The internal structure of turtles. Circulatory systems of vertebrates (difficult). Turtles: who are they

03.11.2019

The cardiovascular system of turtles

The cardiovascular system is typical for reptiles: the heart is three-chambered, large arteries and veins are connected. The amount of under-oxidized blood entering the systemic circulation increases with increasing external pressure (for example, when diving). In this case, the heart rate decreases, despite the increase in the concentration of carbon dioxide.

The heart consists of two atria (left and right) and a ventricle with an incomplete septum. The atria communicate with the ventricle through a bifid canal. A partial interventricular septum develops in the ventricle, due to which a difference in the amount of oxygen in the blood is established around it.

From the right part of the ventricle, containing venous blood, the pulmonary artery departs, from the middle of the ventricle (where the blood is mixed) - the left aortic arch, from the left part of the ventricle (containing arterial blood) - the right aortic arch.

The right and left aortic arches bypass the esophagus and, converging on the dorsal side of the body, form the dorsal aorta, which runs backward along the spine. The dorsal aorta contains mixed blood.

After contraction of the right and left atria, oxygen-rich arterial blood enters the upper ventricle and forces venous blood into the lower half of the ventricle. Mixed blood appears in the right side of the ventricle. Thus, arterial blood from the upper half of the ventricle enters the right aortic arch, which carries blood to the brain; venous blood from the lower half to the pulmonary artery, and mixed blood from the right side of the ventricle to the left aortic arch, which carries blood to the body. The right and left aortic arches curve back around the esophagus, and merge into a single dorsal aorta, the branches of which carry blood to all organs. From the right aortic arch, the carotid arteries branch off with a common trunk, from the left aortic arch, the subclavian arteries depart, carrying blood to the forelimbs.

The three-chambered heart of turtles gives a weak sound signal during contractions.
In turtles, the topography and branching of the vessels are greatly altered. An important feature of reptiles is the presence of the portal system of the kidneys. Venous blood from the posterior third of the body first passes through the kidneys and only then enters the posterior vena cava and heart. In this regard, all fast-acting and nephrotoxic drugs should be administered in the upper body.

Heart rate (HR) depends on the ambient temperature, species, age and weight of the turtle.

Lymphatic (circulatory) system

In reptiles, the lymphatic system is much better developed than the venous system. There is a superficial and deep lymphatic network, from where the lymph is collected into the intercellular spaces. Turtles do not have true lymph nodes. Instead, plexiform lymphatic structures (clumps of lymphatic capillaries and lymphoid tissue) develop.
The number of lymphocytes decreases sharply in the cold season, due to a drop in the immune status and the production of antibodies.

Scheme below:

A - arterial system;
B - venous system. (White color shows arteries with arterial blood, dots - with mixed blood and black - arteries and veins with venous blood):

1 - right atrium, 2 - left atrium, 3 - ventricle, 4 - right aortic arch, 5 - left aortic arch,
6 - common carotid artery, 7 - subclavian artery, 8 - fusion of the right and left aortic arches into the dorsal aorta,
9 - dorsal aorta, 10 - arteries leading to the stomach and intestines, 11 - renal arteries, 12 - iliac artery,
13 - sciatic artery, 14 - tail artery, 15 - pulmonary artery, 16 - jugular vein,
17 - external jugular vein, 18 - subclavian vein, 19 - right anterior vena cava,
20 - tail vein, 21 - sciatic vein, 22 - iliac vein, 23 - portal vein of the kidney,
24 - abdominal vein, 25 - anterior abdominal vein, 26 - veins coming from the stomach and intestines,
27 - posterior vena cava, 28 - hepatic vein, 29 - pulmonary vein, 30 - lung, 31 - kidney, 32 - liver.

The heart (cor) is located in the anterior part of the abdominal cavity. It consists of three sections: two atria (atrium dexter et atrium sinister; Fig. 1 (1, 2) and one ventricle (ventriculus; Fig. 1 (3)). The ventricular cavity is divided by an incomplete septum into two communicating chambers: the dorsal (dorsal ) and abdominal (ventral). When the ventricle contracts, this septum completely separates the chambers for a short time. Both atria open into the dorsal chamber of the ventricle, but the opening of the left atrium is located to the left, closer to the blind end of this chamber, and the opening of the right atrium is closer to the free edge Due to this arrangement, during atrial contraction, arterial blood coming from the left atrium accumulates in the left side of the dorsal chamber of the ventricle, venous blood - mainly in its ventral chamber, and the right side of the dorsal chamber of the ventricle is filled with mixed blood.

