First description of the vice belongs to Farre (1814). The frequency of this heart defect according to clinical data is 1-3%, according to pathological data - about 1.5% of all congenital heart defects.
With this anomaly, both atria communicate through a common valve or two separate atrioventricular valves with a common ventricle, from which the aorta and pulmonary artery arise.
There is variety anatomical variants of the defect. The most common 4 variants of a three-chamber heart are:
in option I, the only ventricle is represented by the myocardium of the left ventricle;
with type II defect, the entire myocardium has the structure of the right ventricle;
the third type implies the structure of the myocardium of both the right and left ventricles, but the interventricular septum is absent or its rudiment is present;
the fourth type does not have clear differentiation of the myocardium.
Features of hemodynamics with a three-chambered heart, there is a mixing of arterial and venous blood flows in a single ventricular chamber. The aorta and pulmonary artery, which extend directly from the ventricular cavity, have the same systemic pressure, and from birth such a child has hypertension in the pulmonary circulation. Low pulmonary vascular resistance in newborns leads to significant pulmonary vascular hypervolemia. In a single ventricle, a larger volume of oxygenated blood mixes with a smaller volume of venous blood. Initially, arterial hypoxemia in such children is absent or minimal.
Clinical picture variable and depends on concomitant developmental defects and the volume of pulmonary blood flow. A three-chambered heart is most often diagnosed soon after the birth of a child. In a typical case, after birth, shortness of breath, congestive wheezing in the lungs, tachycardia, enlarged liver, repeated pneumonia, and a delay in weight gain appear. In approximately 2/3 of babies, cyanosis appears immediately after birth, which is mildly expressed, has a bluish tint, localized on the lips, fingertips, and intensifies with crying and physical activity. The systolic murmur is soft or not audible, the second heart sound is increased and split.
When combining a common ventricle With pulmonary stenosis, cyanosis appears early. The newborn suffers from shortness of breath and gets tired quickly. Cardiomegaly ranges from mild to moderate. A loud systolic ejection murmur is heard.
Diagnosis of a three-chambered heart.
ECG often reveals difficult-to-differentiate complexes, however, among them one can note unchanged, pointed or double-humped P waves. In some cases, there are signs of enlargement of the right or both ventricles.
Polymorphism electrocardiographic changes are associated with a large number of anatomical and hemodynamic features of this defect. Common to most variants of the defect is a high voltage of the QRS complexes in standard and chest leads, a discrepancy between the degree of ventricular hypertrophy and the deviation of the electrical axis of the heart. Type I defect is characterized by hypertrophy of both ventricles. With type III defect, hypertrophy of the right ventricle predominates. Various types of rhythm disturbances and atrioventricular blockade are also characteristic.
On the radiograph cardiomegaly is determined. In all newborns, against the background of increased pulmonary blood flow, there is an increase in the shadow of the heart due to the right ventricle and atrium.
If the defect is not accompanied by pulmonary artery stenosis, then the pulmonary pattern is strengthened, the main branches of the pulmonary artery bulge.
With pulmonary artery stenosis, the pulmonary pattern is depleted, the cardiac shadow is small, and there is a bulge of the ascending aorta along the upper left edge of the cardiac shadow.
2D echocardiography in the projection from the apex makes it possible to identify the common chamber with one or two atrioventricular valves, the graduate cavity, and transposition of the great vessels. The main echocardiographic sign of the defect is the absence of an echo signal from the interventricular septum. When both atrioventricular valves are present, the mitral valve is located posteriorly, and the tricuspid valve is located to the right. If there is only one valve, then it occupies the entire cavity of a single ventricle.
Forecast. The defect quickly ends in the death of the child from progressive heart failure, cardiac arrhythmias, secondary bronchopulmonary infections and progressive hypoxemia. About 75% of infants with this defect die in the first year of life.
Correction. Surgical correction of the defect is possible.
If a frog came to you for advice on whether it should change its three-chambered heart to a four-chambered one or a two-chambered one (by removing the septum between the atria), what would you advise it?
The frog should be advised to preserve its three-chambered heart. A two-chambered heart would be disadvantageous for a frog for the following reasons. With a three-chambered heart, blood carrying oxygen from the lungs enters the left atrium. Venous blood from muscles, internal organs, etc. enters the right atrium (blood from the skin also enters there). With simultaneous contraction of the atria, blood enters the single ventricle of the frog, but mixes little in it, since the ventricle contains a number of partitions and resembles a sponge in its structure. As a result, mixed blood, rather poor in oxygen, appears in the right half of the ventricle, and oxygen-rich blood in the left half. The analogue of the aorta (conus arteriosus) arises from the right side of the ventricle. The cone contains a special so-called spiral valve. Vessels carrying blood to the lungs and skin depart from the initial part of the cone; then the vessels going to the body and limbs depart; Vessels carrying blood to the brain and sensory organs located on the head extend even further. When the ventricle begins to contract, the pressure in it is still low, the spiral valve opens only the opening of the vessel going to the lungs and skin, and blood from the right half of the ventricle, poor in oxygen, begins to flow there. As the ventricle contracts, the pressure in it increases, and the spiral valve opens the opening of the next vessel; blood richer in oxygen flows to the body and internal organs. Finally, when the pressure increases further, the entrances to the carotid arteries, carrying blood to the head, will open. The most oxygen-rich blood will flow there from the left part of the ventricle, which is furthest away from the conus arteriosus. This blood only to a small extent enters other vessels, which were previously filled with previous portions of blood.
Thus, despite the presence of only one ventricle, the frog has a system for the expedient distribution of blood, enriched in oxygen to varying degrees, between the lungs, internal organs and the brain. If you remove the septum between the atria and make the heart two-chambered, then the blood coming from the lungs and venous blood will mix in this common atrium, which will significantly worsen the functioning of the circulatory system. The same mixed blood will enter the lungs as the brain. The efficiency of the lungs will decrease, the frog will receive less oxygen on average, and its activity level should also decrease. The brain will be especially affected, as it will begin to receive blood that is much poorer in oxygen.
Let us now consider the question of a four-chambered heart. It is easy to realize that in animals with a four-chambered heart, all the blood coming from the body must pass through the lungs, from where it returns to the second atrium. If the pulmonary vessels of a mammal or bird are blocked, all blood flow will stop. Frogs spend a significant part of their lives in water, in particular they spend the winter there. While underwater, the frog with a three-chambered heart can reduce the lumen of the pulmonary vessels and thereby reduce the flow of blood through the inactive lungs; in this case, the blood ejected from the ventricle into the pulmonary cutaneous artery enters mainly the skin and returns to the right atrium.
If the frog's heart were four-chambered and its pulmonary circulation was completely isolated, then this would be unprofitable. The frog would have to pump all the blood through the inactive lungs all winter, spending a noticeable amount of energy on this, which cannot be replenished in winter, and therefore, it would be necessary to accumulate additional reserves before wintering. Thus, a three-chambered heart is indeed most suitable for a frog with its amphibious lifestyle and the important role of cutaneous respiration.
