Circulatory systems of vertebrates (complex). The special structure of the crocodile's heart can help it with digestion The latest data from scientists

I'll tell you a story that happened a few years ago. Now I am writing a school textbook on zoology according to a program in which I myself participated. When this version of the program was first conceived, I convinced the ministerial official that before systematic study separate groups you need to consider a fairly large topic that will talk about animals in general.

“Okay, where should I start?” - the official asked me. I said that the way animals live is determined primarily by what they eat and how they move. This means we need to start with a variety of ways of eating. “What are you talking about!” my interlocutor exclaimed. “How can I take such a program to the minister? He will immediately ask why we instill in children that the most important thing is food!”

I tried to argue. In general, the division of living organisms into kingdoms (animals, plants, fungi and others) is associated primarily with the method of nutrition, which, in turn, determines the features of their structure. The characteristics of multicellular animals are a consequence of the fact that they need external sources organic matter and at the same time they do not absorb them through the surface of the body, but eat them in pieces. Animals are creatures that eat other organisms or their parts! Alas, my interlocutor was adamant. The minister will be primarily interested in the educational aspect of the program.

Thinking about how to organize the introductory part differently, I then made an unforgivable mistake. My next idea was the proposal to start studying the zoology course with diversity life cycles. When my interlocutor realized that I was going to consider reproduction, not food, as the “main thing in life”, he seemed to think that I was making fun of him... In the end I wrote something that, as I hoped, no one won't be shocking. Then methodologists worked their magic on this program, corrected everything in it that they did not understand, and replaced the formulations with those that were in use in historical eras, when these same methodologists studied at pedagogical institutes. Then the ill-fated program was corrected by officials, then it was rethought in the spirit of new guidelines, then... - in general, I’m writing a textbook on my “own” program and I don’t get tired of swearing.

And I remembered this sad story because I was once again convinced: the most important thing for animals is the notorious “food”. When we compare different groups of our relatives with each other, we often do not realize what characteristics led them to success or failure. Do you know, for example, what has become one of the main trump cards of mammals? A successful schoolchild will name feeding offspring with milk, warm-bloodedness, high development nervous system or some other property that is made possible by sufficient energy obtained from food. And one of the main trump cards of mammals is the structure of the jaws and teeth!

Try moving your lower jaw: up and down, left and right, back and forth. Its “suspension” allows movement in all three planes! In addition, on the jaws of mammals there are teeth, the structure of which is determined by the task assigned to them - to pierce, crush, grind, cut, crush, bite, tear, hold, gnaw, crush, pry, grind, scrape, etc. Our jaws are an evolutionary biomechanical masterpiece. Apart from mammals, almost no land vertebrates are capable of biting off pieces of food! A few exceptions include the archaic hatteria, which can saw off the head of a petrel chick with its jaws, and turtles, which abandoned teeth in favor of a horny scissor-shaped beak. AND birds of prey, and crocodiles do not bite off pieces of food, but simply tear them off - resting with their claws (the first) or spinning with their whole body (the second).

By the way, about crocodiles - this column is dedicated primarily to them. Thanks to sophisticated experiments, biologists from the University of Utah were able to learn something new about the functioning of the heart of these reptiles. But first, a few more words about school biology.

Some feeding features biological material have been preserved from those times when the school was supposed to form a materialistic worldview, promoting evolution. Generally speaking, the fact of evolution has no special treatment to the “materialism-idealism” dilemma (while verbally rejecting mossy diamat, for some reason we still attach excessive importance to this dubious dichotomy). Alas, when instead of modern ideas about evolution some stale dogmas are taught, this only causes damage to the natural scientific worldview. Such dogmas include the linear view of evolution. Think about it, the history of vertebrates is a “bush” of many branches, each of which followed its own path, adapted to its own way of life. A school teacher, jumping from branch to branch of this bush, builds a progressive sequence of " typical representatives": lancelet-perch-frog-lizard-dove-dog. But the frog never tried to become a lizard, it lives its own life, and without taking into account this life (and the backstory of frogs) it is impossible to understand it!

What will the school teacher tell you about crocodiles? He uses them to illustrate the statement that the most progressive animals are those with a four-chambered heart and “warm-blooded” (homeothermic). And - look, children! - a crocodile has a four-chambered heart, almost like those of mammals and birds, but there is only one extra hole left. We see with our own eyes how the crocodile wanted to become a man, but did not get there, stopping halfway.