The arterial cone in turtles, like in other reptiles, is completely reduced. The remaining three main arterial trunks - the pulmonary artery and two aortic arches - begin in the ventricle of the heart on their own. The pulmonary artery (arteria pulmonalis; Fig. 1 (15)) begins with one trunk in the ventral (venous) part of the ventricle. Upon exiting the heart, the common trunk divides into the right and left pulmonary arteries, which carry venous blood to the right and left lungs, respectively. The pulmonary artery of each side is connected by a short thin ductus botallii to the corresponding aortic arch (not shown in the diagram). Through the ductus arteriosus, a small amount of blood from the pulmonary arteries can drain into the aortic arches, reducing blood pressure in the lungs during prolonged exposure to water. In tortoises, the botallian ducts usually become overgrown, turning into thin bundles.

In the lungs, venous blood gives off carbon dioxide and is saturated with oxygen. Arterial blood from the lungs is sent to the heart through the pulmonary veins (vena pulmcnalis; Fig. 1 (29), which unite before flowing into the heart into a common unpaired trunk, which opens into the left atrium. The described vascular system makes up a small or pulmonary, circulatory circle. Greater circle blood circulation begins with the aortic arches.The right aortic arch (arcus aortae dexter; Fig. 1 (4)) departs from the left side of the dorsal chamber of the ventricle - it receives mainly arterial blood.The left aortic arch (arcus aortae sinister; Fig. 1 (5)) departs somewhat to the right, in the region of the free edge of the interventricular septum - arterial blood mixed with venous blood enters this vessel.

From the right aortic arch immediately after it leaves the heart, either a short common trunk (anonymous artery a. innominata), or independently four large arteries - the right and left common carotid arteries (arteria carotis communis; Fig. 1 (6)) and the right and left subclavian (arteria subclavia; Fig. 1 (7)). Before entering the skull, each of the common carotid arteries is divided into internal and external carotid arteries (a. carotis interna et a. carotis externa); they are not shown on the diagram. The blood goes to the head through the carotid arteries, and to the forelimbs through the subclavian arteries. Since these arteries depart from the right aortic arch, the head and forelimbs receive the most oxygenated blood. In the region where the arteries originate from the right aortic arch lies a compact formation - the thyroid gland (glandula thyreoidea).

Having rounded the heart, the right and left aortic arches under the spinal column merge into an unpaired dorsal aorta (aorta dorsalis; Fig. 1 (8, 9)). Just before the confluence into the dorsal aorta, from the left aortic arch, either a short common trunk, or three large arteries (Fig. 1 (10)), supplying blood to the stomach (arteria gastrica and intestines (arteria coeliaca et arteria mesenterica)). the aorta separates the branches to the sex glands and kidneys (arteria renalis), then the paired iliac arteries (arteria iliaca; Fig. 1 (12)) and the paired sciatic arteries (arteria ischiadicas; Fig. Fig. 1 (13)), supplying blood to the pelvic area and hind limbs, and in the form of a thin tail artery (arteria caudalis; Fig. 1 (14)) goes into the tail.

Venous blood from the head is collected in large paired jugular veins (vena jugularis dextra et sinistra; Fig. 1 (16)), passing along the sides of the neck parallel to the common carotid arteries. Thin external jugular vein (vena jugularis externa; Fig. 1 (17)) stretches next to the right jugular vein and then merges with it. Each of the subclavian veins (vena subclavia; Fig. 1 (18)) coming from the forelimbs merges with the corresponding jugular vein, forming the right and left anterior vena cava (vena cava anterior dextra et vena cava anterior sinistra; Fig. 1 (19)) flowing into the right atrium (more precisely, into the venous sinus, but it is even less developed in turtles than in other reptiles).

From the back half of the body, venous blood enters the heart in two ways: through the portal system of the kidneys and through the portal system of the liver. From both portal systems, blood is collected in the posterior vena cava (vena cava posterior; Fig. 1 (27)). The tail vein (vena caudalis; Fig. 1 (20)) enters the pelvic cavity and bifurcates. The branches of the tail vein merge on each side with the sciatic (vena ischiadica; Fig. 1 (21)) and iliac (vena iliaca; Fig. 1 (22)) veins coming from the hind limbs. Immediately after the fusion, there is a division into the abdominal vein (v abdominalis; Fig. 1 (24)), which carries blood to the liver, and the short portal vein of the kidneys (vena porta renalis, Fig. 1 (23)), which enters the corresponding kidney, breaking up there on the capillaries. The renal capillaries gradually merge into the efferent veins of the kidneys. The efferent veins of the right and left kidneys merge into the posterior vena cava (vena cava posterior; Fig. 1 (27)), which passes through the liver (but the blood from it does not enter the hepatic capillaries!) And flows into the right atrium.