Reptiles are the first completely land animals.
- They feed their young with milk (they have mammary glands).
- there is a diaphragm (muscle, the border between the chest and abdominal cavities).
- differentiated (different) teeth – incisors, canines, molars.
- good brain development, complex behavior.
1. Establish a correspondence between the characteristic of animals and the class for which this characteristic is characteristic: 1) Fish, 2) Amphibians. Write numbers 1 and 2 in the correct order.
A) the presence of a cervical vertebra
B) absence of ribs
B) indirect development
D) the presence of lever limbs
D) two-chamber heart
E) absence of lungs
2. Establish a correspondence between the sign of the circulatory system and the class of vertebrates for which it is characteristic: 1) bony fish, 2) amphibians
A) the heart is filled with venous blood
B) the presence of a three-chambered heart
B) blood mixes in the ventricle of the heart
D) one circle of blood circulation
D) the presence of one atrium
3. Establish a correspondence between the structural features and the classes of animals for which they are characteristic: 1) Bony fish, 2) Amphibians. Write numbers 1 and 2 in the order corresponding to the letters.
A) three-chambered heart
B) division of the spine into caudal and trunk sections
B) one circle of blood circulation
D) paired lungs
D) the presence of a cervical vertebra
E) bare skin covered with mucus
Choose one, the most correct option. Aromorphosis, thanks to which ancient reptiles mastered the terrestrial habitat,
1) internal fertilization
2) protective coloring
3) five-fingered limb
4) three-chambered heart
Establish a correspondence between the type of animal and the structural feature of its heart: 1) three-chamber without a septum in the ventricle, 2) three-chamber with an incomplete septum in the ventricle, 3) four-chamber
A) fast lizard
B) common newt
B) lake frog
Choose three options. Mammals differ from reptiles by having the following characteristics:
1) hair
2) three-chambered heart
3) sweat glands
4) development of the placenta
6) unstable body temperature
Choose one, the most correct option. Reptiles are called true terrestrial animals because they
1) breathe atmospheric oxygen
2) reproduce on land
3) lay eggs
1. Match the characteristics of animals with the classes for which this characteristic is characteristic: 1) amphibians, 2) reptiles
A) internal fertilization
B) fertilization in most species is external
B) indirect development
D) reproduction and development occurs on land
D) thin skin covered with mucus
E) eggs with a large supply of nutrients
2. Establish a correspondence between the animal’s characteristic and the class for which it is characteristic: 1) amphibians, 2) reptiles
A) pulmonary and cutaneous breathing
B) external fertilization
B) dry skin, without glands
D) postembryonic development with transformation
D) reproduction and development occurs on land
E) fertilized eggs with a high yolk content
3. Establish a correspondence between the characteristic and the class for which this characteristic is characteristic: 1) Amphibians, 2) Reptiles. Write numbers 1 and 2 in the order corresponding to the letters.
A) a small supply of nutrients in the eggs
B) cutaneous and pulmonary respiration
B) reproduction and development in water
D) direct postembryonic development
D) dry skin, without glands
E) internal fertilization
4. Establish a correspondence between the sign of an animal and the class to which it belongs: 1) Amphibians 2) Reptiles. Write numbers 1 and 2 in the correct order.
A) thin, mucous skin
B) breathes using the lungs and moist skin
C) the skin is dry, the respiratory organs are lungs
D) three-chambered heart with an incomplete septum in the ventricle
D) three-chambered heart without a septum in the ventricle
E) reproduces in water
5. Establish a correspondence between the characteristics and the classes of animals to which they belong: 1) Reptiles, 2) Amphibians. Write numbers 1 and 2 in the order corresponding to the letters.
A) the skin contains many glands
B) the body is covered with horny scales
B) there is a trachea and a bronchial system
D) the cervical spine is represented by one vertebra
D) the chest is absent
E) there is an incomplete septum in the ventricle of the heart
Choose one, the most correct option. A three-chambered heart with an incomplete septum in the ventricle was formed in the process of evolution in
Choose one, the most correct option. In the process of evolution, two atria in the heart first appeared in
Establish a correspondence between the trait and the class of chordates for which this trait is characteristic: 1) Mammals 2) Birds
A) lack of teeth
B) participation of the skin in thermoregulation
B) participation in the respiration of air sacs
D) alveolar structure of the lungs
D) filling bone cavities with air
E) the presence of convolutions and grooves in the cerebral cortex
Choose one, the most correct option. Mammals are different from other vertebrates
1) constant body temperature
2) sexual reproduction
3) the presence of hair
4) the presence of five parts of the brain
Choose three options. In birds, as in reptiles
1) dry skin, devoid of glands
2) missing teeth
3) the integument consists of horny substance
4) four-chambered heart
5) arterial blood does not mix with venous blood
6) intestines, ureters, reproductive organs open into the cloaca
1. Establish a correspondence between the sign of an animal and the class for which it is characteristic: 1) Birds, 2) Reptiles
B) body temperature depends on the ambient temperature
C) three-chambered heart, two circles of blood circulation
D) the body usually comes into contact with the ground when moving
D) double breathing is characteristic
E) arterial and venous blood do not mix in the heart
2. Establish a correspondence between the trait and the class of vertebrate animals for which it is characteristic: 1) Reptiles, 2) Birds. Write numbers 1 and 2 in the correct order.
A) unstable body temperature
B) intensive metabolism in cells
B) absence of a bladder
D) four-chambered heart
D) incomplete septum in the ventricle of the heart
3. Establish a correspondence between the characteristic of a vertebrate animal and the class for which it is characteristic: 1) Reptiles, 2) Birds. Write numbers 1 and 2 in the correct order.
A) three-chambered heart with an incomplete septum in the ventricle
B) arterial and venous blood do not mix in the heart
B) have a constant body temperature
D) the presence of hollow bones filled with air
D) the presence of a tarsus
E) the presence of horny scales on the body
4. Establish a correspondence between the features and the classes of animals for which they are characteristic: 1) Birds, 2) Reptiles. Write numbers 1 and 2 in the order corresponding to the letters.
A) the presence of a tarsus on the hind limb
B) lack of care for offspring in most species
B) absence of a bladder
D) presence of teeth
D) the presence of the coccygeal gland
It is known that the class Mammals has characteristic features. Select three statements from the text below that relate to the characteristics of this class. (1) Internal organs in mammals are located in body cavities, which are separated from each other by the diaphragm into two: thoracic and abdominal. (2) The chest cavity contains the lungs, heart, and the abdominal cavity contains the stomach, intestines and other organs. (3) The lungs of mammals are called corpus spongiosum. (4) In the oral cavity, differentiated teeth mechanically crush food, and then it is chemically processed by enzymes of digestive juices. (5) The process of filtering blood from metabolic end products is carried out by the trunk kidneys. (6) Mammalian skin is dry without glands.
