The heart of a crocodile is made up of The special structure of the crocodile's heart can help him in digestion. The external structure of the crocodile

Among the most dangerous predators in the world, crocodiles (the Latin name is Crocodilia) are in one of the first places - the only surviving heirs of dinosaurs that belong to the order of aquatic vertebrates. The average length of an adult is from 2 to 5.5 meters, and the mass of a crocodile can reach 550-600 kilograms.

The external structure of the crocodile

The structural features of crocodiles, both internal and external, help them survive in incredible conditions. It is interesting that, despite the long process of evolution, these reptiles retained almost all the features of their ancestors, in particular the body of a crocodile. , adapted to the aquatic environment:

Few people know that the integument of the body of a crocodile can have a different color, although, as a rule, the color of a crocodile is greenish-brown. The upper part of the skin is a series of extremely strong and tightly connected horny plates that grow with the individual itself, so that they do not shed. The color that the skin of a crocodile acquires can vary depending on external factors, or rather the ambient temperature. These animals are cold-blooded, so the normal body temperature of a crocodile varies from 30 to 35 degrees.

crocodile teeth

Often, representatives of this species are confused with alligators, although in reality they have a number of differences, the main of which is the location and structure of the dentition. For example, if the jaws of a crocodile are closed, then you can see the 4th tooth from the bottom, while in an alligator they are all closed. The total number of teeth in a crocodile is from 64 to 70, depending on the variety, and they have the same conical shape and a hollow inner surface where new incisors develop. On average, each fang of a crocodile changes every two years, and in a lifetime there can be up to 45-50 such updates. In turn, the tongue of the crocodile completely adheres to the lower jaw, so some people generally think that reptiles do not have this organ.

Despite the fact that the mouth of a crocodile looks very scary, in fact, its teeth are not adapted to chew food, so it swallows prey in large pieces. The digestive system of a crocodile has a number of specific features, for example, the stomach has a very large wall thickness, and to improve digestion, it contains stones (gastroliths). Their additional function is to change the center of gravity to improve swimming performance.

Features of the internal structure of crocodiles

In general, the internal structure of the crocodile is similar to the structure of other reptiles, but there are some unusual features. For example, the skeleton of a crocodile is very similar to the structure characteristic of dinosaurs: two temporal arches, a diapsid skull, and so on. Most of the vertebrae are in the tail (up to 37), while in the cervical region and trunk there are only 9 and 17, respectively. For additional protection, there are ribs in the abdominal part that are not connected to the spine.

The respiratory system of the crocodile is designed in such a way that the animal feels comfortable both on land and under water. The respiratory organs of the crocodile are represented by the choanae (nostrils), the nasopharyngeal passage with a secondary bony palate, the palatal curtain, the trachea, and the lungs with the diaphragm. The very powerful and complex lungs of a crocodile are capable of holding a large volume of air, while the animal can, if necessary, adjust the center of gravity. So that the crocodile's breathing does not prevent it from moving quickly, there are special muscles in the diaphragm area.

In its own way, the circulatory system of the crocodile is unique, which is much more perfect than that of other reptiles. So, the heart of a crocodile is four chambered (2 atria and 2 ventricles), and a special mechanism for mixing blood from arteries and veins makes it possible to regulate the process of blood supply. If you want to speed up the digestion process, then the structure of the crocodile heart allows you to change arterial blood to venous blood, which is more saturated with carbon dioxide and contributes to the production of additional gastric juice. It should also be noted that the blood of a crocodile has a high content of antibiotics, and hemoglobin is saturated with oxygen and works independently of red blood cells.

By the way, these predators do not have a bladder, and to search for a pair during the breeding season, there are special glands on the lower half of the jaw that emit a musky smell.

Their nervous system is very developed, in particular, the brain of a crocodile (or rather, the large hemispheres) is covered with a bark, and hearing and vision are especially developed from the organs of perception. We can say with confidence that the memory of the crocodile is very good, because he manages to memorize the paths along which other animals go to the watering place.

