The circulatory system of fish. Phylogeny of the main organ systems of vertebrates Phylogeny of the circulatory system Evolution of the arterial system in vertebrates

Fishes

In the heart of fish there are 4 cavities connected in series: sinus venosus, atrium, ventricle and arterial cone/bulb.

• The venous sinus (sinus venosus) is a simple extension of the vein into which blood is collected.
• In sharks, ganoids, and lungfish, the arterial cone contains muscle tissue, several valves, and is able to contract.
• In bony fish, the arterial cone is reduced (it does not have muscle tissue and valves), therefore it is called the "arterial bulb".

The blood in the fish heart is venous, from the bulb/cone it flows to the gills, there it becomes arterial, flows to the organs of the body, becomes venous, returns to the venous sinus.

Lungfish

In lungfish, a "pulmonary circulation" appears: from the last (fourth) gill artery, blood goes through the pulmonary artery (LA) to the respiratory sac, where it is additionally enriched with oxygen and returns through the pulmonary vein (PV) to the heart, to left part of the atrium. Venous blood from the body flows, as it should, into the venous sinus. To limit the mixing of arterial blood from the "pulmonary circle" with venous blood from the body, there is an incomplete septum in the atrium and partly in the ventricle.

Thus, arterial blood in the ventricle is front venous, therefore it enters the anterior branchial arteries, from which a direct road leads to the head. Smart fish brain receives blood that has passed through the gas exchange organs three times in a row! Bathed in oxygen, rogue.

Amphibians

The circulatory system of tadpoles is similar to that of bony fish.

In an adult amphibian, the atrium is divided by a septum into the left and right, in total 5 chambers are obtained:

• venous sinus (sinus venosus), in which, like in lungfish, blood flows from the body
• left atrium (left atrium), into which, as in lungfish, blood flows from the lung
• right atrium (right atrium)
• ventricle
• arterial cone (conus arteriosus).

1) Arterial blood from the lungs enters the left atrium of amphibians, and venous blood from organs and arterial blood from the skin enters the right atrium, thus, mixed blood is obtained in the right atrium of frogs.

2) As you can see in the figure, the mouth of the arterial cone is displaced towards the right atrium, so the blood from the right atrium enters there first, and from the left - to the last.

3) Inside the arterial cone there is a spiral valve (spiral valve), which distributes three portions of blood:

• the first portion of blood (from the right atrium, the most venous of all) goes to the pulmocutaneous artery, to be oxygenated
• the second portion of blood (a mixture of mixed blood from the right atrium and arterial blood from the left atrium) goes to the organs of the body through the systemic artery
• the third portion of blood (from the left atrium, the most arterial of all) goes to the carotid artery (carotid artery) to the brain.

4) In lower amphibians (tailed and legless) amphibians

• the septum between the atria is incomplete, so the mixing of arterial and mixed blood is stronger;
• the skin is supplied with blood not from the skin-pulmonary arteries (where the most venous blood is possible), but from the dorsal aorta (where the blood is medium) - this is not very beneficial.

5) When a frog sits underwater, venous blood flows from the lungs into the left atrium, which, in theory, should go to the head. There is an optimistic version that the heart at the same time starts to work in a different mode (the ratio of the phases of the pulsation of the ventricle and the arterial cone changes), complete mixing of the blood occurs, due to which not completely venous blood from the lungs enters the head, but mixed blood, consisting of venous blood of the left atrium and mixed right. There is another (pessimistic) version, according to which the brain of the underwater frog receives the most venous blood and becomes dull.

reptiles

In reptiles, the pulmonary artery (“to the lung”) and two aortic arches emerge from the ventricle, which is partially divided by a septum. The division of blood between these three vessels occurs in the same way as in lungfish and frogs:

• the most arterial blood (from the lungs) enters the right aortic arch. To make it easier for children to learn right arc the aorta starts from the leftmost part of the ventricle, and it is called the “right arch” because, having rounded the heart on right, it is included in the composition of the spinal artery (how it looks - you can see in the next and following figure). Depart from the right arc carotid arteries- the most arterial blood enters the head;
• mixed blood enters the left aortic arch, which goes around the heart on the left and connects to the right aortic arch - the spinal artery is obtained, which carries blood to the organs;
• the most venous blood (from the organs of the body) enters the pulmonary arteries.

crocodiles

Crocodiles have a four-chambered heart, but they still mix blood through a special foramen of Panizza between the left and right aortic arches.