1. Choose three correct answers out of six and write down the numbers under which they are indicated. If, in the process of evolution, an animal has formed the brain shown in the figure, then this animal is characterized by
1) four-chambered heart
2) external fertilization
5) cellular lungs
6) development of the embryo in the uterus
2. Choose three correct answers out of six and write down the numbers under which they are indicated. If, in the process of evolution, an animal has formed the brain shown in the figure, then this animal is characterized by
1) three-chambered heart
2) internal fertilization
3) the skin is thin, dry, practically devoid of glands
4) constant body temperature
5) cellular lungs
Choose three correct answers out of six and write down the numbers under which they are indicated. What characteristics are common to humans and mammals?
2) indirect development
3) open circulatory system
4) three-chambered heart
5) presence of a diaphragm
6) the presence of skin derivatives - sebaceous glands
Establish a correspondence between the characteristics of animal skin and the class for which it is characteristic: 1) Reptiles, 2) Amphibians. Write numbers 1 and 2 in the correct order.
A) forms bone plates
B) contains an abundance of glands
B) forms horny outgrowths
D) absorbs water
D) abundantly supplied with capillaries, thin
E) provides gas exchange
1. Establish a correspondence between vertebrate animals with the characteristics of their body temperature: 1) constant, 2) variable. Write numbers 1 and 2 in the correct order.
A) house sparrow
B) quick lizard
B) common dolphin
D) Nile crocodile
D) common newt
E) common mole
2. Establish a correspondence between animals and the characteristics of their body temperature: 1) constant, 2) variable. Write numbers 1 and 2 in the order corresponding to the letters.
A) waterfowl
B) lobe-finned fish
D) tailless amphibians
D) scaly reptiles
E) great apes
3. Establish a correspondence between animals and physiological characteristics: 1) warm-blooded, 2) cold-blooded. Write the numbers 1 and 2 in the sequence corresponding to the letters.
4. Establish a correspondence between organisms and their metabolic levels: 1) warm-blooded, 2) cold-blooded. Write numbers 1 and 2 in the order corresponding to the letters.
A) grass frog
B) barn swallow
D) common fox
D) quick lizard
E) common pike
Establish a correspondence between the features of the respiratory system and the classes for which these features are characteristic: 1) Amphibians, 2) Birds. Write numbers 1 and 2 in the correct order.
A) there are air bags
B) the lungs have a spongy structure
C) ratio of skin surface to lung surface 2:3
D) the lungs are represented by hollow sacs
D) double breathing
E) partially cutaneous breathing
Establish a correspondence between the type of animal and the structure of its heart: 1) three-chamber, 2) two-chamber. Write numbers 1 and 2 in the correct order.
B) blue shark
B) pond frog
D) common newt
D) common pike
Analyze the text “Characteristics of the Amphibians class.” For each cell indicated by a letter, select the corresponding term from the list provided. Amphibians go through the _______(A) stage in their development. This brings them closer to fish. Respiration in amphibians _______(B). They have a heart _______(B), and in connection with reaching land, _______(D) and lungs appeared.
2) Pulmonary breathing
3) Pulmonary-cutaneous respiration
4) Two-chamber heart
5) Three-chambered heart
6) Swim bladder
7) Second circle of blood circulation
Choose three correct answers out of six and write down the numbers under which they are indicated. If, in the process of evolution, an animal developed the lungs shown in the figure, then this animal is characterized by
1) four-chambered heart
2) external fertilization
3) skin with scales or scutes
4) constant body temperature
5) laying eggs with a thick shell
6) development of the embryo in the uterus
Choose one, the most correct option. Which of the following features indicates the complexity of the organization of mammals compared to reptiles?
1) increase in the gas exchange surface in the lungs
2) the appearance of the internal skeleton
3) increase in the number of body parts
4) changes in the structure of the limbs
Choose three correct answers out of six and write down the numbers under which they are indicated. Animals with the lungs shown in the figure are characterized by the following characteristics:
1) feather cover of the body
2) high metabolic rate
3) three-chambered heart with an incomplete septum in the ventricle
4) the skin contains many glands
5) presence of a diaphragm
6) reproduce sexually, lay shelled eggs
Establish a correspondence between the animal and the number of chambers of its heart: 1) two, 2) three. Write numbers 1 and 2 in the order corresponding to the letters.
Rank the animals according to the complexity of their heart structure during evolution. Write down the corresponding sequence of numbers.
From the text below, select three features related to the adaptation of birds to flight. Write down the numbers corresponding to the selected answers. (1) The compact body of birds has an egg-shaped, streamlined shape. (2) Like mammals, birds are warm-blooded animals. (3) The cloaca of birds is a cavity into which the digestive tract, ureters and excretory ducts of the reproductive system open. (4) Some bones have air-filled cavities. (5) The coccygeal gland, located above the root of the tail, secretes an oily secretion that serves for lubrication. (6) Birds have air sacs that enable double breathing.
Choose three correct answers out of six and write down the numbers under which they are indicated. If, in the process of evolution, an animal has formed the brain shown in the figure, then this animal is characterized by
1) double breathing
2) the presence of mammary glands
3) numerous skin glands
4) four-chambered heart
5) compound eyes
Choose three correct answers out of six and write down the numbers under which they are indicated. Representatives of cold-blooded animals are
Choose three correct answers out of six and write down the numbers under which they are indicated. What animals belong to the class of reptiles?
1) common viper
2) pond frog
3) common newt
4) Nile crocodile
6) viviparous lizard
Choose three correct answers out of six and write down the numbers under which they are indicated in the table. Reptiles are characterized by
1) reproduction on land
2) constant body temperature
3) direct development
4) articulated body
5) internal fertilization
6) supply the cells of the internal organs of the body with arterial blood
Choose one, the most correct option. The complexity of the structure of the respiratory system of mammals, compared to reptiles, consists in
1) the appearance of the right and left lungs
2) presence of trachea and bronchi
3) increasing the respiratory surface of the lungs
4) the presence of nostrils and nasal cavity
Establish a correspondence between the characteristics of reproduction and the classes of animals for which they are characteristic: 1) Amphibians, 2) Mammals. Write numbers 1 and 2 in the order corresponding to the letters.
A) an egg with a large supply of nutrients
B) development of the embryo in the uterus
B) the presence of a placenta
D) development with metamorphosis
D) the presence of a larval stage in development
E) fertilization in the oviducts
Establish a correspondence between the characteristics and classes of animals for which these characteristics are characteristic: 1) Reptiles, 2) Mammals. Write numbers 1 and 2 in the order corresponding to the letters.