So, the crocodile has a four-chambered heart. From its right half, blood goes to the lungs, from the left - to the systemic circulation (to the organs that consume the oxygen received in the lungs). But between the bases of the vessels extending from the heart there is a gap - the foramen of Panizzia. During the normal operation of the heart, part of the arterial blood passes through this hole from the left half of the heart to the right half and enters the left aortic arch (look at the picture so as not to get confused in the right-left relationship!). Vessels leading to the stomach depart from the left aortic arch. The right aortic arch departs from the left ventricle, supplying the head and forelimbs. And then the aortic arches merge into the dorsal aorta, which provides blood supply to the rest of the body. Why is it so difficult?

First, let’s figure out why we need two circles of blood circulation at all. Fish make do with one thing: heart - gills - consumer organs - heart. Here the answer is clear. The lungs will not be able to withstand the pressure required to pump blood through the entire body. This is why the right (pulmonary) half of the heart is weaker than the left; That’s why it seems to us that the heart is located in the left side of the chest cavity. But why does part of the blood flowing through the systemic circulation (from the left half of the heart) pass through the right, “pulmonary” part of the heart and the left aortic arch in crocodiles? In humans, incomplete separation of blood flows can be caused by heart disease. Why do crocodiles need such a “vice”? The fact is that the heart of a crocodile is not an unfinished human heart, it is “conceived” more complex and can function in two different modes! When the crocodile is active, both aortic arches carry arterial blood. But if the foramen of Panizzia is closed (and crocodiles “know how” to do this), venous blood will flow into the left aortic arch.

Traditionally, such a device is explained by the fact that it supposedly allows a crocodile hidden at the bottom to turn off the pulmonary circulation. In this case, venous blood is sent not to the lungs (which cannot be ventilated anyway), but immediately to the large circle - along the right aortic arch. Somewhat “better” blood will go to the head and to the front legs than to other organs. But if the lungs are disabled, is there much use in circulating the blood?

American biologists have figured out how to test the long-standing assumption that crocodiles transfer blood from one circulation to another not in order to hide, but for the sake of better digestion of food (carbon dioxide is the substrate for the production of acid by the stomach glands). Researchers have verified that in healthy young alligators, in the process of digesting food, the left aortic arch (the one that supplies blood) digestive system) venous, carbon dioxide-enriched blood flows. Then they began to interfere with the heart function of experimental crocodiles using surgical methods. In some of them, the transfer of venous blood to the left aortic arch was forcibly blocked; others underwent surgery simulating such an intervention. The effect was assessed by measuring the activity of gastric secretions and by X-ray observation of the digestion of bovine vertebrae swallowed by crocodiles. In addition, semiconductor sensors were placed in the unfortunate alligators, allowing them to measure their body temperature. As a result of these manipulations, it was possible to convincingly confirm the hypothesis put forward - the transfer of venous blood into the systemic circulation increases the production of acid in the stomach and accelerates the digestion of food.

Crocodiles are capable of feeding on fairly large prey, swallowing the prey whole or in large pieces (remember what we said about the structure of the jaws?). The body temperature of these predators is unstable, and if they do not have time to digest their prey quickly enough, they will simply be poisoned by it. Complicated structure circulatory system and its ability to work in two different modes is a way to activate digestion. And the digestive system of crocodiles justifies its purpose: a series of X-ray photographs show how solid bovine vertebrae “melt” in acid in the stomachs of predators!

So, now we know what is important in the life of crocodiles. What integral beings they are!

D. Shabanov. Heart of a crocodile // Computerra, M., 2008. – No. 10 (726). - pp. 36–37

A log floats down the river -
Oh, how furious it is!
To those who fell into the river,
The nose will be bitten off...

(Crocodile.)

Crocodiles

In terms of their general body structure, crocodiles resemble enlarged lizards.

Types of crocodiles: 1 - gharial; 2 - Nile crocodile; 3 - Chinese alligator

However it is clean external resemblance. Crocodiles differ from lizards not only in size, but also in significant features anatomical structure. They are allocated to a special squad.

The huge mouth of crocodiles is armed sharp teeth, which do not grow to the jaw bones, like all lower vertebrates, but sit in special recesses, cells, and in this respect resemble the teeth of mammals. The brain of crocodiles is well developed and its structure is similar to the more highly organized brain of birds. The lungs of crocodiles have a large volume and complex structure. Thanks to this, animals can stay under water for a long time. The skin of crocodiles, unlike the skin of frogs, is covered with a horny cover that does not allow oxygen to pass through.