True, it is believed that mixing does not occur normally: due to the fact that in the left ventricle there is more high pressure, blood from there flows not only into the right aortic arch (Right aorta), but also - through the panician opening - into the left aortic arch (Left aorta), thus, the organs of the crocodile receive almost completely arterial blood.

When a crocodile dives, the blood flow through its lungs decreases, the pressure in the right ventricle increases, and the flow of blood through the foramen panicia stops: blood from the right ventricle flows along the left aortic arch of an underwater crocodile. I don’t know what the point is: all the blood in the circulatory system at this moment is venous, why redistribute where? In any case, blood from the right aortic arch enters the head of the underwater crocodile - when the lungs are not working, it is completely venous. (Something tells me that the pessimistic version is also true for underwater frogs.)

Birds and mammals

The circulatory systems of animals and birds in school textbooks are set out very close to the truth (all other vertebrates, as we have seen, are not so lucky with this). The only trifle that is not supposed to be said at school is that in mammals (C) only the left aortic arch has been preserved, and in birds (B) only the right one (under the letter A is the circulatory system of reptiles in which both arches are developed) - there is nothing else interesting in the circulatory system of either chickens or humans. Is that the fruit ...

Fruit

Arterial blood, received by the fetus from the mother, comes from the placenta through the umbilical vein (umbilical vein). Part of this blood enters the portal system of the liver, part bypasses the liver, both of these portions eventually flow into the inferior vena cava (interior vena cava), where they mix with the venous blood flowing from the organs of the fetus. Once in the right atrium (RA), this blood is once again diluted with venous blood from the superior vena cava (superior vena cava), thus, in the right atrium, the blood is completely mixed. At the same time, a little venous blood from non-working lungs enters the left atrium of the fetus - just like a crocodile sitting under water. What are we going to do, colleagues?

The good old incomplete septum comes to the rescue, over which the authors of school textbooks on zoology laugh so loudly - the human fetus has an oval hole (Foramen ovale) right in the septum between the left and right atrium, through which mixed blood from the right atrium enters the left atrium. In addition, there is a ductus arteriosus (Dictus arteriosus), through which mixed blood from the right ventricle enters the aortic arch. Thus, mixed blood flows through the fetal aorta to all its organs. And to the brain too! And we molested frogs and crocodiles !! But themselves.

testiki

1. Cartilaginous fish lack:
a) swim bladder
b) spiral valve;
c) arterial cone;
d) chord.

2. Composed circulatory system mammals have:
a) two aortic arches, which then merge into the dorsal aorta;
b) only the right aortic arch
c) only the left aortic arch
d) only the abdominal aorta, and the aortic arches are absent.

3. As part of the circulatory system in birds there is:
A) two aortic arches, which then merge into the dorsal aorta;
B) only the right aortic arch;
C) only the left aortic arch;
D) only the abdominal aorta, and the aortic arches are absent.

4. The arterial cone is present in
A) cyclostomes;
B) cartilaginous fish;
B) cartilaginous fish;
D) bony ganoid fish;
D) bony fish.

5. Classes of vertebrates in which blood moves directly from the respiratory organs to the tissues of the body, without first passing through the heart (select all the correct options):
A) bone fish;
B) adult amphibians;
B) reptiles
D) Birds;
D) mammals.

6. The heart of a turtle in its structure:
A) three-chamber with an incomplete septum in the ventricle;
B) three-chamber;
B) four-chamber;
D) four-chamber with a hole in the septum between the ventricles.

7. The number of circles of blood circulation in frogs:
A) one in tadpoles, two in adult frogs;
B) one in adult frogs, tadpoles do not have blood circulation;
C) two in tadpoles, three in adult frogs;
D) two in tadpoles and in adult frogs.

8. In order for the carbon dioxide molecule, which passed into the blood from the tissues of your left foot, to be released into the environment through the nose, it must pass through all of the listed structures of your body with the exception of:
A) right atrium
B) pulmonary vein;
B) alveoli of the lungs;
D) pulmonary artery.