A) complete separation of arterial and venous blood
B) embryonic development in the egg in all species
B) the presence of sweat glands
D) differentiated alveolar teeth
D) three-chambered heart with an incomplete septum in the ventricle
E) the presence of grooves and convolutions in the cerebral cortex
Find three errors in the given text. Indicate the numbers of sentences in which errors were made. (1) Amphibians are vertebrate animals that live in water and on land. (2) They swim well; swimming membranes are developed between the toes of the hind legs of tailless amphibians. (3) Amphibians move on land using two pairs of five-fingered limbs. (4) Amphibians breathe using their lungs and skin. (5) Adult amphibians have a two-chambered heart. (6) Fertilization in tailless amphibians is internal; tadpoles develop from fertilized eggs. (7) Amphibians include the lake frog, gray toad, water snake, and crested newt.
Establish a correspondence between animals and the habitats in which they breed: 1) aquatic, 2) ground-air. Write numbers 1 and 2 in the order corresponding to the letters.
Tasks No. 13 with explanations
1. The complexity of the circulatory system compared to reptiles is evidenced by
1. The presence of two atria in the heart
2. Formation of an incomplete septum in the ventricle of the heart
3. The appearance of a three-chambered heart
4. Complete separation of venous and arterial blood
Explanation: reptiles have a three-chambered heart with an incomplete septum in the ventricle, due to which the blood mixes, two circles of blood circulation. Mammals have two ventricles (accordingly, a complete septum between them), two circles of blood circulation, and the blood does not mix. The correct answer is 4.
2. Complex forms of behavior due to the presence of the cerebral cortex appear in
Explanation: Complex behaviors associated with a developed cerebral cortex are characteristic of mammals. The correct answer is 4.
3. Which part of the hearing organ of vertebrates develops only in mammals?
1. Middle ear cavity
2. Inner ear
3. Eustachian tube
4. Auricle
Explanation: no class of animals, except mammals, has an auricle, but all other parts of the auditory analyzer do. The correct answer is 4.
4. An ordinary dolphin, plunging into the depths of the sea, consumes the oxygen contained in
2. Body cavities
3. Air bags
Explanation: the dolphin is a secondary aquatic mammal, that is, the dolphin's ancestors lived on land. And, like any other mammal, it has lungs in its respiratory system with which it breathes. It has neither air sacs (like birds), nor gills (like fish), and air does not accumulate in the body cavities either. The correct answer is 1.
5. In the process of evolution, which vertebrates first developed a three-chambered heart and lungs?
Explanation: a three-chambered heart and lungs appeared in animals whose development is not associated with water, these are reptiles. The correct answer is 1.
6. In mammals, gas exchange occurs in
4. Pulmonary vesicles
Explanation: mammals are the most highly organized animals and their gas exchange occurs in the pulmonary vesicles (alveoli). The correct answer is 4.
3. Three-chamber, with a septum in the stomach
4. Three-chamber, without a partition in the stomach
Explanation: birds are fairly highly organized animals with an intense metabolism and warm-bloodedness, so their heart consists of four chambers: two atria and two ventricles. The correct answer is 1.
8. Internal fertilization is typical for
2. Tailless amphibians
3. Tailed amphibians
Explanation: internal fertilization is characteristic of organisms that do not require water for development. Such organisms are, of the listed, reptiles. The correct answer is 4.
9. An incomplete septum in the ventricle of the heart appeared in the process of evolution in
Explanation: birds have a four-chambered heart, that is, the septum between the ventricles is complete (as in mammals), in amphibians there is no septum at all, so the heart is three-chambered, and in reptiles an incomplete septum appears, but already in crocodiles it becomes complete and they have a four-chambered heart. The correct answer is 4.
10. Air sacs as part of the respiratory system are present in
Explanation: Air sacs are an adaptation to flight, so they are part of the respiratory system of birds. The correct answer is 1.
11. Characteristics that distinguish amphibians from other vertebrates include
1. Dismembered limbs and differentiated spine
2. Heart with an incomplete septum in the ventricle
3. Bare mucous skin and external fertilization
4. Closed circulatory system and two-chamber heart
Explanation: All vertebrates have segmented limbs and differentiated spines, reptiles have a heart with an incomplete septum in the ventricle, fish have a closed circulatory system and a two-chambered heart, and amphibians have bare skin and external fertilization. The correct answer is 3.
12. A high metabolic rate allows birds
1. Take care of the offspring
2. Lay eggs in nests
3. Eat a plant-based diet
4. Expend a lot of energy during the flight
Explanation: a high metabolic rate is one of the adaptations for flight, so we choose to expend a large amount of energy during flight. The correct answer is 4.
13. One of the signs of the complication of birds and mammals compared to reptiles is
1. Division of the body into sections
2. Constant body temperature
3. Internal skeleton
4. Presence of organ systems
Explanation: Birds and mammals, unlike all other animals, have a three-chambered heart and a constant body temperature. The correct answer is 2.
14. The highest level of metabolism is characteristic of
Explanation: the highest level of metabolism is characteristic of the most highly organized group of animals. Among the answer options presented, the most progressive group is mammals. The correct answer is 4.
15. Mammary glands of mammals are modified glands
Explanation: mammary glands are exocrine glands that arose from sweat glands (that is, they are modified sweat glands). The correct answer is 1.
16. Which of the listed characters first appeared in chordates?
2. Nervous system
3. Circulatory system
4. Internal skeleton
Explanation: the vast majority of chordates have an internal bony skeleton (or cartilaginous), this is a progressive feature. The correct answer is 4.
Tasks for independent solution
1. Which of the following animals first developed a spine during the process of evolution?
The correct answer is 4.
2. Lancelet belongs to the group of animals
The correct answer is 3.
3. Vertebrates with a three-chambered heart, closely related to the aquatic environment, are combined into a class
The correct answer is 3.
4. What kind of blood are supplied to the body cells of vertebrates?
4. Saturated with carbon dioxide
The correct answer is 3.
5. Arterial blood in the heart does not mix with venous blood
1. Most reptiles
2. Birds and mammals
3. Tailed amphibians
4. Tailless amphibians
The correct answer is 2.
6. What animals have an external skeleton made of chitin?
1. Bivalves
4. Gastropods
The correct answer is 3.
7. Which part of the brain is most developed in mammals?
1. Forebrain
4. Diencephalon
The correct answer is 1.
8. In which of the listed groups of animals, in the process of evolution, two atria first appeared in the heart?
The correct answer is 3.
9. Vertebrates with a three-chambered heart, pulmonary and cutaneous respiration, -
2. Cartilaginous fish
The correct answer is 1.
10. The systemic and pulmonary circulation have
4. Cartilaginous fish
The correct answer is 1.
11. Snakes are different from lizards
1. The presence of horny cover
2. Feeding on live prey
3. Fused transparent eyelids
4. The ability to hide in holes
The correct answer is 3.
12. Dry skin with horny scales or scutes covers the body
The correct answer is 2.
13. Among vertebrates, the circulatory and nervous systems have the most complex structure
1. Cartilaginous and bony fish
2. Tailed and tailless amphibians
3. Aquatic reptiles
4. Birds and mammals
The correct answer is 4.