The crocodile's heart is not three-chambered, like all other reptiles, but four-chambered. Not only the atrium, but also the ventricle are divided by a longitudinal septum into right and left parts. Pure arterial blood coming from the pulmonary vessels to the left side of the heart does not mix here with venous blood passing through the right atrium and right ventricle. Consequently, in this respect, crocodiles differ from amphibians and other reptiles and are closer to higher vertebrates - birds and mammals, which also have a four-chambered heart.

But still, the circulatory system of crocodiles differs from the circulatory system of higher - warm-blooded - animals: in the latter, only pure arterial blood from the left ventricle of the heart enters the arteries, and in crocodiles venous blood also enters the main arterial trunk, and therefore, the arteries carry mixed blood throughout the body blood. In this respect, crocodiles, despite their four-chambered heart, differ little from other reptiles. And only the head (brain!) receives pure arterial blood from crocodiles through the carotid arteries.

As a result, crocodiles, like all other reptiles, generally remain cold-blooded animals, and their life activity is highly dependent on the surrounding temperature conditions.

So, the higher organization of crocodiles compared to other reptiles is expressed in the structure of the teeth, heart, lungs and brain. These features bring them closer to animals of higher groups - mammals and birds.

Crocodiles are large and strong animals, active predators. The length of some species can reach 6 m. Crocodiles live in countries with warm, tropical climate. Their life is closely connected with bodies of water - on land they usually only bask and lay eggs, and catch prey mainly in the water. Crocodiles are excellent swimmers and divers. Their long, muscular tail is laterally compressed and serves as a good propulsion device, and the toes on the hind legs are partially connected by a swimming membrane. The body of crocodiles is dressed in a shell of horny scutes and scales, which are arranged in longitudinal and transverse rows. On the back, these scutes ossify, making the shell more durable.

Having plunged into the water, the crocodile emerges from it only top part head, where he has slightly raised nostrils and eyes. Let us remember that a frog also raises its flattened head out of the water in the same way; this similarity is explained by the adaptation of both animals to similar living conditions. The main prey of crocodiles are fish and frogs. But they can also attack land animals that come to water and swim across a body of water. Large species of crocodiles are also dangerous to humans.

Crocodile skin has long been used to make suitcases, briefcases and other products. Crocodile meat is also edible.

SCIENCE: The heart of a crocodile

I'll tell you a story that happened a few years ago. Now I am writing a school textbook on zoology according to a program in which I myself participated. When this version of the program was first conceived, I convinced a ministerial official [Not the Russian ministry, don’t worry!] that before systematically studying individual groups, it was necessary to consider a fairly large topic that would talk about animals in general.

I tried to argue. In general, the division of living organisms into kingdoms (animals, plants, fungi and others) is associated primarily with the method of nutrition, which, in turn, determines the features of their structure. The peculiarities of multicellular animals are a consequence of the fact that they need external sources of organic substances and at the same time do not absorb them through the surface of the body, but eat them in pieces. Animals are creatures that eat other organisms or their parts! Alas, my interlocutor was adamant. The minister will be primarily interested in the educational aspect of the program.

Thinking about how to organize the introductory part differently, I then made an unforgivable mistake. My next idea was the proposal to start studying the zoology course with the variety of life cycles. When my interlocutor realized that I was going to consider reproduction, not food, as the “main thing in life”, he seemed to think that I was making fun of him... In the end I wrote something that, as I hoped, no one won't be shocking. Then the methodologists worked their magic on this program, corrected everything in it that they did not understand, and replaced the formulations with those that were in use in historical eras when these same methodologists studied at pedagogical institutes. Then the ill-fated program was corrected by officials, then it was rethought in the spirit of new guidelines, then... - in general, I’m writing a textbook on my “own” program and I don’t get tired of swearing.

And I remembered this sad story because I was once again convinced: the most important thing for animals is the notorious “food”. When we compare different groups of our relatives with each other, we often do not realize what characteristics led them to success or failure. Do you know, for example, what has become one of the main trump cards of mammals? A successful schoolchild will name feeding offspring with milk, warm-bloodedness, high development of the nervous system, or some other property that became possible due to a sufficient amount of energy obtained from food. And one of the main trump cards of mammals is the structure of the jaws and teeth!