9. Two circles of blood circulation have (select all correct options):
A) cartilaginous fish;
B) ray-finned fish;
B) lungfish
D) amphibians;
D) reptiles.

10. A four-chambered heart has:
A) lizards
B) turtles;
B) crocodiles
D) birds;
D) mammals.

11. Before you is a schematic drawing of the heart of mammals. Oxygenated blood enters the heart through the vessels:

A) 1;
B) 2;
IN 3;
D) 10.

12. The figure shows arterial arches:
A) lungfish
B) tailless amphibian;
B) tailed amphibian;
D) reptile.

Characteristic signs of chordates:

• three-layer structure;
• secondary body cavity;
• the appearance of a chord;
• the conquest of all habitats (water, land-air).

In the course of evolution, organs were improved:

• movement;
• breeding;
• breathing;
• blood circulation;
• digestion;
• feelings;
• nervous (regulating and controlling the work of all organs);
• body covering changed.

The biological meaning of all living things:

general characteristics

inhabit- freshwater reservoirs; in sea water.

Lifespan- from several months to 100 years.

Dimensions- from 10 mm to 9 meters. (Pisces grow all their lives!).

Weight- from a few grams to 2 tons.

Fish are the most ancient primary aquatic vertebrates. They can only live in water, most species are good swimmers. The class of fish in the process of evolution was formed in the aquatic environment, the characteristic features of the structure of these animals are associated with it. The main type of translational movement is lateral wave-like movements due to contractions of the musculature of the caudal region or the whole body. The pectoral and ventral paired fins perform the function of stabilizers, serve to raise and lower the body, turn stops, slow smooth movement, and maintain balance. The unpaired dorsal and caudal fins act like a keel, giving the fish's body stability. The mucous layer, on the surface of the skin, reduces friction and promotes rapid movement, and also protects the body from pathogens of bacterial and fungal diseases.

The external structure of the fish

Lateral line

The organs of the lateral line are well developed. The lateral line senses the direction and strength of the water current.

Due to this, even blinded, she does not run into obstacles and is able to catch moving prey.

Internal structure

Skeleton

The skeleton is a support for well-developed striated muscles. Some muscle segments have partially rebuilt, forming groups of muscles in the head, jaws, gill covers, pectoral fins, etc. (eye, supragillary and hypogillary muscles, muscles of paired fins).

swim bladder

Above the intestines is a thin-walled sac - a swim bladder filled with a mixture of oxygen, nitrogen and carbon dioxide. The bubble was formed from an outgrowth of the intestine. The main function of the swim bladder is hydrostatic. By changing the pressure of gases in the swim bladder, the fish can change the depth of immersion.

If the volume of the swim bladder does not change, the fish is at the same depth, as if hanging in the water column. When the volume of the bubble increases, the fish rises up. When lowering, the reverse process occurs. The swim bladder in some fish can participate in gas exchange (as an additional respiratory organ), act as a resonator in the reproduction of various sounds, etc.

body cavity

Organ system

digestive

The digestive system begins at the mouth. In perch and other predatory bony fish on the jaws and many bones oral cavity there are numerous small sharp teeth that help to capture and hold prey. There is no muscular tongue. Through the pharynx into the esophagus, food enters the large stomach, where it begins to be digested under the action of hydrochloric acid and pepsin. Partially digested food enters the small intestine, where the ducts of the pancreas and liver flow. The latter secretes bile, which accumulates in the gallbladder.

At the beginning small intestine blind processes flow into it, due to which the glandular and absorptive surface of the intestine increases. Undigested residues are excreted into the hindgut and through the anus are removed to the outside.

Respiratory

The respiratory organs - gills - are located on four gill arches in the form of a row of bright red gill filaments, covered on the outside with numerous very thin folds that increase the relative surface of the gills.

Water enters the mouth of the fish, is filtered through the gill slits, washes the gills, and is thrown out from under the gill cover. Gas exchange occurs in numerous gill capillaries, in which blood flows towards the water surrounding the gills. Fish are able to assimilate 46-82% of the oxygen dissolved in water.