Part of the venous blood from the pelvic region, as mentioned above, enters the paired abdominal veins (vena abdominalis; Fig. 1 (24)). Anterior to the girdle of the forelimbs are thinner anterior abdominal veins (vena abdominalis anterior; Fig. 1 (25)), merging with the abdominal veins. At the confluence between the right and left abdominal veins, an anastomosis (bridge) is formed, and they go to the liver, breaking up there into capillaries - they form the portal system of the liver. Blood from the stomach and intestines through the vein system (Fig. 1 (26)) also enters the liver and diverges through the hepatic capillaries. The hepatic capillaries merge into short hepatic veins (vena hepatica; Fig. 1 (28)), which, inside the liver, join the posterior vena cava.

Fish

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

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

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

Lungfish

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

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

Amphibians

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

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

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

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

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

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

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

4) In lower amphibians (tailed and legless) amphibians

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

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

reptiles

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

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

crocodiles

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

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

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

Birds and mammals

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

Fruit

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

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

testiki

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

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

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

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

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

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

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

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

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

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

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

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

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

The distinctive features of the Turtle squad (TESTUDINES) are as follows:

The body is enclosed in a bony shell, covered on top with horny scutes or skin (in the Far East). The head on a long movable neck, like the legs, can usually be retracted under the shell. There are no teeth, but the jaws have sharp horny edges. Eggs with hard calcareous shells.

Turtle skin

Turtle skin is made up of two main layers: the epidermis and the dermis. The epidermis completely covers the entire surface of the body, including the shell. In turtles, molting occurs gradually and the epidermis changes in separate areas as it wears out. In this case, a new stratum corneum is formed, which lies under the old one. Between them, lymph begins to flow and sweat fibrin-like proteins. Then lytic processes increase, which leads to the formation of a cavity between the old and new stratum corneum and their separation. In land turtles, only the skin normally sheds. Large shields on the head, paws and shell shields should not shed.

The head is located on a long movable neck and can usually be retracted under the shell in whole or in part, or placed sideways under the shell. The roof of the cranium does not have temporal pits and zygomatic arches, that is, it belongs to the anapsid type. The large eye sockets are separated along the midline by a thin interorbital septum. Behind the ear notch protrudes into the roof of the skull.

A thick, fleshy tongue is placed in the turtle's mouth.

The cardiovascular system of turtles

An unpaired thyroid gland is located in front of the goiter. Its hormones play a very important role in the regulation of general tissue metabolism, affect the development of the nervous system and behavior, the functions of the reproductive system and growth progress. In turtles, thyroid function increases during wintering. The thyroid gland also produces the hormone calcitonin, which slows down the resorption (absorption) of calcium from bone tissue.

All turtles breathe through their nostrils. Open mouth breathing is not normal.

The external nostrils are located at the front end of the head and look like small rounded holes.

The internal nostrils (choanas) are larger and oval in shape. They are located in the anterior third of the sky. When the mouth is closed, the choanae are closely adjacent to the laryngeal fissure. At rest, the laryngeal fissure is closed and opens only during inhalation and exhalation with the help of a dilator muscle. The short trachea is formed by closed cartilaginous rings and at its base is divided into two bronchi. This allows turtles to breathe with their heads retracted inward.

Digestive system of turtles

Most land turtles are herbivorous, most aquatic turtles are carnivores, and secondarily terrestrial turtles are omnivores. Exceptions occur in all groups.

All modern turtles have fully reduced teeth. The upper and lower jaws are covered with horn covers - ramphoteks. In addition to them, the front paws can participate in grinding and fixing the feed.

Vision turtles

The main structure of the eye is an almost spherical eyeball located in the deepening of the skull - the eye socket and connected to the brain by the optic nerve. It departs from the inside of the eyeball and is enclosed in a case. Accommodation of the lens is carried out by contraction of the ciliary muscle, which in turtles is striated, and not smooth as in mammals.