Try moving your lower jaw: up and down, left and right, back and forth. Its “suspension” allows movement in all three planes! In addition, on the jaws of mammals there are teeth, the structure of which is determined by the task assigned to them - to pierce, crush, grind, cut, crush, bite, tear, hold, gnaw, crush, pry, grind, scrape, etc. Our jaws are an evolutionary biomechanical masterpiece. Apart from mammals, almost no land vertebrates are capable of biting off pieces of food! A few exceptions include the archaic hatteria, which can saw off the head of a petrel chick with its jaws, and turtles, which abandoned teeth in favor of a horny scissor-shaped beak. Both birds of prey and crocodiles do not bite off pieces of food, but simply tear them off - resting with their claws (the former) or spinning with their whole body (the latter).

By the way, about crocodiles - this column is dedicated primarily to them. Thanks to sophisticated experiments, biologists from the University of Utah have learned something new about the functioning of the hearts of these reptiles. But first, a few more words about school biology.

Some features of the presentation of biological material have been preserved from the times when the school was supposed to form a materialistic worldview, promoting evolution. Generally speaking, the fact of evolution has no special relation to the “materialism-idealism” dilemma (while we verbally reject the mossy dichotomy, for some reason we still attach excessive importance to this dubious dichotomy). Alas, when instead of modern ideas about evolution some stale dogmas are taught, this only causes damage to the natural scientific worldview. Such dogmas include the linear view of evolution. Think about it, the history of vertebrates is a “bush” of many branches, each of which followed its own path, adapted to its own way of life. And the school teacher, jumping from branch to branch of this bush, builds a progressive sequence of “typical representatives”: lancelet-perch-frog-lizard-dove-dog. But the frog never tried to become a lizard, it lives its own life, and without taking into account this life (and the background history of frogs) it is impossible to understand it!

American biologists have figured out how to test the long-standing assumption that crocodiles transfer blood from one circulation to another not in order to hide, but for the sake of better digestion of food (carbon dioxide is the substrate for the production of acid by the stomach glands). Researchers have verified that in healthy young alligators, in the process of digesting food, venous, carbon dioxide-rich blood flows through the left aortic arch (the one that supplies blood to the digestive system). Then they began to interfere with the heart function of experimental crocodiles using surgical methods. In some of them, the transfer of venous blood to the left aortic arch was forcibly blocked; others underwent surgery simulating such an intervention. The effect was assessed by measuring the activity of gastric secretions and by X-ray observation of the digestion of bovine vertebrae swallowed by crocodiles. In addition, semiconductor sensors were placed in the unfortunate alligators, allowing them to measure their body temperature. As a result of these manipulations, it was possible to convincingly confirm the hypothesis put forward - the transfer of venous blood into the systemic circulation increases the production of acid in the stomach and accelerates the digestion of food.

Crocodiles are capable of feeding on fairly large prey, swallowing the prey whole or in large pieces (remember what we said about the structure of the jaws?). The body temperature of these predators is unstable, and if they do not have time to digest their prey quickly enough, they will simply be poisoned by it. The complex structure of the circulatory system and its ability to work in two different modes is a way to activate digestion. And the digestive system of crocodiles justifies its purpose: a series of X-ray photographs show how solid bovine vertebrae “melt” in acid in the stomachs of predators!

So, now we know what is important in the life of crocodiles. What integral beings they are!

From the book Contract Crimes [Murders, thefts, robberies] author Ivanov Alexey Nikolaevich

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From the book Entry & (Not) Exit author Gubin Dmitry

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Crocodiles belong to amphibious creatures, and have always frightened and interested people. The most bloodthirsty reptile in different times deified, but never remained indifferent to her. One of current issues, which worries not only schoolchildren, but also adults, is how many chambers a crocodile’s heart has. An interesting fact is that all amphibious creatures have 3 chambers. But is the crocodile one of them? That's what we'll talk about today. But we will start with a short description of this bloodthirsty predator.

Green predator

Crocodiles belong to the order of aquatic vertebrates. Most often, scientists attribute them to the group of reptiles. Translated from ancient Greek, the word “crocodile” literally means “lizard,” although much larger than other individuals.

Interestingly, of all the animals living on earth, the closest to the crocodile are birds, which are direct descendants of archosaurs.

Currently, crocodiles are semi-aquatic animals, because they began to spend a lot of time on land.