Opposite each row of gill filaments are whitish gill rakers, which are of great importance for the nutrition of fish: in some they form a filtering apparatus with an appropriate structure, in others they help to keep prey in the oral cavity.

circulatory

The circulatory system consists of a two-chambered heart and blood vessels. The heart has an atrium and a ventricle.

excretory

The excretory system is represented by two dark red ribbon-like kidneys lying below the spinal column almost along the entire body cavity.

The kidneys filter waste products from the blood in the form of urine, which passes through the two ureters to the bladder, opening outward behind the anus. A significant part of the poisonous decay products (ammonia, urea, etc.) are excreted from the body through the gill filaments of fish.

nervous

The nervous system looks like a hollow tube thickened in front. Its anterior end forms the brain, in which there are five sections: anterior, intermediate, midbrain, cerebellum and medulla oblongata.

The centers of different sense organs are located in different parts of the brain. The cavity inside the spinal cord is called the spinal canal.

sense organs

taste buds, or taste buds, are located in the mucous membrane of the oral cavity, on the head, antennae, elongated rays of the fins, scattered over the entire surface of the body. Tactile bodies and thermoreceptors are scattered in the superficial layers of the skin. Predominantly on the head of the fish, receptors for electromagnetic sensation are concentrated.

two big eyes are on the sides of the head. The lens is round, does not change shape and almost touches the flattened cornea (therefore, fish are short-sighted and see no further than 10-15 meters). In most bony fish, the retina contains rods and cones. This allows them to adapt to changing light conditions. Most bony fish have color vision.

hearing organs represented only by the inner ear, or membranous labyrinth, located on the right and left in the bones of the back of the skull. Sound orientation is very important for aquatic animals. The speed of sound propagation in water is almost 4 times greater than in air (and is close to the sound permeability of fish body tissues). Therefore, even a relatively simple hearing organ allows fish to perceive sound waves. The organs of hearing are anatomically related to the organs of balance.

From the head to the caudal fin, a series of holes stretches along the body - lateral line. The holes are connected with a canal immersed in the skin, which strongly branches on the head and forms a complex network. The lateral line is a characteristic sense organ: thanks to it, fish perceive water vibrations, the direction and strength of the current, waves that are reflected from various objects. With the help of this organ, fish navigate in water flows, perceive the direction of movement of prey or a predator, and do not run into solid objects in barely transparent water.

reproduction

Fish breed in water. Most species lay eggs, fertilization is external, sometimes internal, in these cases live birth is observed. The development of fertilized eggs lasts from several hours to several months. The larvae that emerge from the eggs have a leftover yolk sac with a reserve nutrients. At first they are inactive, and feed only on these substances, and then they begin to actively feed on various microscopic aquatic organisms. After a few weeks, the larva develops into a scaly and adult fish-like fry.

Fish spawning occurs at different times of the year. Most freshwater fish lay their eggs among aquatic plants in shallow water. The fecundity of fish is on average much higher than the fecundity of terrestrial vertebrates, this is due to the large death of eggs and fry.

The superclass Pisces belongs to the phylum Chordates. They live in water. And they have a number of features associated with life in it.

The circulatory system of fish

Like all chordates, fish have a closed circulatory system. In both bony and cartilaginous fish, blood from the heart enters the blood vessels, and from them returns to the heart. In the heart of these animals, two chambers - the atrium and the ventricle. Vessels are of three types:

• arteries;
• veins;
• capillaries.

Arteries carry blood away from the heart and the walls of these vessels are thicker to withstand the pressure generated by the heart. Through the veins, blood returns to the heart, while the pressure in them drops, so their walls are thinner. And capillaries are the smallest vessels, the walls of which consist of one layer of cells, because their main function is gas exchange.

Fish circulation

Before considering the process of blood circulation itself, it is necessary to recall the varieties of blood. It is arterial, in which there is a lot of oxygen, and venous - saturated with carbon dioxide. Thus, the type of blood has nothing to do with the name of the vessels through which it flows, but only with its composition. As for fish, they have venous blood in both chambers of the heart, and there is only one circle of blood circulation.