The structure of a turtle is very complex. This knowledge can be useful when keeping these reptiles at home. We will begin, perhaps, an excursion into the anatomy of turtles from the axial skeleton, namely the spine.

Spine

It has a cervical, thoracic, lumbar, sacral and caudal region. Cervical, has eight vertebrae in its composition, several anterior ones are connected to form a movable joint. The vertebrae of the body are connected to the ribs. The upper vertebrae, together with the sternum, actually form the chest and cavity, which contains important internal organs. The pelvic bones are attached to the sacral vertebrae. The caudal vertebrae are presented in large numbers, they do not carry a special functional load on themselves. The skull of a turtle is represented by a large number of bones. It has two sections of the brain and visceral.

The eyes are located on the side of the head, looking down. These animals eat with the help of a hard beak, which has bumps similar to teeth. The turtle's head has a rather streamlined shape, which lends speed to marine species.

The tortoise brain has two sections, head and dorsal. Despite the fact that the brain is very small. Most of the functional load is carried by the spinal cord.

shell

The structure of the tortoise shell has a number of features that are unique to this amphibian. The shell is a distinctive feature of this amphibian from all other species that inhabit our planet. It also serves as protection for reptiles. Shell functions:

Injury protection;
Preservation of heat produced by the body;
Protection of internal organs, axial skeleton.

This structure is very strong, supporting a mass far greater than the weight of the turtle. Shell components:

Carapace - dorsal shield;
Plastron - abdominal shield.

The carapace is represented by many bone plates that are firmly connected to the ribs and vertebrae. It consists of half a stone, bone plates. The lower shield is formed by ribs. Between themselves, these two shields are connected with the help of ligaments or motionless bone structures. At the top of the shell there are horny shields. There are seams between the shields and plates, but they go in different directions, this gives reinforcement to the frame. In front and behind the shields have holes for the limbs, which, in case of danger, the animal can hide inside. The shell of different types of turtles has a different shape in structure. These distinctive features appeared in the process of evolution. They are an adaptive mechanism associated with the living conditions of the reptile.

Bone plates, scutes tend to grow throughout the life of the animal. The intensity of growth is associated with climatic conditions, in warm weather they grow faster. Keratin deposited in the plates gives them an annular shape. Scientists from these formations can judge the age of the reptile, its health, the presence of diseases, and whether it was kept in captivity.

Young turtles have very large distances between the plates. With intensive growth, the plates grow towards each other, thereby forming a different number of seams.

Leather

The skin has two layers, the epidermis and the dermis itself. The epidermis covers the entire surface of the turtle's body, as it ages, it peels off, the animal molts. The skin is very strong, elastic, not having glands in its composition. Moisture does not evaporate through it, so if a marine life gets on land, the skin will not dry out. But it is able to absorb warm liquid. With this mechanism, the animal controls the balance of water in the body.

claws

Claws come from the epidermis. On the paws they have five fingers, respectively, at the distal end there is a claw. Their number may vary, depending on the type of turtle. At home, it is imperative to take care of them in time, cut or file. With untimely care, a circulatory network is formed inside them, which is then injured, bleeding occurs. Claws grow slowly, their rapid growth indicates pathology. Requires expert advice.

The cardiovascular system

The circulatory system forms two closed circles. The heart has three chambers, consisting of two atria and one ventricle, which has an incomplete septum. The right side of the ventricle contains venous blood, it gives it to the pulmonary artery. The middle part, containing mixed blood, leaves the left side of the aortic arch. The left side of the ventricle carries pure arterial blood through the right side of the aorta. Both arches communicate with one aorta, which makes an internal turn around the food tube. The descending aorta carries arteriovenous blood. How is blood enriched with oxygen? Venous blood through the pulmonary arteries enters the lungs, where it exchanges carbon dioxide, and is itself enriched with oxygen and turns into arterial blood. Through the pulmonary veins, it returns to the heart, flowing into it through the left atrium.

Very important arterial trunks supplying the brain, spinal cord and upper limbs of turtles depart from the aorta. These are the carotid and subclavian arteries. The descending part of the aorta gives many branches supplying the internal organs, the stomach, the entire intestinal tract, the sex glands and the lower limbs.

Blood from the head departs through the jugular veins, previously gathering in the sinuses. The jugular veins are paired and flow into the vena cava, this is the main vein that collects the venous blood of all organs. It enters the right atrium. The entire cardiovascular system of this reptile is very similar to other amphibians.