14. How do higher mammals differ from marsupials?
1. Development of the coat
2. Duration of intrauterine development
3. Feeding offspring with milk
4. Internal fertilization
The correct answer is 2.
15. Bats navigate in flight using
2. Organs of vision
3. Taste organs
4. Ultraviolet rays
The correct answer is 1.
16. Snakes can swallow prey many times the diameter of their body thanks to
1. Flattened head and wide mouth
2. A small number of teeth and a voluminous stomach
3. High mobility of the jaw bones
4. Large head and body sizes
The correct answer is 3.
17. Birds differ from reptiles in character
1. The presence of yolk in the egg
2. Reproduction by eggs
3. Feeding offspring
4. Reproduction on land
The correct answer is 3.
18. Vertebrates that have a three-chambered heart and bare skin are classified as
The correct answer is 4.
19. Mammals can be distinguished from other vertebrates by the presence
1. Hair and ears
2. Dry skin with horny scales
3. Claws and tail
4. Four limb running type
The correct answer is 1.
20. The tadpole’s heart resembles a heart in structure
4. Adult amphibian
The correct answer is 1.
21. Skullless animals have a skeleton
3. Consists of chitin
4. Represented by a chord
The correct answer is 4.
22. The body cavity, mantle and shell have
The correct answer is 3.
23. In the distribution of mammals among orders, the most important feature is
1. The nature of the body cover
2. Teeth structure
3. Habitat
The correct answer is 2.
24. Bony fish, unlike cartilaginous fish,
1. They have paired fins
2. Covered with scales
3. Have a swim bladder
4. They live in the depths of the ocean
The correct answer is 3.
25. Body cells are supplied with more oxygen in animals with
1. Gill breathing
2. Unclosed circulatory system
3. Indirect development
4. Constant body temperature
The correct answer is 4.
26. Fish determine the direction and speed of water movement, the distance to underwater objects, and the depth of immersion with the help of an organ
4. Lateral line
The correct answer is 4.
27. The body shape of tadpoles, the presence of a lateral line, gills, a two-chambered heart, and one circulation indicate that amphibians are related to
The correct answer is 4.
28. Mammals differ from other vertebrates in the presence
1. Nervous system
2. Five parts of the brain
3. Hairline
4. Sexual reproduction
The correct answer is 3.
The correct answer is 4.
30. You can recognize amphibians among vertebrates of other classes by
1. Having two pairs of limbs
2. Skin with bone scales covered with mucus
3. Dry skin with horny scales or scutes
4. Bare, moist skin with many glands
The correct answer is 4.
31. Complex forms of behavior due to the presence of the cerebral cortex appear in
The correct answer is 4.
32. An ordinary dolphin, plunging into the depths of the sea, consumes the oxygen contained in
2. Body cavities
3. Air bags
The correct answer is 1.
33. In the process of evolution, which vertebrates first developed a three-chambered heart and lungs?
They have a three-chambered heart, with an incomplete septum in the ventricle
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Reptiles
“The most ancient reptiles” - Has a long tail with a diamond-shaped extension at the end. Seymouria occupies an intermediate position between amphibians and ancient reptiles. The legs are weak and short with claws that are used to hold onto trees and rocks. Groups of dinosaurs. Brontosaurus and Diplodocus had long necks to reach succulent foliage on tall trees, while Iguanodon and Anatosaurus stood on strong hind limbs when feeding.
“Yellowbellied” - Presentation on the topic: Yellowbellied (Pseudopus apodus). ? Ananyeva N. B., Bor L. Ya., Darevsky I. S., Orlov N. L. Five-language dictionary of animal names. External description. Relatives of the yellowbell are slender armored spindles from the genus Ophisaurus. Reaction to a person. Historical fact. In captivity, it quickly gets used to taking food from hands.
“Class reptiles” - Lizards’ skin sheds in pieces. Scaly eyes. General characteristics of the class Reptiles. What is the role of amphibians in nature. In the water - ichthyosaurs and plesiosaurs. Zoo quiz. . The digestive system includes the stomach and cecum. External structure of a LIZARD. - Why is the skin of a frog covered not with water, but with mucus?
"Reptiles" - Reptiles. Sea leatherback turtle Giant turtle (length up to 2 m and weight up to 600 kg). Anaconda From the boa constrictor family, reaches in length. Reptiles The similarity of reptiles to other animals Distinctive features of reptiles The most ancient reptiles Reptiles are giants.
“Internal structure of reptiles” - Venous blood. What is special about the lizard's respiratory system? Determine which diagram of the structure of the heart belongs to fish, frog, lizard. Digestion of proteins. What are the features of the internal structure of the chameleon lizard? Right atrium. There is a tensile ligament in front of the jaw. What are the similarities and differences between the skeleton of a frog and the skeleton of a lizard?
“Orders of reptiles” - Order Scaly Lizards. Hence the name - “reptiles” - covered with scales. Reptile class. Most of them live on land. Squad Crocodiles. Habitats. Skeleton of reptiles. Order Beakheads. Reptiles are terrestrial animals. External structure of reptiles. Origin of Reptiles.
There are a total of 17 presentations in the topic “Reptiles”
All about ventricular septal defect in newborns, children and adults
From this article you will learn about the heart defect in the form of a ventricular septal defect. What kind of developmental disorder is this, when does it occur and how does it manifest itself? Features of diagnosis and treatment of the disease. How long do they live with such a defect?
A ventricular septal defect (VSD) is a disruption of the integrity of the wall between the left and right ventricles of the heart that occurs during the development of the embryo at 4–17 weeks of pregnancy.
This pathology in 20% of cases is combined with other malformations of the heart muscle (Fallot, complete opening of the atrioventricular canal, transposition of the main cardiac vessels).
With a septal defect, a connection is formed between two of the four chambers of the heart muscle and blood is “dumped” from the left to the right (left-to-right shunt) due to higher pressure in this half of the heart.
Symptoms of a significant isolated defect begin to manifest themselves at 6–8 weeks of a child’s life, when increased pressure in the pulmonary vascular system (physiologically for this period of life) normalizes and reflux of arterial blood into venous blood occurs.
This blood flow anomaly gradually leads to the following pathological processes:
- expansion of the cavities of the left atrium and ventricle with significant thickening of the wall of the latter;
- increased pressure in the blood flow system of the lungs with the development of hypertension in them;
- progressive increase in heart failure.
A window between the ventricles is a pathology that does not occur during a person’s life; such a defect can only develop during pregnancy, therefore it is classified as congenital heart defects.
In adults (people over 18 years of age), this defect can persist throughout life, provided that the communication between the ventricles is small and (or) the treatment is effective. There is no difference in the clinical manifestations of the disease between children and adults, with the exception of stages of normal development.
The danger of the defect depends on the size of the defect in the septum:
- small and medium-sized ones are almost never accompanied by disruption of the heart and lungs;
- large ones can cause the death of a child from 0 to 18 years of age, but more often fatal complications develop in infancy (children of the first year of life) if treatment is not carried out in time.