Answer from Lenzel[guru]
Not being able to chew prey with its powerful, but rather primitive jaws, the crocodile tears it into pieces in advance and sends it to the stomach in huge pieces.
The total mass of prey can be up to a fifth of the animal's own mass. Of course, these reptiles are far from their related pythons, but it’s quite difficult to imagine a person capable of peeling 15-20 kilograms of raw meat in one sitting, and even with bones.
The heart of a crocodile is four-chambered, 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 sent to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is an opening 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 congenital heart disease. The crocodile not only does not feel a vice 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. This so-called tooth valve can be controlled by the crocodile 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 heart of a crocodile is a transitional stage on the way to a full-fledged four-chambered heart of warm-blooded mammals.
However, there was an opposite point of view, according to which the crocodile is a descendant of a warm-blooded animal, which, for evolutionary reasons, has become more profitable to live the life of a cold-blooded killer. Such a structure of the heart can be very useful for a semi-submerged lifestyle: a decrease in the oxygen content in the blood can slow down the metabolism, which helps in long dives when a predator is motionless waiting for its prey. Thanks to such a complex system, the crocodile can quickly decompose the pieces of prey it has swallowed.

In her opinion, the fact is that this blood is rich in carbon dioxide. When the crocodile directs rich CO2 blood to the stomach and other digestive organs, special glands use it to produce gastric juice, and the more carbon dioxide enters them, the more active the secretion. It is known that in the intensity of secretion of gastric juice by their glands, crocodiles are ten times superior to champions in this indicator among mammals. This allows not only to digest food, but also to suppress the growth of harmful bacteria in the stomach.
And the crocodile cannot hesitate: if the fish, the monkey, and even the human leg, are not digested too quickly, the reptile will die. Either in the mouth of another predator due to its sluggishness, or from hunger and intestinal upset: in a hot climate, bacteria will multiply very quickly on a swallowed piece of meat in the belly of an animal. It turned out that in a crocodile that had just taken a bite for many hours, the valve actually caused blood to flow predominantly around the lungs. to enter the digestive organs in sufficient quantities through the right aorta. At the same time, the ability of crocodiles to decompose bones, which make up a large part of their diet, also sharply decreased. In a crocodile, a rich meal almost always follows a rush to prey, during which the usually clumsy animal instantly jumps out of the water, grabs the prey that gapes 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 the muscles ache after physical exertion), which can cause the death of the animal. According to scientists from Utah, with the blood, this acid is also transferred to the stomach, where it is utilized.

Answer from Victor richert[guru]
like everyone is warm

Answer from There is not[newbie]
cold and slippery

Answer from Marina K[guru]
Big and good! And so soulful! "Crocodile tears" is from experiences!

Answer from Andro gil[guru]
delicious00000

Answer from Photographer[guru]
Four-chamber

Answer from Natasha[guru]
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 sent to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is an opening 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 congenital heart disease. The crocodile not only does not feel a vice 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. This so-called tooth valve can be controlled by the crocodile 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 heart of a crocodile is a transitional stage on the way to a full-fledged four-chambered 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, for which, for evolutionary reasons, it became more profitable to live the life of a cold-blooded killer. In this case, the opening of Panizza and the notched valve are the adaptive mechanism that allowed the transition to a cold-blooded existence. For example, in 2004, Roger Seymour of the University of Adelaide in Australia showed with colleagues that such a structure of the heart can be very useful for a semi-submerged lifestyle: reducing the oxygen content in the blood can slow down the metabolism, which helps in long dives when a predator is motionless waiting for its sacrifice.

Researchers from the University of Chicago explained the structural features of the circulatory system of crocodiles. In experiments with American alligators, they were able to show that the ability to let venous blood bypass the lungs to body tissues is necessary for them to digest food. The work of scientists was published in the journal Physiological and Biochemical Zoology.

Crocodiles, like other reptiles, have preserved the right and left aortic arches. However, unlike other reptiles, the crocodile's heart is four-chambered, that is, it is divided into two atria and two ventricles.

The right aortic arch departs from the left ventricle, through which oxygenated blood, after circulation through the lungs, goes to tissues and organs. The left aortic arch departs from the right ventricle and carries venous blood containing little oxygen. At the exit from the heart, there is a partial mixing of venous and arterial blood from two aortic arches. The mixing of venous and arterial blood is characteristic of the imperfect circulatory systems of amphibians and reptiles.