Offspring

These reptiles lay eggs. Animals do not incubate them, but lay them in a secluded sunny place. Under the sun, the process of maturation of babies takes place. To break through a strong shell, babies have a growth on their head, with which they make their way out. This growth is rudimentary. In appearance, these reptiles are an exact copy of adults, only hundreds of times smaller. Already from birth, they are independent, looking for their own food.

Respiratory system

The upper respiratory tract, and in general the entire respiratory system, begins with the nostrils, which carry the incoming air to the choanae. From the choanae, air is thrown into the mouth, its further movement along the larynx. The body of the larynx has three cartilages. After the larynx comes the trachea, which consists of half rings giving it a round shape. Further, this tube is divided into the right and left bronchus, which flow into the lungs. The chest of these animals is motionless, therefore the respiratory act is carried out only with the help of the expansion of the lungs themselves. Accessory muscles help them do this. The volume of lung tissue is quite large, which allows turtles to stay under water for a long time.

digestive tract

Through the oral cavity, food enters the wide esophagus, which smoothly passes into the stomach. On the left side of the stomach is the spleen, which produces various elements of the blood. Further, the stomach continues with a horseshoe-shaped duodenum, which, as it were, envelops the pancreas. The pancreas is an organ that produces enzymes necessary for the process of digestion of food. The small intestine passes into the large intestine, which ends in a cloaca. It is located on the outside of the tail. Their gastrointestinal tract is quite long. This is necessary for a longer digestion of consumed plant foods. Also, the digestive organs include the liver and gallbladder, the duct of which opens in the thickness of the duodenum.

urinary system

Turtles have kidneys as an organ for the formation and excretion of urine. The kidneys are represented by a paired organ located above the pelvic cavity closer to the upper shield. The ureters exit from the kidneys and open into the cloaca.

The genital organs are represented by the testes, the vas deferens, which also open on the cloaca. The mating organ is hidden in the cloaca.

The reproductive organs of females are represented by the ovaries, which do not communicate with the oviducts. The oviduct opens on the anterior abdominal wall with a large funnel. Eggs, when mature, fall into the body cavity, and then move along the oviduct to the exit.

The tortoise can never leave its shell, because it has grown together with it;
The cervical vertebrae are so elastic that they allow you to rotate your head, stick it out or hide it in moments of danger;
The reptile is able to completely hide all parts of the body inside the shell;
The shell, although it is a defense, can also be damaged;
The turtles were in orbit, from where they returned alive;
They do not have vocal cords, but are able to make sounds, this happens by quickly squeezing out the air flow;
The glands present in the cloaca secrete pheromones that the male is able to hear at a distance of several kilometers;
Good blood supply to the cloaca allows gas exchange through it;
These reptiles can live up to hundreds of years;
Not all of these animals are herbivores, they can even eat their own kind, killing them with a massive beak and tearing them apart with powerful paws.

The turtle has a very interesting structure of its body. Her body has nothing superfluous, all formations perform a certain function. More detailed information about the structure of the turtle body can be found by reading the special literature. By the way, you can buy it in bookstores. Studying the structure of reptiles helps to better understand its habits, food preferences. Create the most favorable conditions for their maintenance.

The tortoise is an animal of the chordate type, reptile class, order of the turtle (Testudines). These animals have existed on planet Earth for over 220 million years.

The turtle received its Latin name from the word "testa", meaning "brick", "tile" or "clay vessel". The Russian analogue comes from the Proto-Slavic word čerpaxa, which in turn comes from the modified Old Slavic word "čerpъ", "shard".

Turtle - description, characteristics and photos

turtle shell

A characteristic feature of turtles is the presence of a shell, which is designed to protect the animal from natural enemies. turtle shell consists of dorsal (carapace) and ventral (plastron) parts. The strength of this protective cover is such that it easily withstands a load exceeding the weight of a turtle by 200 times. The carapace consists of two parts: an inner armor made of bone plates, and an outer one made of horny shields. In some species of turtles, the bone plates are covered with dense skin. The plastron was formed thanks to the fused and ossified sternum, clavicles and abdominal ribs.

Depending on the species, the size and weight of the turtle vary significantly.

Among these animals there are giants weighing more than 900 kg with a carapace size of 2.5 meters or more, but there are small turtles whose body weight does not exceed 125 grams, and the shell length is only 9.7-10 cm.

