the pulmonary circle, and arterial blood flows in the veins. The systemic circulation begins from the left ventricle with the largest vessel - aorta. It branches into numerous arteries of different sizes. The right and left coronary (coronary) arteries, which supply blood to the heart, depart directly from the aorta. Small arteries branch into thousands of arterioles, which form a network of capillaries that supply blood to the entire body. From the capillaries, the blood, after releasing oxygen and nutrients and being saturated with carbon dioxide and other dissimilation products, collects into venules, then into veins. The veins of the great circle collect blood from all parts of the body, gradually merging into large venous trunks, which flow into the superior and inferior vena cava, and they, in turn, into the right atrium. The superior vena cava receives blood from the venous system of the head, neck, upper limbs And chest cavity; inferior vena cava - from lower limbs, abdominal cavity and pelvis. Special meaning in the circulatory system has the so-called. portal (portal) system of the liver (gate, or port). The portal vein collects blood from the stomach, pancreas, spleen, and intestines and drains it to the liver. It branches into hepatic capillaries passing between the liver cells, where the blood is released from toxins (antitoxic, or barrier, function) and the deposition of nutrients (depot function). Connecting, the capillaries form the hepatic vein, which drains blood into the inferior vena cava. Presence in the walls blood vessels sensitive and vasomotor receptors ensure the response of the circulatory system to internal and external stimuli by changing vascular tone, redistributing blood supply, etc.

.(Source: “Biology. Modern illustrated encyclopedia.” Chief editor A. P. Gorkin; M.: Rosman, 2006.)

See what "CIRCULATORY SYSTEM" is in other dictionaries:

Big encyclopedic Dictionary

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Modern encyclopedia

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Any circulatory system must include circulating fluid ( blood , lymph, hemolymph), vessels through which fluid is transported (or parts of the body cavity) and a pulsating organ that ensures the movement of fluid throughout the body (this organ is usually the heart). Blood vessels are divided into arteries, through which blood flows from the heart, and veins, through which blood returns to the heart. The walls of blood vessels in mammals consist of three layers of tissue: squamous endothelium, smooth muscle and outer collagen fibers. Arteries and veins in organs branch into smaller vessels - arterioles and venules, and these, in turn, branch into microscopic capillaries passing between the cells of almost all tissues. In the described system, the blood is enclosed in vessels along its entire path and does not come into contact with body tissues; metabolism occurs only through the walls of the vessels. Such a system is called closed; it exists in annelids , vertebrates and some other groups of animals.

In an open circulatory system, arteries open into a system of cavities that form the hemocoel. Blood moves slowly between tissues under low pressure and is collected again towards the heart through the open ends of the venous vessels. Unlike a closed system, here the distribution of blood between tissues is practically not regulated. An open system exists, for example, in arthropods.

Annelids have a well-developed closed circulatory system. Periodic contractions of the dorsal vessel drive blood to the anterior end of the animal; a series of valves prevent blood from flowing in the opposite direction. Five pairs of pulsating “false” hearts connect the dorsal vessel with the abdominal one; Heart valves allow blood to pass only towards the abdominal vessel. After passing through the abdominal vessel, the blood enters the organs of the body; it eventually reassembles in the dorsal vessel. The blood of annelids carries oxygen and nutrients throughout the body, and takes away carbon dioxide and metabolic waste.

The circulatory system of arthropods is not closed. It is designed to transport nutrients to the organs and remove waste products (remember that gas exchange in this type of animal is carried out through trachea). Blood flows through the spinal vessel - the aorta; movement is ensured by contractions of the heart located in the posterior portion of the spinal vessel. The aorta branches into arteries, from which blood flows into open cavities and washes the internal organs.

In vertebrates, blood flow is ensured by contractions of a well-developed muscular heart. The backflow of blood is prevented by the heart valve system. Heart contractions occur automatically, but can be regulated by the central nervous system.

U fish blood, making a full circle in the body, passes through the heart only once; they say that they have one circle of blood circulation. When the heart contracts, blood is pushed into abdominal aorta. The gill arteries bring oxygen-poor blood to the gills, where it is saturated with oxygen in the thinnest capillaries. From the efferent branchial arteries, blood enters the epibranchial arteries, and from there passes into the dorsal aorta. Extending forward from the dorsal aorta carotid arteries carry blood to the head; Numerous arteries branching from the dorsal aorta at the back of the body supply blood to the internal organs.

Even from a school biology course, many people 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 throughout the body is carried out, which naturally indicates the provision of full vital functions. Without normal blood circulation, thanks to which all useful substances and heat are delivered to all organs of our body, a person would not be able to live even a day. In addition, without blood circulation there would be no metabolic processes that have an impact on metabolic rate.

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

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

Not everyone knows that evolutionary processes took place in the circulatory system, which, one way or another, influenced its development. The first time you heard this was back in school, from someone who taught you biology. The circulatory system first 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.

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

Key Features

It is believed that an 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 circulatory circles, which are divided into small and large. Under normal conditions, 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 fairly high pressure.
• The speed of blood circulation through the vessels. An interesting fact is that the time it takes for one blood circulation is different for everyone, for example, for small bugs it takes at least twenty minutes to complete one circle, and for a dog it takes sixteen seconds.

In the human body, blood circulates through the veins, vessels and arteries due to the contraction of the heart muscles, 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 throughout the body, which a person may not know about, or hear about them for the first time in his life.

These factors are generally considered to include:

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

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

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