However, crocodiles can "block" the connection between the aortic arches. In this case, venous blood from the left arch does not mix with arterial blood from the right. That is, the main blood circulation proceeds according to the pattern characteristic of mammals.

The left aortic arch leads to the stomach of the crocodile. When the junction of the arches is "overlapped", the venous blood flowing through the left arch goes directly there. Scientists were able to show that in the glands located in the stomach, reactions occur with the participation of carbon dioxide in the blood, as a result of which bicarbonate and acid are formed, which helps the crocodile digest the bones of its victims. The concentration of acid in the stomach of a crocodile during active digestion is more than ten times higher than the concentration characteristic of mammals.

Crocodiles are known for being able to digest huge amounts of food - up to a quarter of their own weight. If venous blood is artificially prevented from entering the stomach bypassing the lungs, the crocodile's digestion is disturbed, and it cannot cope with the digestion of its usual food.

Scientists put forward several assumptions that explain such a high concentration of acid. Firstly, the acid prevents the growth of bacteria, which is especially important, given that underdigested food is in the crocodile's stomach for quite a long time. Secondly, bicarbonate is necessary for crocodiles to neutralize the large amount of lactic acid that is formed in the muscles when attacking the victim. If the blood is not "cleansed" in time, a dose of lactic acid can be fatal. "Siding" helps crocodiles do this.

As a third possible reason, scientists cite the need to quickly secrete a large amount of acid. This is especially important for young crocodiles. Digestion proceeds better in warmth, and warm places are also attractive to natural enemies, of which there are many young animals that have not entered full strength. As soon as the crocodile gets into heat, he must begin to digest food, and for this he needs to quickly secrete a lot of acid, for which he uses the "overlapping" of the aortic arches.

Let me tell you a story that happened a few years ago. Now I am writing a school textbook of zoology according to the program, in which I participated myself. When this version of the program was just conceived, I convinced the ministerial worker that before a systematic study of individual groups, it was necessary to consider a fairly large topic, which would talk about animals in general.

"Okay, but where to start?" the official asked me. I said that the lifestyle of animals is determined primarily by what they eat and how they move. So, you need to start with a variety of ways to eat. “What are you talking about!” my interlocutor exclaimed. “How can I carry such a program to the minister? He will immediately ask why we inspire children that the most important thing is a gorge!”

I tried to argue. In general, the division of living organisms into kingdoms (animals, plants, fungi, and others) is associated primarily with the mode of nutrition, which, in turn, determines the features of their structure. Features 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 parts of them! Alas, my interlocutor was adamant. The minister will be primarily interested in the educational aspect of the program.

Thinking about how to organize the prologue differently, I then made an unforgivable mistake. My next idea was the proposal to start the study of the course of zoology with a variety of life cycles. When my interlocutor realized that as "the main thing in life" I was going to consider not food, but reproduction, he seems to have decided that I was mocking him ... In the end, I wrote something that, as I hoped, no one won't shock. Then the Methodists conjured over this program, who corrected everything they did not understand in it, and replaced the formulations with those that were in use in historical epochs when these same Methodists studied in pedagogical institutes. Then officials corrected the unfortunate program, then rethought it in the spirit of new guidelines, then ... - in general, I am writing a textbook on my "own" program and do not get tired of cursing.