This pathology is easily correctable: some defects close spontaneously, others occur without clinical manifestations of the disease. Large defects are successfully eliminated surgically after the preparatory stage of drug therapy.
Serious complications that can cause death usually develop with combined forms of cardiac dysfunction (described above).
Diagnosis, observation and treatment of patients with VSD are carried out by pediatricians, pediatric cardiologists and vascular surgeons.
How common is the vice?
Disturbances in the structure of the wall between the ventricles rank second in frequency among all heart defects. The defect is registered in 2–6 children per 1000 live births. Among infants born before term (premature) – in 4.5–7%.
If the technical equipment of a children's clinic allows ultrasound examination of all infants, then a violation of the integrity of the septum is recorded in 50 newborns out of every 1000. Most of these defects are small in size, so they are not detected by other diagnostic methods and do not affect the development of the child in any way.
A defect of the interventricular septum is the most common manifestation of a violation of the number of genes in a child (chromosomal diseases): Down syndrome, Edwards syndrome, Patau syndrome, etc. But in more than 95% of cases, the defect is not combined with disturbances in the structure of chromosomes.
A defect in the integrity of the wall between the ventricles of the heart is detected in 56% of cases in girls and in 44% in boys.
Why does it occur
Violation of the formation of the septum can occur for several reasons.
Diabetes mellitus with poorly adjusted sugar levels
Phenylketonuria is a hereditary pathology of amino acid metabolism in the body.
Infections – rubella, chickenpox, syphilis, etc.
In case of twins birth
Teratogens are drugs that cause disruption of fetal development.
Classification
Depending on the location of the window, several types of defect are distinguished:
Symptoms
A ventricular septal defect in a newborn (a child in the first 28 days of life) manifests itself only in the case of a large window or in combination with other defects; if this is not the case, clinical symptoms of a significant defect appear only after 6–8 weeks. The severity depends on the volume of blood discharge from the left chambers of the heart to the right.
Small defect
- There are no clinical manifestations.
- Child nutrition, weight gain and development without deviations from the norm.
Moderate defect
Clinical manifestations in premature infants occur much earlier. Any infection of the respiratory system (nose, throat, trachea, lungs) accelerates the onset of symptoms of a cardiac problem due to an increase in venous blood pressure in the lungs and a decrease in their compliance:
- moderate increase in breathing (tachypnea) - more than 40 per minute in infants;
- participation in breathing of auxiliary muscles (shoulder girdle);
- sweating;
- weakness when feeding, forcing you to take rest breaks;
- low monthly weight gain against the background of normal growth.
Large defect
The same symptoms as with a moderate defect, but in a more pronounced form, in addition:
- blue discoloration of the face and neck (central cyanosis) due to physical activity;
- Constant bluish discoloration of the skin is a sign of a combined defect.
As the pressure in the pulmonary blood flow system increases, manifestations of hypertension in the pulmonary circulation join:
- Difficulty breathing with any exertion.
- Chest pain.
- Pre-fainting and fainting states.
- Squatting relieves the condition.
Diagnostics
It is impossible to identify a ventricular septal defect in children based only on clinical manifestations, given that the complaints are not specific.
Physical data: external examination, palpation and auscultation
Increased apical impulse
Second tone splitting
Rough systolic murmur to the left of the sternum
Rough systolic murmur in the lower third of the sternum on the left
There is a noticeable trembling of the chest during myocardial contraction
Moderate increase in second tone
Short systolic murmur or its complete absence
Pronounced accent of the second tone, noticeable even on palpation
A pathological third tone is heard
There is often wheezing in the lungs and an enlarged liver
Electrocardiography (ECG)
With progression of heart failure – thickening of the right ventricle
Thickening of the right atrium
Deviation of the electrical axis of the heart to the left
With severe pulmonary hypertension, there is no thickening of the left chambers of the heart
Chest X-ray
Increased pulmonary pattern in the central sections
Dilatation of the pulmonary artery and left atrium
Right ventricular enlargement
When combined with pulmonary hypertension, the vascular pattern is weakened
Echocardiography (EchoCG) or ultrasonography (ultrasound) of the heart
Allows you to identify the presence, location and size of VSD. The study provides clear signs of myocardial dysfunction based on:
- the approximate level of pressure in the chambers of the heart muscle and pulmonary artery;
- pressure differences between the ventricles;
- sizes of the cavities of the ventricles and atria;
- the thickness of their walls;
- the volume of blood that the heart pumps out when it contracts.
The size of the defect is assessed in relation to the base of the aorta:
Cardiac catheterization
Used only in complex diagnostic cases, it allows you to determine:
- type of malformation;
- window size between the ventricles;
- accurately assess the pressure in all cavities of the heart muscle and central vessels;
- degree of blood discharge;
- expansion of the heart chambers and their functional level.
Computed and magnetic tomography
- These are highly sensitive research methods with great diagnostic value.
- They completely eliminate the need for invasive diagnostic methods.
- Based on the results, it is possible to construct a three-dimensional reconstruction of the heart and blood vessels to select the optimal surgical tactics.
- The high price and specificity of the study do not allow them to be carried out on a regular basis - diagnostics of this level are carried out only in specialized vascular centers.
Complications of the defect
- Pulmonary hypertension (Eisenmenger syndrome) is the most severe complication. Changes in the blood vessels of the lungs cannot be cured. They lead to the reverse flow of blood from the right to the left, which quickly manifests itself as symptoms of heart failure and leads to the death of patients.
- Secondary aortic valve insufficiency usually occurs in children over two years of age and occurs in 5% of cases.
- Significant narrowing of the right ventricular outflow tract occurs in 7% of patients.
- Infectious and inflammatory changes in the internal lining of the heart (endocarditis) - rarely occurs before the child is two years old. The changes involve both ventricles, most often located in the area of the defect or on the leaflets of the tricuspid valve.
- Blockage (embolism) of large arteries by bacterial blood clots against the background of an inflammatory process is a very common complication of endocarditis due to a defect in the wall between the ventricles.
Treatment
Small VSD does not require treatment. Children develop in accordance with norms and live full lives.
Antibacterial prevention of pathogens entering the bloodstream that can cause endocarditis is indicated during dental treatment or infectious diseases of the oral cavity and respiratory system.
This defect does not affect the quality of life, even if it does not close on its own. Adult patients should be aware of their pathology and warn medical personnel about the disease during any treatment for other diseases.
Children with moderate and major defects are monitored by cardiologists throughout their lives. They are given treatment that compensates for the manifestations of the disease or, in the case of surgery, can relieve the pathology. There are moderate restrictions on mobility and the risk of inflammation of the inner lining of the heart, but life expectancy is the same as in people without a defect.
Drug treatment
Indications: moderate to large defect in the septum between the ventricles.
