Nile crocodile how many chambers in the heart. Science: crocodile heart. The latest data from scientists

THE HEART OF THE KOBZAR The turquoise waters of the Baku Bay iron the ships along and across. Heavy transports slowly and solidly turn around; snow-white, like seagulls, passenger liners are easily sent to the exit to the open sea. Carefully moored to the berths low-sitting

A DOG'S HEART A few years ago, when so much was written about Stalin's crimes, and decency was on the rise, the national idea was also on the rise. But something prevented them from connecting. Remember when the SC passed the language law, the declaration of sovereignty and symbols,

A log floats on the river -
Oh, and it's wicked!
For those who fell into the river
Nose bit off...

(Crocodile.)

crocodiles

According to the general body structure, crocodiles resemble lizards in an enlarged form.

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

However, this is purely superficial. Crocodiles differ from lizards not only in size, but also in essential features of the anatomical structure. They are assigned to a special group.

The huge mouth of crocodiles is armed with sharp teeth, which do not adhere to the jaw bones, as in 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 in its structure approaches the more highly organized brain of birds. Lungs in 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 dressed in a horny cover that does not allow oxygen to pass through.

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

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 vital 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 the 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 a warm, tropical climate. Their life is closely connected with water bodies - on land they usually only bask and lay eggs, and they catch prey mainly in the water. Crocodiles are excellent swimmers and divers. Their long, muscular tail is laterally compressed and serves as a good mover, and the toes on the hind legs are partially interconnected 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 shields ossify, making the shell more durable.

Having plunged into the water, the crocodile sticks out of it only the upper part of the head, where its somewhat raised nostrils and eyes are placed. Recall that in the same way a flattened head and a frog puts out of the water, 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 the watering place and swim across the pond. 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.

Crocodiles belong to amphibious creatures, and have always been very frightening, interested in man. The most bloodthirsty reptile was deified at different times, but never remained indifferent to it. One of the topical issues that 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 the ancient Greek language, the word "crocodile" literally means "lizard", though much larger than other individuals.

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

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

Circulatory system

The heart of a crocodile, which will be discussed in this article, refers to the circulatory system. What structure does this organ have, how many chambers does it have, and how does the process of blood supply generally occur? So. The circulatory system of bloodthirsty reptiles is much more perfect 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 the general rule. 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 enters 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 heart of the crocodile has stopped on its path of 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

Famous American biologists for a long time 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 for several days, hiding in the water, waiting for its prey. When the victim is caught, the animal has to eat up to 25 kg of raw meat at a time. Well, what kind of digestive system should be in order to process, assimilate such an amount of food 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 circulatory system of the reptile is on the evolutionary path of development, and is approaching the warm-blooded human. Other scientific luminaries, on the contrary, rejected this hypothesis and considered the crocodile to be a true descendant of a warm-blooded creature, for which, for various reasons, it was more profitable to exist as a cold-blooded killer. The crocodile's heart chambers are not completely closed, for a person this fact threatens with a congenital defect, and the reptile feels great in this order of things.

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

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

As you can see, the structure of the circulatory system in 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?

1. The animal appeared in the world about 250 million years ago and first lived on land.
2. A real giant is recognized as a saltwater crocodile, which can be found on the shores of Fiji, on the Indian coast. Its length reaches seven meters, and the weight can reach up to a ton. And interestingly, female eggs are no larger than goose eggs.
3. A newly born baby crocodile is three times the size of its egg.
4. A 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 huge size, the animal can jump 2-3 meters ashore from the water when it comes to attacking the victim.
5. 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. Interestingly, teeth can be changed up to 100 times in a lifetime. And you can talk about the power of gripping the jaw of a crocodile for a very long time.
6. Predators eat rocks. Yes, you are not mistaken. They help them digest raw food. After all, the crocodile swallows food. Without chewing.
7. The male has his own harem, which can consist of 10 females. During the capture of a large victim, he can invite them for a joint absorption.
8. Crocodile blood contains a natural antibiotic that kills all pathogenic bacteria that enter 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.

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.

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