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

Try to move your lower jaw: up and down, right and left, back and forth. Its "suspension" allows movement in all three planes! In addition, teeth sit on the jaws of mammals, the structure of which is determined by the task that is assigned to them - to pierce, crush, grind, cut, crush, bite off, tear, hold, gnaw, crush, pry, grind, scrape, etc. Our jaws are an evolutionary biomechanical masterpiece. Apart from mammals, almost no terrestrial vertebrates are capable of biting off food pieces! A few exceptions include the archaic tuatara, capable of sawing off the head of a petrel chick with its jaws, and turtles that have abandoned teeth in favor of a horny scissor-like beak. Both birds of prey and crocodiles do not bite off pieces of food, but simply tear them off - resting on 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 managed to learn something new about the functioning of the heart 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 time when the school was supposed to form a materialistic worldview, promoting evolution. Generally speaking, the fact of evolution has little to do with the "materialism-idealism" dilemma (refusing verbally from the mossy diamat, for some reason we still attach excessive importance to this dubious dichotomy). Alas, when some stale dogmas are taught instead of modern ideas about evolution, this only causes damage to the natural-scientific worldview. Among such dogmas is the linear idea of evolution. Think of the history of vertebrates as a "bush" of many branches, each of which went its own way, 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 has never tried to become a lizard, it lives its own life, and without taking into account this life (and the background of frogs) it is impossible to understand it!

What will the school teacher tell about crocodiles? He uses them to illustrate the assertion that the most progressive are animals with a four-chambered heart and "warm-bloodedness" (homeothermic). And look, kids! - the crocodile has a four-chambered heart, almost, almost like that of mammals and birds, only one extra hole remains. We see with our own eyes how the crocodile wanted to become a man, but did not reach it, stopped halfway.

So, the crocodile has a four-chambered heart. From its right half, the blood goes to the lungs, from the left - to the systemic circulation (to the consumer organs of the oxygen received in the lungs). But between the bases of the vessels departing from the heart there is a gap - the panizzi foramen. In the normal mode of operation of the heart, part of the arterial blood passes through this opening from the left half of the heart to the right half and enters the left aortic arch (look at the figure 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, feeding 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?

To begin with, let's figure out why two circles of blood circulation are needed at all. Fish manage with one thing: the heart - gills - consumer organs - the heart. Here the answer is clear. The lungs cannot withstand the pressure it takes to pump blood through the entire body. That is why the right (pulmonary) half of the heart is weaker than the left; that is why it seems to us that the heart is located on 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 in crocodiles through the right, "pulmonary" part of the heart and the left aortic arch? In humans, incomplete separation of blood flows can be caused by heart disease. Why such a "vice" crocodiles? The fact is that the heart of a crocodile is not an unfinished human heart, it is "conceived" more complicated and can function in two different modes! When the crocodile is active, both aortic arches carry arterial blood. But if the panizzian opening is closed (and crocodiles "know how" to do this), venous blood will go into the left aortic arch.

Traditionally, such a device is explained by the fact that it supposedly allows a crocodile hiding at the bottom to turn off the pulmonary circulation. In this case, venous blood is sent not to the lungs (which are still impossible to ventilate), but immediately to a 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, what good is it to circulate the blood?

American biologists figured out how to test the long-standing assumption that crocodiles transfer blood from one circle of blood circulation to another not in order to hide, but for the sake of better digestion of food (carbon dioxide is a substrate for the production of acid by the stomach glands). Researchers have seen that healthy young alligators in the process of digesting food through the left aortic arch (the one that supplies blood to the digestive system) flows venous, carbonic acid-rich blood. Then they began to interfere with the work of the heart of experimental crocodiles with surgical methods. In some of them, the transfer of venous blood to the left aortic arch was forcibly blocked; others underwent an operation simulating such an intervention. The effect was assessed by measuring the activity of gastric secretion and by X-ray observation of the digestion of bovine vertebrae swallowed by crocodiles. In addition, semiconductor sensors were placed in the unfortunate alligators, which made it possible 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 to the systemic circulation enhances the production of acid in the stomach and accelerates the digestion of food.

Crocodiles are able to feed 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 the prey quickly enough, they will simply get poisoned by it. The complicated 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-rays shows how solid bull vertebrae “melt” in acid in the stomachs of predators!