Circulatory system

The heart of the crocodile, which will be discussed in this article, belongs to the circulatory system. What structure does this organ have, how many chambers does it have, and how does the blood supply process generally occur? So. The circulatory system of bloodthirsty reptiles is much more advanced than that of most reptiles, be it lizards, snakes, etc. In most representatives of the species, the heart consists of 3 chambers. But the crocodile has 4 of them! This is an exception to general rules. The heart has 2 atria and 2 ventricles, which are separated by septa. From the right half of the main organ of the circulatory system, blood flows to the lungs, but from the left - to the large circulatory circle. This system is truly unique. In the heart of a crocodile there is a special hole in which venous and arterial blood mixes.

As you can see, the crocodile's heart stopped in its tracks evolutionary development, no longer approaching the human. However, it has two circles of blood circulation, unlike the same fish, which are content with one.

The latest data from scientists

For a long time, famous American biologists could not explain the unique structure of crocodile hearts. They did not understand why the reptile needed not 3, but 4 cameras, but later they came to a phenomenal discovery. And the usual observation of the animal’s lifestyle helped them in this. The thing is that the life of a crocodile is somewhat different from other reptiles. It can lie hidden in the water for several days, waiting for its prey. When the victim is caught, the animal has to eat up to 25 kg at a time raw meat. What kind of digestive system should there be in order to process such an amount of food, assimilate it and continue to live a full life?

The answer lies in the unique structure of the heart, which has 4 chambers. For a long time scientists believed that the glorious organ of the reptile's circulatory system was on an evolutionary path of development, and was approaching the warm-blooded human. Other scientific luminaries, on the contrary, rejected this hypothesis and considered the crocodile to be a real descendant of a warm-blooded creature, which, due to its various reasons it was more profitable to exist as a cold-blooded killer. The heart chambers of a crocodile are not completely closed, for a person this fact threatens a congenital defect, but a reptile feels excellent in this order of things.

American scientists, led by Professor Farmer, experimentally, after a series of tests, proved that the crocodile's heart has such a unique structure only because it has as much blood as possible, rich in carbon dioxide, deliver to the stomach. Which, in turn, began to actively secrete secretions for digesting food. And in the past it was believed that the transfer of blood was necessary for the animal in order to hide in search and wait for the victim on long time.

But it turned out differently. In other words, a predator needs such a complex circulatory system in order to better digest large number raw meat in the shortest possible time.

As you can see, the structure of the circulatory system of a crocodile is unique and ingenious in its own way. This is truly a perfect creation invented by nature. What else is so interesting about this predator?

The animal came into the world about 250 million years ago and first lived on land.
Recognized as a true giant saltwater crocodile, which can be found on the shores of Fiji Island, on the Indian coast. Its length reaches seven meters, and its weight can reach up to a ton. And what’s interesting is that the female’s eggs are no larger than a goose’s.
Just born small crocodile three times longer than the size of its egg.
The reptile swims no worse than a shark: its speed reaches 40-50 km per hour. But on land - about 11 km per hour. Interestingly, despite its enormous size, the animal can jump 2-3 meters out of the water when we're talking about about an attack on the victim.
The jaw of a crocodile can have up to 70 teeth. But the reptile does not chew food with them; they are needed to capture the victim and torment it. Interestingly, teeth can be replaced up to 100 times in a lifetime. And we can talk about the gripping power of a crocodile’s jaw for a very long time.
Predators feed on stones. Yes, you read that right. They help them digest raw food. After all, the crocodile swallows food. Without chewing.
The male has his own harem, which can consist of 10 females. When capturing a large victim, he can invite them to join him for absorption.
Crocodile blood contains a natural antibiotic that kills everything pathogenic bacteria, which come from the outside, and promotes the speedy healing of wounds.

There are many more interesting facts from the life of these wonderful animals that personify cruelty, cunning and bloodthirstiness.

In their opinion, by directing venous blood instead of the lungs to the stomach, the reptile helps itself digest food. And it relieves suffering from muscle aches after a hard hunt.

The life of a crocodile can hardly be called measured. During dry periods these toothy reptiles lie for a long time in the last remaining puddles, slowly using up wisely stored fat reserves. It's a pitiful sight. But when a holiday comes to their street, crocodiles have few equals in their ability to instantly grab, drown or simply break the victim’s neck. Not being able to chew prey with its powerful but rather primitive jaws, the crocodile tears it into pieces in advance and sends it into the stomach in huge pieces.