Consider sequentially the movement of blood:

1. The ventricle, contracting, pushes venous blood into the branchial arteries.
2. In the gills, arteries branch into capillaries. This is where gas exchange takes place and blood is converted from venous to arterial.
3. From capillaries arterial blood is collected in the abdominal aorta.
4. The aorta branches into the arteries of the organs.
5. In the organs, the arteries again branch into capillaries, where the blood gives off oxygen and takes carbon dioxide, from arterial to venous.
6. Venous blood from the organs is collected in the veins, which carry it to the heart.
7. The circle of blood circulation in the atrium ends.

Thus, although fish cannot be called warm-blooded animals, their organs and tissues receive pure arterial blood. This helps fish live in the cold waters of the Arctic and Antarctic, and also not die in fresh water in winter.

In the circulatory system of fish, in comparison with lancelets, a real heart appears. It consists of two chambers, i.e. double chambered fish heart. The first chamber is the atrium, the second chamber is the ventricle of the heart. Blood first enters the atrium, then is pushed into the ventricle by muscle contraction. Further, as a result of its contraction, it pours into a large blood vessel.

The heart of fish is located in the pericardial sac located behind the last pair of gill arches in the body cavity.

Like all chords, closed circulatory system of fish. This means that nowhere along the path of its passage, the blood does not leave the vessels and does not pour into the body cavity. To ensure the exchange of substances between the blood and the cells of the whole organism, large arteries (vessels that carry blood saturated with oxygen) gradually branch into smaller ones. The smallest vessels are capillaries. Having given up oxygen and taken in carbon dioxide, the capillaries again unite into larger vessels (but already venous).

Fish only one circle of blood circulation. With a two-chambered heart, it cannot be otherwise. In more highly organized vertebrates (starting with amphibians), a second (pulmonary) circle of blood circulation appears. But these animals also have a three-chambered or even four-chambered heart.

Venous blood flows through the heart that gives oxygen to the cells of the body. Further, the heart pushes this blood into the abdominal aorta, which goes to the gills and branches into the afferent branchial arteries (but despite the name "arteries" they contain venous blood). In the gills (specifically, in the gill filaments), carbon dioxide is released from the blood into the water, and oxygen seeps from the water into the blood. This happens as a result of the difference in their concentration (dissolved gases go to where they are less). Enriched with oxygen, the blood becomes arterial. The efferent branchial arteries (already with arterial blood) flow into one large vessel - the dorsal aorta. It runs under the spine along the body of the fish and smaller vessels originate from it. The carotid arteries also depart from the dorsal aorta, going to the head and supplying blood, including the brain.

Before entering the heart, venous blood passes through the liver, where it is cleared of harmful substances.

There are slight differences in the circulatory system of bony and cartilaginous fish. Mostly it's about the heart. In cartilaginous fish (and some bony fish), the dilated portion of the abdominal aorta contracts along with the heart, while in most bony fish it does not.

The blood of fish is red, it contains red blood cells with hemoglobin, which binds oxygen. However, fish erythrocytes are oval in shape, not disc-shaped (as, for example, in humans). The amount of blood flowing through the circulatory system is less in fish than in terrestrial vertebrates.

The heart of fish does not beat often (about 20-30 beats per minute), and the number of contractions depends on the ambient temperature (the warmer, the more often). Therefore, their blood does not flow as fast and therefore their metabolism is relatively slow. This, for example, affects the fact that fish are cold-blooded animals.

In fish, the hematopoietic organs are the spleen and the connective tissue of the kidneys.

Despite the fact that the described circulatory system of fish is characteristic of the vast majority of them, it differs somewhat in lungfish and lobe-finned fish. In lungfish, an incomplete septum appears in the heart and a semblance of a pulmonary (second) circulation appears. But this circle does not pass through the gills, but through the swim bladder, turned into a lung.

Fish are vertebrates. Such organisms have a skull, spine and paired limbs, in this case fins. The superclass Pisces is divided into two classes:

• Bone fish.
• Cartilaginous fish.

The class of bony fish, in turn, is divided into several superorders:

• Cartilaginous ganoids.
• Lungfish.
• Cross-finned fish.
• Bony fish.