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

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

Crocodiles are vertebrate cold-blooded animals that lead a semi-aquatic lifestyle. Water is their favorite medium, being more constant in terms of temperature. It was thanks to her that the ancestors of crocodiles survived during the global cooling of the climate on Earth. The body shape of crocodile is lizard-shaped. The large head is flattened in the dorsal-abdominal direction, the muzzle is elongated or long, with strong elongated jaws, seated with sharp conical "fangs" up to 5 cm long, which grow throughout the life of the animal, replacing worn and broken ones. The teeth are strengthened in separate bone cells of the jaws, the base of the tooth is hollow inside; The bite of a crocodile is arranged in such a way that opposite the largest teeth of the lateral edge of one jaw are the smallest teeth of the other. This design was able to turn the dental apparatus into a perfect weapon for attack. In narrow-faced fish-eating gharials, the jaws can be compared to the jaws of tweezers, which allow them to grab small moving prey in the water with a lateral movement of the head.

The jaw system is arranged differently in Chinese alligators (Alligator sinensis), common in East China along the lower reaches of the Yangtze River. These are Small reptiles (maximum length 1.5 m), feeding mainly on bivalves, water snails, crustaceans, as well as frogs and slow-moving fish species. Grind such rough food closely planted posterior teeth with a flat surface of the crown. Rinsing their mouths in the water, the profited alligators get rid of fragments of crushed shells and shells.

At the end of the crocodile muzzle are bulging nostrils, the eyes are also raised and are located on the upper side of the head. This feature of the structure of the skull determines the favorite posture of the aquatic reptile: the body is blissful in the water - only the eyes and nostrils are visible from the outside.

Crocodiles have five fingers on their forelimbs, four on their hind limbs, they are connected by an interdigital swimming membrane. The tail is long, laterally compressed, very powerful and multifunctional: it is a “steering” and “engine” when swimming, a support when moving on land, and when hunting, it is like a stunning mace. During swimming, the limbs of crocodiles are laid back, the front ones are pressed to the sides, and the powerful flattened tail, bending, describes S-shaped movements. Lying in wait for large mammals at a watering hole, a huge combed crocodile (Crocodylus porosus) attacks suddenly, grabbing a zebra or antelope by the head and breaking its neck, or knocking the victim down with a terrible blow of the tail. During the breeding season, females tamp the "building material" brought for the nest with their tail, slap it on the water, spraying the nest with masonry.

The entire surface of the crocodile's body is covered with large, regular-shaped horny scales. The dorsal shields are thicker and bear convex, spiny ridges that merge into barbs on the tail. Each of the scales develops independently and grows at the expense of its underlying layers. Under the large shields of the skin on the back and tail, a real shell of bone plates, the osteoderm, develops. The shields are elastically connected to each other, due to which they do not restrict the movements of the animal. The shape and pattern of the shell surface is individual for each species. On the head, osteoderms fuse with the bones of the skull. Thus, the animal wears a real "armor" that effectively protects vital internal organs and the brain.

The structure of the skull is very unusual. The quadrate and articular bones are pierced by air-bearing outgrowths of the middle ear cavity. Most of the posterior bones of the skull contain cavities of a strongly overgrown and complexly branching system of the Eustachian tubes. The bones of the long muzzle and palate also contain significant voids: blind outgrowths of the nasal passage enter them. Scientists believe that the systems of air cavities and passages, penetrating almost the entire huge crocodile skull, significantly facilitate it, allowing you to keep your head above the surface of the water without significant expenditure of muscle energy (for silent and imperceptible immersion, it is enough for a crocodile to lower the pressure in the chest cavity and direct part of the air from the air cranial passages).

All species of crocodiles have highly organized sense organs. Unlike snakes, they hear perfectly - the range of auditory sensitivity is very large and is 100-4000 Hz. At the same time, crocodiles are deprived of Jacobson's special "snake" organ, which allows creepers to distinguish taste and smell with great accuracy. The eyes of crocodilians are adapted for night vision, but they serve well during the day. The retina of the eye contains mainly rod receptors that capture light photons. The pupil, like a cat's, is able to narrow in the light into a narrow vertical slit, and at night the alligator's eyes have a reddish-pink sheen, which is often taken as invariable evidence of its bloodthirstiness. It should be said that although the hunting instincts of crocodiles are aggravated at night, the ferocious predatory eyes are only a consequence of the anatomical structure of the visual analyzer. In the dark, the vertical pupil dilates, and the bloody color is provided by the presence in animals of a special pigment - rhodopsin - on the retina, illuminated by reflected light. Under water, the eyes of crocodiles are protected by a transparent nictitating membrane that closes them when immersed.