The total mass of prey can be up to a fifth of the animal’s own weight.
Of course, these reptiles are far from their relatives, pythons, but it’s quite difficult to imagine a person capable of peeling 15–20 kilograms of raw meat, and even with bones, in one sitting.

According to American biologists, the crocodile can thank its unique circulatory system for such amazing digestive abilities. The work of scientists from the University of Utah and the Artificial Heart Institute in Salt Lake City has been accepted for publication in the March issue of the journal Physiological and Biochemical Zoology.

In the body of most vertebrates - including crocodiles - blood moves through the so-called two circles of circulation. In the small, or pulmonary, it, passing through the lungs, is enriched with oxygen and gets rid of carbon dioxide; in the large, or systemic, it supplies oxygen to all organs of the body. Actually, neither one nor the other are full-fledged circles, since they are closed on each other: from the lungs, blood returns to the beginning of the large circle, and from the organs - to the small one.

In the body of mammals and birds, these circles, however, are clearly separated. In a small circle, blood saturated with carbon dioxide, arriving at the right atrium, is driven into the lungs by the right ventricle. The left ventricle sends oxygen-rich blood coming from the left atrium further throughout the body. In fact, a four-chamber heart is two pumps in one, and this division even allows you to maintain significantly lower pressure in the small circle than in the large circle.

Amphibians and reptiles have a three-chambered heart - its atrium is divided in two, but there is only one ventricle, which sends blood further - both to the lungs and to the organs. It is clear that in this case partial mixing of the blood is possible, which makes the system not very effective. However, cold-blooded lizards and amphibians, who for the most part lead a not very active lifestyle, can afford this.

The crocodile heart is a special case.

It has four chambers, but the circles of circulation are not completely separated. In addition, not only the pulmonary artery departs from the right ventricle, but also an additional, so-called left artery, through which most of the blood is directed to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is a foramen of Panizza, which allows venous blood to enter the beginning of the systemic circulation - and vice versa.

In humans, this is an anomaly and is called birth defect hearts. The crocodile not only does not feel the defect here, but also has an additional mechanism that allows it to artificially pump oxygen-poor blood into the right artery. Or completely close the left artery, while his circulatory system will work almost the same as in mammals. The crocodile can control this so-called tooth valve at will.

The reasons that prompted nature to create such a remarkable mechanism have long occupied scientists. For a long time it was believed that the crocodile heart was a transitional stage on the way to the full-fledged four-chamber heart of warm-blooded mammals.

However, there was also an opposite point of view, according to which the crocodile is a descendant of a warm-blooded animal, which, for evolutionary reasons, became more profitable to live the life of a cold-blooded killer. In this case, the Panizza foramen and the serrated valve turn out to be an adaptation mechanism that allowed the transition to a cold-blooded existence. For example, in 2004, Roger Seymour from the Australian University of Adelaide and his colleagues showed that such a heart structure can be very useful for a semi-underwater lifestyle: a decrease in oxygen content in the blood can slow down the metabolism, which helps in long dives when a predator is motionless waiting for its kill. sacrifice.

Utah State University professor Colleen Farmer and her colleagues believe that thanks to this complex system a crocodile can quickly decompose pieces of prey it swallows.

But a crocodile cannot hesitate: if a fish, a monkey, or even a human leg is not digested too quickly, the reptile will die. Either in the mouth of another predator due to its clumsiness, or from hunger and intestinal upset: in a hot climate, bacteria multiply very quickly on a swallowed piece of meat in the belly of an animal.

Farmer believes that the point is not that the blood that has not passed through the lungs is poor in oxygen - to achieve such an effect, you do not need a complex heart device, but simply slow down your breathing. In her opinion, the fact is that this blood is rich in carbon dioxide. When a crocodile sends CO2-rich blood to the stomach and other digestive organs, special glands use it to produce gastric juice, and the more carbon dioxide they receive, the more active the secretion. It is known that in the intensity of secretion of gastric juice by their glands, crocodiles are ten times higher than the champions in this indicator among mammals. This allows not only to digest food, but also to suppress growth harmful bacteria in the stomach.

To prove their hypothesis, scientists first studied the state of the circulatory system during periods of forced fasting and during the digestion of food by the crocodile. It turned out that in a crocodile that had just eaten, for many hours the valve actually causes the blood to flow predominantly bypassing the lungs.