- diuretics to reduce the load on the heart muscle (Furosemide, Spironolactone);
- ACE inhibitors, which help the myocardium under conditions of increased stress, dilate blood vessels in the lungs and kidneys, and reduce blood pressure (Captopril);
- cardiac glycosides that improve myocardial contractility and conduction of excitation along nerve fibers (Digoxin).
Drugs for ventricular septal defect
Surgery
- Lack of effect from drug correction in the form of progression of heart failure with impaired child development.
- Frequent infectious and inflammatory processes of the respiratory tract, especially the bronchi and lungs.
- Large septal defects with increased pressure in the blood flow system of the lungs, even without a decrease in heart function.
- The presence of bacterial deposits (vegetations) on the internal elements of the heart chambers.
- The first signs of disruption of the aortic valve (incomplete closure of the valves according to ultrasound examination).
- The size of the muscle defect is more than 2 cm when it is located in the area of the apex of the heart.
- Endovascular operations (minimally invasive, not requiring extensive surgical access) – fixation of a special patch or occluder in the area of the defect.
It is impossible to use with large windows between the ventricles, since there is no room for fixation. Used for muscular type of defect.
If the defect size is moderate, two flaps are connected from the side of each ventricle, fixing them to the septal tissue.
A large defect is covered with one large patch made of medical material.
The risk of death during surgical treatment in the first two months of life is 10–20%, and after 6 months – 1–2%. Therefore, any necessary surgical correction of heart defects is attempted in the second half of the first year of life.
After surgery, especially endovascular surgery, the defect may reopen. With repeated operations, the risk of fatal complications increases to 5%.
Forecast
Isolated VSDs are easily correctable, subject to timely diagnosis, observation and the necessary treatment.
- With the muscular version of the defect, if the defect is small or moderate in size, 80% of the pathological messages close spontaneously during the first two years, another 10% can close at a later age. Large septal defects do not close, but are reduced in size, allowing surgery to be performed with less risk of complications.
- Perimembranous defects close spontaneously in 35–40% of patients, while in some of them a septal aneurysm forms in the area of the former window.
- The infundibular type of violation of the integrity of the septum between the ventricles cannot close on its own. All defects of moderate and large diameter require surgical correction during the second half of the child's first year of life.
- Children with small defects do not require any therapy, but only dynamic observation.
All patients with such a heart defect are prescribed antibacterial prophylaxis during dental procedures, due to the risk of developing inflammation of the inner lining of the heart.
Limitation on the level of physical activity is indicated for any type of defect of moderate and large diameter until its spontaneous healing or surgical closure. After the operation, children are observed by a cardiologist and, in the absence of relapse, are allowed to participate in any type of exercise for one year.
The overall mortality rate in cases of disruption of the structure of the wall between the ventricles, including postoperative mortality, is about 10%.
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In the course of evolution, the blood system became more complex. From the moment the heart appears, the number of its chambers increases, and the vessels extending from it are differentiated. A three-chambered heart provides organisms with a number of advantages over a more simply constructed organ. Animals have higher vital energy.
Complication of the structure of the heart
The anterior part of the abdominal vessel pulsates in the lancelet.
In fish, the heart already consists of one atrium and one ventricle.
Who has a three-chambered heart? In amphibians, the atrium has two parts that open into the ventricle with a common opening.
This is also typical for reptiles. Already in lizards, snakes, turtles and crocodiles, each atrium has an independent opening that opens into the ventricle. The holes have valves. Reptiles, like amphibians, have a single ventricle, but it is divided by an incomplete septum that grows from bottom to top.
Birds and animals that feed their young with milk have two atria and the same number of ventricles. Both the atria and ventricles are completely separate from each other.
From the above list it is clear that a three-chambered heart is characteristic of amphibians and reptiles. However, the structure still differs not only among the classes of these animals, but also between genera. Thus, in crocodiles the septum between the back parts of the heart is almost complete. Despite this fact, crocodiles remain cold-blooded animals, because blood containing a large percentage of carbon dioxide enters the main arterial trunk. Mixed blood flows through the vessels leading to the body.
Outgrowths in the ventricle of the heart as the beginning of the formation of a septum
Those with a three-chambered heart have pulmonary and systemic circulations. This improves the overall standard of living. Moreover, those who have a three-chambered heart have a tendency to form outgrowths in the ventricle. The frog already has numerous protrusions, which significantly separates the arterial blood from that in which there is a high content of carbon dioxide. However, tadpoles have a single blood circulation.
The structure of the three-chambered heart of a frog
Amphibians have a heart with three chambers.
The ventricle has thick walls. The atria communicate with the ventricle through a common opening. The right atrium is larger in volume. It receives blood from all over the body, which has given off an element of oxidation. The left side of the heart receives blood from the lungs. The venous sinus is connected to the right atrium. It pumps blood to the heart. On the right side is the conus arteriosus. It is also present in lower fish. Includes a number of valves. Serves to pump blood into vessels. In amphibians, the cone is divided into two sections by a septum.
Diagram of blood flow in the heart of a frog
Blood with a high content of carbon dioxide mixed with oxygenated blood flows into the right atrium, and only enriched with an element for oxidation into the left atrium. The atria contract simultaneously. The blood passes into a single ventricle. Here the outgrowths prevent strong mixing of the blood. The conus arteriosus extends to the right of the ventricle, so blood containing a larger amount of carbon dioxide flows here first. It fills the cutaneous pulmonary arteries. The cone has a spiral valve. As blood pressure increases, it moves, opening the opening of the aortic arches. Mixed blood rushes here from the middle part of the ventricle. Next, the blood pressure increases even more, and the spiral valve opens the mouths of the carotid arteries, which go to the head. Blood flows into the carotid arteries, since the remaining vessels are already filled.
Circulatory system of lizards and other reptiles
In lizards and snakes, the two circulations are not completely separated. But the degree of their separation is higher than that of amphibians. Two aortic arches are preserved. The ventricle has a wall, but it does not completely separate into two halves. It is believed that crocodiles have a four-chambered heart. Although the hole between the ventricles still remains.
Thus, with a three-chambered heart they have greater mobility compared to fish. They can go to land, where they feel great. Life activity has increased evolutionarily.
Individuals with a three- and four-chambered heart always have two circles of blood circulation, which also greatly increases the mobility of organisms. And for land vertebrates, this is necessary in conditions where holding the body is many times heavier than in an aquatic environment. With two circulations, the oxygen-carrying blood is under sufficient pressure as it passes through the heart again. And it does not mix with the venous one.
Some frogs come out of hiding in early spring, when the snow has not yet melted. Grass frogs are among the first to appear in the middle zone.
Those with a three-chambered heart have greater mobility in cold conditions than other cold-blooded representatives.
The same organs in different species may differ in structure and functionality. Our own heart has four separate chambers, while frogs, toads, snakes and lizards can get by with just three. You can learn about the functionality of three-chambered hearts in this article.