Everyone knows the expression "to shed crocodile tears." Indeed, crocodiles cry, but not from grief, pain or the desire to treacherously lull someone's vigilance. Thus, animals are freed from excess organic salts contained in the body. Their cloudy tears are unusually salty, but devoid of emotion. Salt glands are located in representatives of the family of real crocodiles, even under the tongue.

The respiratory system of crocodiles also has its own characteristics. The nostrils, like the external auditory openings, can be tightly closed by muscles - they automatically contract when the animal dives. The lungs have a complex structure compared to the baggy lungs of snakes and are able to accommodate a large supply of air. As a result, for example, a young Nile crocodile only 1 meter long is able to stay under water for about 40 minutes, and without the slightest harm to its own health. As for large adults, the duration of their “diving” can reach 1.5 hours. It should be noted that scaly reptiles are not able to absorb oxygen through rough skin, as thin-skinned amphibians (frogs, newts) do.

The air inhaled through the nostrils passes through the paired nasal passages, separated from the oral cavity by a secondary bony palate, which serves as a kind of protection of the skull from the inside. In the case when a crocodile tries to swallow a large and severely mutilated victim, bone fragments and desperate resistance, jerks and blows of the doomed animal are not able to injure the vault of the oral cavity and damage the brain. In front of the choanas (internal nostrils), a muscular veil descends from above, which is pressed against a similar outgrowth at the base of the tongue and forms a valve that completely separates the oral cavity from the respiratory tract. Thus, due to its anatomical structure, the crocodile is able to drown, tear and swallow prey without the risk of choking itself.

The mechanism of ventilation of the lungs is peculiar and unusual in crocodiles. If for most higher vertebrates a change in the volume of the chest is produced by the movement of the ribs, then the volume of the lungs in crocodiles also changes with the movement of the liver. The latter is moved forward by contraction of the transverse abdominal muscles, causing an increase in pressure in the lungs and exhalation, and then moves backward by the longitudinal diaphragmatic muscles that connect the liver with the pelvis, causing a decrease in pressure in the lungs and, accordingly, inspiration. As researchers K. Hans and B. Clark proved, in crocodiles in water, it is the movements of the liver that play the main role in lung ventilation.

The heart of crocodiles consists of four chambers and is much more perfect than the three-chambered heart of other reptiles: oxygen-enriched arterial blood does not mix with venous blood, which has already given oxygen to organs and tissues. The heart of crocodiles differs from the four-chambered heart of mammals in that the latter retains two aortic arches with an anastomosis (bridge) at the intersection. Thus, despite the fact that the body temperature, metabolic rate, motor activity and appetite of crocodiles significantly depend on the ambient temperature, the process of gas exchange in their cells proceeds more efficiently than in lizards and turtles.

The digestive system of crocodiles is distinguished primarily by the absence of saliva in the oral cavity. In addition, there is another amazing adaptation: in the thick-walled muscular stomach of most adult crocodiles there is a certain amount of stones (the so-called gastroliths), which the animals deliberately swallow. In Nile crocodiles, the weight of stones in the stomach reaches 5 kg. The role of this phenomenon is not entirely clear; it is assumed that the stones play the role of ballast and move the center of gravity of the crocodile down in front, giving greater stability when swimming and facilitating diving, or they contribute to grinding food while contracting the walls of the stomach, as in birds.

Crocodiles do not have a bladder, which is apparently associated with life in the water. Urine is excreted along with feces through a special organ that removes waste products located on the ventral side of the animal (it is called the cloaca). The cloaca has the form of a longitudinal slit, while in lizards and turtles it is of a transverse type. In the back of it, males have an unpaired genital organ. The female lays fertilized eggs, protected from the outside by a dense calcareous shell, and from the inside by primary food and moisture supplies sufficient for the development of the embryo.

On the sides of the cloaca, as well as under the lower jaw of crocodiles, there are large paired glands that secrete a brown secret with a strong smell of musk. The secretion of these glands is especially activated during the breeding season, helping sexual partners find each other.