Next, the scientists surgically deactivated the valve, closing the entrance to the left aorta, in a group of young crocodiles. For the purity of the experiment, the control group was also operated on, but their aorta was not closed. As it turned out, after feeding in crocodiles whose left aorta was blocked, the production of gastric juice was significantly reduced - despite the fact that blood continued to flow to digestive organs in sufficient quantities through the right aorta. At the same time, the ability of crocodiles to decompose bones, which make up a significant part of their diet, also sharply decreased.

In addition to the function of transferring CO2 to the stomach, Farmer notes, the release of blood bypassing the lungs could also play another role important function, the presence of which will be the envy of many gym visitors.

For a crocodile, a rich meal almost always follows a dash for prey, during which the usually clumsy animal instantly jumps out of the water, grabs the prey that is ungainly at the watering hole and drags it under the water. At this time, such an amount of toxic lactic acid is generated in the muscles (it is because of them that after physical activity muscle aches), which can cause the death of the animal. According to scientists from Utah, this acid is also transported through the blood to the stomach, where it is utilized.

As for the foramen of Panizza, its role is not only to direct oxygen-poor blood to other organs, slowing down the crocodile’s metabolism, but also, on the contrary, to supply the digestive system with additional oxygen from the right aorta when needed. The toothed valve helps from time to time send blood rich in carbon dioxide not only to the stomach, but also to other internal organs who may need it.

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[[b]]Crocodiles (Crocodylia, or Loricata)[]

order of aquatic reptiles. The length of most crocodiles is 2-5 m, some - up to 6 m (salt crocodile, old males). The head is flat, with a long snout and a characteristically curved mouth, the body is flattened, the tail is powerful, paddle-shaped, compressed from the sides, the legs are massive and relatively short. The eyes have a vertically slit pupil and are located very high. The nostrils and ear openings are closed by valves.

The skin is thick, covered with large rectangular horny scutes on the upper and lower sides of the body and tail. Under the dorsal scutes, and in some species, under the ventral scutes, there are thick bony plates that form a carapace. The crocodile skull is characterized by the presence of two temporal arches and a fixed connection of the quadrate bone with the skull. The nasopharyngeal passage is separated from the oral cavity by the secondary bony palate. The same type of conical teeth sit in separate cells and are replaced as they wear out. The vertebrae are anterior concave. The ribs articulate with the vertebrae with a double head and have an uncinate process. There are "abdominal ribs". The shoulder girdle consists only of the scapula and coracoid.

In terms of brain development, crocodiles are superior to other reptiles. Of the sense organs, the organs of vision and hearing are especially well developed. The heart has 2 ventricles, completely separated by a septum (as in birds and mammals). At the intersection of the two aortic arches, there is an opening between them through which blood can flow from one arch to the other. Lungs are large, complex structure. The fleshy tongue is attached along its entire length to the bottom of the oral cavity. The stomach has thick muscular walls. There is no bladder. The cloaca is in the form of a longitudinal slit, in the rear part of which in males there is an unpaired genital organ, on either side of which lie musk glands. The same glands are present on the underside of the jaw.

Crocoids are common in all tropical countries; live in rivers, lakes and deep swamps; some live in the coastal part of the seas. They are active mainly at night. They feed mainly on fish, in addition to birds and mammals living near the water, as well as aquatic mollusks and crustaceans; at fords and watering places they attack large mammals(even for cattle). Large prey is dismembered on the shore using powerful jaws and forelimbs and swallowed in parts. The crocodile's voice is something between a bark and a roar, and is especially often heard during the breeding season.

The female lays her eggs in the sand in the shallows or buries them in a pile of rotting leaves of marsh plants. The number of eggs ranges from 20 to 100. The eggs have a dense white calcareous shell. Females of a number of species remain near the clutch for a long time, protecting the eggs and then the young from enemies. In some countries, during periods of drought, they bury themselves in the silt of drying up reservoirs and hibernate until the rains come. K. cause some damage to livestock. Large K. often attack humans. Crocodile meat is edible and consumed by the population of many tropical countries. Leather, especially alligator leather, is used for various products (briefcases, suitcases, saddles and the like).

The crocodile order includes 3 families: gharials, true crocodiles and alligators. Modern crocodiles are remnants large group crocodiles (descended in the Late Triassic from thecodonts), which included up to 15 families, uniting about 100 genera; most of them died out by the beginning of the Cenozoic. Fossil remains of crocodiles have been found in Europe, Asia, North and South America.