Turtle head and eyes

turtle head has a streamlined shape and medium size, which allows you to quickly hide it inside a safe haven. However, there are species with large heads that do not fit well or not at all in the shell. In some representatives of the genus, the tip of the muzzle looks like a kind of "proboscis" ending in nostrils.

Due to the peculiarities of the way of life on land, the eyes of the turtle look at the ground. In water representatives of the detachment, they are located closer to the crown and are directed forward and upward.

The neck of most turtles is short, however, in some species it can be comparable to the length of the carapace.

Do turtles have teeth? How many teeth does a turtle have?

To bite off and grind food, turtles use a hard and powerful beak, the surface of which is covered with rough bumps that replace teeth. Depending on the type of food, they can be razor-sharp (in predators) or with jagged edges (in herbivores). The ancient turtles that lived 200 million years ago, unlike modern individuals, had real teeth. The tongue of turtles is short and serves only for swallowing, not for capturing food, so it does not protrude.

Limbs and tail of turtles

A turtle has 4 legs in total. The structure and functions of the limbs depend on the lifestyle of the animal. Species that live on land have flattened forelimbs adapted for digging soil, and powerful hind legs. Freshwater turtles are characterized by the presence of leathery membranes between the toes on all four paws that facilitate swimming. In sea turtles, the limbs in the process of evolution were transformed into peculiar flippers, and the size of the front ones is much larger than the back ones.

Almost all turtles have a tail, which, like the head, is hidden inside the shell. In some species, it ends in a nail-like or pointed spike.

Turtles have well-developed color vision, which helps them in finding food, and excellent hearing, which allows them to hear enemies at a considerable distance.

Turtles molt, as do many reptiles. In land species, molting affects the skin in a small amount; in aquatic turtles, molting occurs imperceptibly.

During molting, transparent shields peel off from the shell, and the skin from the paws and neck comes off in tatters.

The life expectancy of a turtle in natural conditions can reach 180-250 years. With the onset of winter cold or summer drought, turtles go into hibernation, the duration of which can exceed six months.

Due to the weakly expressed sexual characteristics of turtles, it is very difficult to determine which of the animals is a “boy” and which is a “girl”. Nevertheless, if you approach the issue with care, having studied some of the external and behavioral characteristics of these exotic and interesting reptiles, then finding out their gender will not seem so difficult.

shell

In the female, it usually has a more elongated, elongated shape compared to the male.

Plastron (lower shell)

Turn the turtle over and look at it carefully - the shell from the side of the abdomen closer to the anus in female turtles is flat, in males it is slightly concave (by the way, this nuance facilitates the mating process).

Tail

In male turtles, the tail is slightly longer, wider and thicker at the base, most often bent down. The tail of the "ladies" is short and straight.

anal opening (cloaca)

In females, it is somewhat closer to the tip of the tail, shaped like an asterisk or a circle compressed on the sides. In male turtles, the anus is narrow, oblong, or slit-shaped.

claws

In almost all species, except for the leopard tortoise, the claws of males on the forelimbs are longer than those of females.

notch at the tail

Male turtles have a V-shaped notch at the back of the shell, which is necessary for mating turtles.

Behavior

Male turtles are most often more active, and during the mating season they are distinguished by their aggressiveness towards the rival and the “lady of the heart”, they chase her, trying to bite, and nod their heads in a funny way. The female at this time can calmly observe the "courtship", hiding her head in the shell.

Some species of turtles have specific differences between females and males, such as color, size, or head shape.

Types of turtles - photo and description

The turtle squad consists of two suborders, divided by the way the animal puts its head into the shell:

Hidden neck turtles, folding the neck in the form of the Latin letter "S";
Side-necked turtles, hiding their heads towards one of the front paws.

According to the habitat of turtles, there is the following classification:

Sea turtles (live in the seas and oceans)
Land turtles (live on land or in fresh water)
- Land turtles
- freshwater turtles

In total, there are more than 328 species of turtles, forming 14 families.

Varieties of land turtles

Galapagos tortoise (elephant) (Chelonoidis elephantopus)

The length of the shell of these turtles can reach 1.9 meters, and the weight of the turtle can exceed 400 kg. The size of the animal and the shape of the shell depend on the climate. In arid regions, the carapace is saddle-shaped, and the limbs of the reptile are long and thin. The weight of large males rarely exceeds 50 kg. In a humid climate, the shape of the dorsal carapace becomes domed, and the size of the animal increases significantly. The elephant tortoise lives in the Galapagos Islands.