Vertebrate classes and cardiac chambers
Vertebrates are represented by various classes: fish, amphibians, reptiles, mammals and birds. In vertebrates, the heart performs blood pumping function throughout the body this is called blood circulation. Although the circulatory systems are similar in many ways, the hearts of different classes of vertebrates have different numbers of chambers. These chambers determine how efficiently the heart carries oxygen-rich blood and oxygen-poor blood back to the heart.
Vertebrates can be divided by the number of heart chambers:
- Two chambers: one atrium and one ventricle (fish)
- Three chambers: two atria and one ventricle (amphibians, amphibians and reptiles)
- Four chambers: two atria and two ventricles (birds and mammals)
Circulation
The most vital substance, oxygen, enters the blood through the gills or lungs. To achieve more efficient use of oxygen, many vertebrates have two separate stages of blood circulation: pulmonary and systemic.
In chamber pulmonary circulation, the heart sends blood to the lungs to enrich it with oxygen. The process begins in the ventricle, from there, through the pulmonary arteries, it enters the lungs. Blood returns from the lungs through the pulmonary veins and flows into the left atrium. From there it enters the ventricle, where the systemic circulation begins.
The circulatory system distributes oxygen-rich blood throughout the body. The ventricle pumps blood through the aorta, a massive artery that branches throughout the body. Once oxygen is delivered to the organs and limbs, it is returned through the veins, which lead it to the inferior vena cava or superior vena cava. Then from these two main veins it enters the right atrium. Once there, the oxygen-depleted blood returns to the pulmonary circulation.
The heart is a complex pump and the main organ of the circulatory system, ensuring the enrichment of the body with oxygen.
The heart is made up of chambers: atrium and ventricle. One on each side, each with different functions. The left side provides systemic circulation, while the right side of the heart is responsible for pulmonary circulation, that is, for oxygenation.
Atria
The atria are the chambers through which blood enters the heart. They are located on the front side of the heart, with one atrium on each side. The right atrium receives venous blood through the superior vena cava and the inferior vena cava. The left one receives oxygenated blood from the lungs through the left and right pulmonary veins.
Blood flows into the atrium, bypassing the valves. The atria relax and dilate as they fill with blood. This process is called diastole fibrillation, we are with you we call it pulse. The atria and ventricles are separated by the mitral and tricuspid valves. The atria pass around atrial systole, creating brief atrial contractions. They, in turn, push blood from the atria through the valves and further into the ventricles. The elastic tendons that attach to the ventricular valve relax during ventricular systole and move into ventricular diastole, but the valve closes during ventricular systole.
One of the defining characteristics of the atria is that they do not interfere with venous blood flow to the heart. Venous blood entering the heart has very low pressure compared to arterial blood, and the valves absorb the venous blood pressure. Atrial systole is incomplete and does not block the flow of venous blood through the atria into the ventricles. During atrial systole, venous blood continues to flow continuously through the atria into the ventricles.
The atrial contractions are usually minor, only preventing the significant back pressure that prevents venous blood from flowing. The relaxation of the atria is coordinated with the ventricle to begin to relax before the ventricles begin to contract, which helps prevent the pulse from becoming too slow.
Ventricles
The ventricles are located at the back of the heart. The ventricle receives blood from the right atrium and pumps it through the pulmonary vein into the pulmonary circulation, which enters the lungs for gas exchange. It then receives oxygen-rich blood from the left atrium and pumps it through the aorta into the systemic circulation to supply the body’s tissues with oxygen.
The walls of the ventricles are thicker and stronger than those of the atria. The physiological loads that pump blood throughout the body from the lungs are much greater than the pressure created to fill the ventricles. During ventricular diastole, the ventricle relaxes and fills with blood. During systole, the ventricle contracts and pumps blood through the semilunar valves into the systemic circulation.
People are sometimes born with congenital anomalies, in the form of a single ventricle with two atria. Rudimentary parts of the ventricular septum may be present but not functional. The disease is called heart disease.
The only species of amphibian that has 4 chambers of the heart is the common crocodile. A number of animals have three chambers, that is, two atria and one ventricle.
- amphibians
- amphibians
- reptiles.
In nature, amphibians and most reptiles have a prechamber heart and consist of two atria and one ventricle. These animals also have separate chains of blood vessels, where separate chambers are responsible for oxygen saturation, and the venous chamber returns and flows into the right atrium. From there, blood is conducted to the ventricle and then pumped to the lungs. After being enriched with oxygen and freed from carbon dioxide, the blood returns to the heart and flows into the left atrium. Then it enters the ventricle a second time and is further distributed throughout the body.
The fact that these are cold-blooded animals, their bodies do not expend much energy to produce heat. Thus, reptiles and amphibians can survive with less efficient heart structures. They also capable of blocking the flow in the pulmonary artery to divert blood to the skin for cutaneous respiration during diving. They are also capable of shunting blood flow in the pulmonary artery system during a dive. This anatomical function is considered the most complex among cardiac structures in vertebrates.
All vertebrate animals such as fish, amphibians, reptiles, birds, and mammals use oxygen from the air (or dissolved in water) to effectively extract energy from food and emit carbon dioxide as a waste product.
Any organism must deliver oxygen to all organs and collect carbon dioxide. We know that this specialized system is called the circulatory system: it is made up of blood, it contains cells that carry oxygen, blood vessels (the tubes through which blood flows), and the heart (the pump that pumps blood through the blood vessels).
Although everyone thinks that fish only have gills, it is worth noting that many species also have lungs. In many fish, the circulatory system is a relatively simple cycle. The heart consists of two contractile chambers, the atrium and the ventricle. In this system, blood from the body enters the heart and is pumped through the gills, where it is enriched with oxygen.
To answer the question of how this phenomenon appeared, we must first understand what was behind the formation of such a complex shape of the heart and circulatory system during evolution.
About 60 million years, from the beginning of the Carboniferous period until the end of the Jurassic period, amphibians were the dominant land animals on the ground. Soon, due to their primitive structure, they lost their place of honor. Although among the various families of reptiles that descended from amphibians, isolated groups were more resilient. For example, archosaurs (which eventually evolved into dinosaurs) and therapsids (which eventually evolved into mammals). The classic amphibian was the big-headed Eryops, which measured about fourteen meters in length from head to tail and weighed about two hundred kilograms.
Word "amphibian" in Greek means "both types of life", and that pretty much sums up what makes these vertebrates unique: they lay their eggs in water because they require a constant source of moisture. But they can live on land.
Great progress in the evolution of vertebrates has given many species circulatory and respiratory systems, highly efficient. According to these parameters, amphibians, amphibians and reptiles are located at the bottom of the oxygen-respiratory ladder: their lungs have a relatively small internal volume and cannot process as much air as the lungs of mammals. Fortunately, amphibians can breathe through their skin, which, coupled with a three-chambered heart, allows them, albeit with difficulty, to fulfill their metabolic needs.
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