The main difference between all fish is the presence of one circle of blood circulation, as well as a two-chambered heart, which is filled with venous blood, with the exception of only lobe-finned and lungfish fish. The structure of the circulatory system of fish (bone and cartilage) is similar, but still has some differences. Both schemes will be discussed below.

The circulatory system of cartilaginous fish

The heart of cartilaginous fish consists of two parts - chambers. These chambers are called the ventricle and the atrium. Near the atrium is a wide thin-walled venous sinus, venous blood flows into it. At the end (when viewed from the side of the blood flow) part of the ventricle is an arterial cone, which is part of the ventricle, but looks like the beginning of the abdominal aorta. In all parts of the heart there are striated muscles.

The abdominal aorta arises from the conus arteriosus. The five pairs of branchial arteries originate at the abdominal aorta and branch off to the gills. The arteries in which blood flows towards the gill filaments are called the afferent branchial arteries, and in which oxidized blood flows from the gill filaments, the efferent branchial arteries.

The efferent arteries flow into the roots of the aorta, and they, in turn, merge and form the dorsal aorta - the main arterial trunk. It is located under the spine and supplies blood to all internal organs fishes. The carotid arteries run from the roots of the aorta to the head.

From the head, venous blood flows through the paired cardinal veins, also called the jugular veins. Blood from the trunk flows through the paired posterior cardinal veins. They merge with the jugular veins near the heart and form the Cuvier ducts of the corresponding side, then flow into the venous sinus.

In the kidneys, the cardinal veins form the so-called portal circulatory system. In the axillary vein, blood enters from the intestines. The portal circulatory system is formed in the liver: the intestinal vein brings blood, and the hepatic vein carries it into the venous sinus.

The circulatory system of bony fish

In almost all species of bony fish, the abdominal aorta has a swelling, which is called the arterial bulb. It consists of smooth muscle, but outwardly similar to the arterial cone of the circulatory system of cartilaginous fish. It is worth noting that the arterial bulb cannot pulsate on its own.

There are only four pairs of arterial arches (afferent and efferent arteries). In most species of bony fish, the venous system is arranged so that the right cardinal vein is continuous, and the left forms the portal circulatory system in the left kidney.

The circulatory system of fish is simpler than that of amphibians and reptiles, but it has some rudiments of vessels, like that of frogs and snakes.

Superorder lungfish

Considering how the circulatory system of fish is arranged, it is worth paying special attention to lungfish, because they have some features.

The most important feature of this superorder is the presence, in addition to gill respiration, of pulmonary respiration. One or two bubbles act as organs for pulmonary respiration, which open near the esophagus on the ventral side. But these formations are not similar in structure to the swim bladder of bony fish.

Blood flows to the lungs through vessels that branch off from the fourth pair of branchial arteries. They are similar in structure to the pulmonary arteries. Vessels come from the so-called lungs. They carry blood to the heart. These special vessels are homologous in structure to the pulmonary veins of terrestrial animals.

The atrium is partially divided by a small septum into right and left parts. From the pulmonary veins, blood enters the left half of the atrium, and all the blood from the posterior vena cava and the Cuvier ducts enters the right half. The vena cava is absent in fish; it is characteristic only of terrestrial animal species.

The circulatory system of fish of the superorder Lungfish is evolved and is a harbinger of the development of this system of terrestrial vertebrates.

Composition of the blood

• Colorless liquid - plasma.
• Erythrocytes are red blood cells. They contain hemoglobin, which turns blood red. These same elements carry oxygen through the blood.
• Leukocytes are white blood cells. They take part in the destruction of foreign microorganisms that have entered the body of the animal.
• Platelets affect blood clotting.
• Other elements of the blood.

The relative mass of blood to body weight in fish is approximately 2-7%. This is the smallest percentage among all vertebrates.

The value of the circulatory system is multifunctional. Thanks to it, tissues, organs and cells of a living organism receive oxygen, minerals, liquid. The blood carries out some metabolic products: carbon dioxide, slags, etc.

It is worth noting that the lymphatic system acts as an intermediary between blood and tissues. lymphatic system is a vascular system that contains a colorless liquid called lymph.

General conclusions

Blood refers to connective tissue. It penetrates into the bloodstream from the intercellular space. The circulatory system of fish is not much different from other vertebrates.