Egyptian tortoise (Testudo kleinmanni)

small representative of land turtles. The size of the carapace of males barely reaches 10 cm, females are slightly larger. The color of the shell of this species of turtles is brownish-yellow with a small border along the edges of the horny scutes. The Egyptian tortoise lives in northern Africa and the Middle East.

Central Asian tortoise (Testudo (Agrionemys) horsfieldii)

a small reptile with a shell size up to 20 cm. The carapace has a rounded shape and is colored in yellowish-brown tones with darker spots of an indefinite shape. On the front limbs, these turtles have 4 fingers. The most popular type of turtle for home keeping, lives about 40-50 years. It lives in Kyrgyzstan, Uzbekistan, Tajikistan, Afghanistan, Lebanon, Syria, northeastern Iran, northwestern Pakistan and India.

leopard turtle (panther turtle) (Geochelone pardalis)

The length of the carapace of this turtle exceeds 0.7 m, and the weight can reach 50 kg. The shell of this species of turtles is high and has a domed shape. Its coloration has sandy-yellow tones, in which young individuals clearly show a spotted pattern of black or dark brown, which disappears as they grow older. This type of turtle lives in Africa.

Cape spotted turtle ( Homopus Signatus)

world's smallest turtle. The length of her carapace does not exceed 10 cm, and the weight reaches 95-165 grams. Lives in South Africa and southern Namibia.

Types of freshwater turtles

Painted turtle (decorated turtle) (Chrysemys picta)

A rather small species of turtles with individual sizes from 10 to 25 cm. The upper part of the oval dorsal shell has a smooth surface, and its color can be either olive green or black. The skin has the same color but with different stripes of red or yellow tone. They have leathery membranes between their toes. Lives in Canada and the USA.

European bog turtle (Emys orbicularis)

The size of individuals can reach up to 35 cm, and weight 1.5 kg. The smooth, oval carapace is movably connected to the plastron and has a slightly convex shape. Representatives of this species have a very long tail (up to 20 cm). The color of the upper shell is brown or olive. The color of the skin is dark with yellow spots. The turtle lives in Europe, the Caucasus, and Asia.

Red-eared turtle (yellow-bellied turtle) (Trachemys scripta)

The shell of these turtles can be up to 30 cm long. Its bright green coloring in young individuals eventually turns into yellow-brown or olive. Near the eyes on the head there are two spots of yellow, orange or red. This feature gave the species its name. lives in the USA, Canada, in the north-west of South America (in the north of Venezuela and Colombia).

Cayman turtle (biting) (Chelydra serpentina)

A characteristic feature of the turtle is a cruciform plastron and a long tail, which is covered with scales with small spikes, as well as the skin of the head and neck. The size of the shell of these turtles can reach 35 cm, and the weight of an adult animal is 30 kg. The caiman tortoise waits out unfavorable conditions in hibernation. This turtle lives in the USA and in the southeast of Canada.

Sea turtle species

Turtle hawksbill (true carriage) (Eretmochelys imbricata)

The carapace of these turtles has the shape of a heart up to 0.9 m in size. The upper layer of the shell is painted in brown tones with a pattern in the form of multi-colored spots. In young individuals, the horny plates overlap each other like tiles, but as it grows, the overlap disappears. The front flippers of the animal are equipped with two claws. The hawksbill lives both in the latitudes of the northern hemisphere and in the southern countries.

Leatherback turtle (Dermochelys coriacea)

it is the largest tortoise in the world. The span of its front flipper-like limbs reaches 2.5 meters, the mass of reptiles is more than 900 kg, and the dimensions of the shell exceed 2.6 m. The surface of the upper shell is covered not with keratinized plates, but with dense skin, for which the species got its name. The turtle lives in the tropical regions of the Atlantic, Pacific and Indian oceans.

Green turtle (soup turtle) (Chelonia mydas)

The weight of the turtle ranges from 70 to 450 kg, and the size of the shell is from 80 to 150 cm. The color of the skin and carapace can be either olive with a green tint or dark brown with various spots and stripes of white or yellow. The tortoise shell has a small height and oval shape, and its surface is covered with large horny shields. Due to the large size of the head, these reptiles do not hide it inside. The green turtle lives in tropical and subtropical waters of the Atlantic and Pacific oceans.