There are four separate chambers in our own hearts. Frogs, toads, snakes and lizards have only three. The heart of vertebrates performs the function of pumping the body's blood throughout the body. Similar in many respects, these organs have different numbers of chambers in different classes of vertebrates. What are the structural features of the circulatory system and heart of the frog?
Classification
Depending on the number of chambers, vertebrate hearts can be classified as follows:
- Two-chamber: one atrium and one ventricle (in fish).
- Three-chamber: two atria and one ventricle (in amphibians and reptiles).
- Four chamber: two atria and two ventricles (in birds and mammals).
Functions
What is a heart and why is it needed? Its most important function is to pump blood through the circulatory system. Since this organ is really just a pump and does not have any other functions, one might think that in different animals it looks and functions.the same, but it's not.
Instead, nature creates new forms as animals evolve and change their needs. As a result, there are many hearts in terms of structure. They all perform the same job, namely, they pump circulating fluid through the circulatory system. Let's take a look at the different types of vertebrate hearts and how they evolved.
Two-chambered heart
All vertebrates have a closed circulatory system with one central heart. The oldest type is the two-chamber type, which some modern fish still have. It is a very muscular organ, consisting of one atrium and one ventricle. The atrium is a chamber that receives blood returning to the heart. The ventricle is the cavity that pumps blood out of the heart.
These two departments are separated by one one-way heart valve. The device ensures that the blood only travels in one direction, out of the ventricle and into the blood vessels, where it makes one loop through the circulatory system. Further, the blood is distributed to the gills (the respiratory organ in fish), which take oxygen from the surrounding water. The oxygen-rich blood then flows through the tissues and finally returns to the heart.
Three-chambered heart
The double chambered heart has served fish well for a very long time. But amphibians have evolved and landed, and their circulatory system has undergone significant evolutionary changes. They have developed dual circulation and now have two separate blood flow patterns.
One circuit, called the pulmonary circuit, leads to the respiratory organs to create oxygenated blood. As a result of double circulation, a three-chambered amphibian heart is formed, consisting of two atria and one ventricle. The second circuit, called the systemic circuit, carries oxygenated blood to various tissues in the body.
The structure of the frog's heart also suggests the presence of three chambers. Blood passes first through the pulmonary chain, where it is oxidized, and then returns to the heart through the left atrium. It then enters the left side of the common ventricle, and from there most of the oxygen-rich blood is pumped in a systemic fashion to distribute oxygen to the tissues before it is returned to the right atrium.
The blood then flows to the right side of the normal ventricle (before it is pumped back into the lung chain). Because the ventricle shares both circuits, there is some mixing of oxygen- and carbon-dioxide-rich blood. However, it is reduced due to the presence of a ridge in the center of the ventricle, which somewhat separates its left and right sides.
Four-chambered heart
Once the three-chambered heart evolved, the logical next step in evolution was to completely separate the ventricle into two separate chambers. This could ensure that the oxygenated and carbonated blood from the two circuits would not mix. This evolutionary progression between three- and four-chambered hearts can be seen in different types of reptiles.
The heart of amphibians and reptiles is usually three-chambered. In different typesthere are walls of various sizes that partially separate the ventricle. The only exception are some species of crocodile, which have a complete septum. They form a four-chambered organ, similar to that of birds and mammals, including humans.
Different hearts: pulmonary and systemic circulation
Blood contains many elements, from nutrients to waste products. One vital substance, oxygen, enters the blood through the gills or lungs. To achieve its effective use, many vertebrates have two separate circulations: pulmonary and systemic.
Let's look at the four-chambered human heart. In the pulmonary circulation, this important organ sends blood to the lungs to take in oxygen. Blood appears in the right ventricle. From there, it enters the lungs through the pulmonary arteries. Further, the blood goes through the pulmonary veins and moves into the left atrium. The blood then enters the left ventricle, where the systemic circulation begins.
Systemic circulation is when the heart distributes oxygenated blood throughout the body. The left ventricle pumps blood through the aorta, a massive artery that supplies all parts of the body. Once oxygen reaches the tissues, blood returns through the various veins. The entire venous network leads to the inferior or superior vena cava. These vessels go to the right atrium of the heart. The oxygen-depleted blood is returned to the lungs.
By keeping these two circulations separate, the four-chambered heart optimizes oxygen utilization. Onlyoxygen-rich blood enters the body. Only blood containing carbon dioxide goes to the lungs. Birds and mammals have four chambers. Probably the dinosaurs had the same structure. Crocodiles and alligators are similar, but they can shut off circulation to their lungs when underwater.
Structure of the heart
How many heart chambers does a frog have? This deep red colored conical muscular organ is centrally located in the anterior part of the body cavity between the two lungs. The frog's heart is three-chambered. It is enclosed in two membranes - the inner epicardium and the outer pericardium. The space between these layers is called the pericardial cavity. It is filled with pericardial fluid, which performs the following functions:
- protects the heart from mechanical damage;
- creates a humid environment;
- supports the frog's heart in the correct position.
External structure
What is the structural feature of the lake frog's heart? Outwardly, it looks like a triangular structure of a reddish color. Its anterior end is wide, while the posterior end is somewhat pointed. The anterior part is called the shell, while the posterior part is called the ventricle. Shells are two-chambered: left and right atrium. They are demarcated externally by a very weak longitudinal inter-risk depression. The ventricle is single chamber. This is the most important part of the heart. It has a conical shape with thick muscular walls and is clearly separated from the atria by the coronal sulcus.
Internal structure
What is the inner circuitry of a frog's heart? The wall of the organ consists of three layers:
- outer epicardium;
- medium mesocardium;
- internal endocardium.
The inner heart is 3-chambered with two shells and one ventricle separated by a septum. The right shell is larger than the left, it has a transverse oval opening, called sinuoricular. Through it, blood enters the right shell. The opening is protected by two lip flaps called sino-auricular valves. They allow blood to flow to the right but prevent back flow.
There is a small opening in the pulmonary vein in the left atrium next to the septum, which has no valves. The left concha receives blood from the lungs through the pulmonary veins. The ventricle has a thick muscular and spongy wall with numerous longitudinal fissures separated from each other by muscular projections. Both turbinates open into the same chamber of the ventricle via the auriculoventricular orifice, which is guarded by two pairs of auriculoventricular valves. The valves are equipped with chords that pull the flaps back to close the hole and thus prevent backflow of blood.
Structure and work of the heart of a frog
The heart of amphibians, like any other animal, is a muscular organ that acts as a pumping station. It is located in the center in the front region of the body. A heartreddish in color and triangular in shape with a broad anterior end. The external and internal structure of the frog differs significantly from the structure of the body of other amphibians, however, there is a similarity of some internal organs.
Frogs have a heart: a look at the circulatory system
Have you ever felt a frog's heartbeat or pulse? If you look at the diagram of the circulatory system of this amphibian, you will notice that its structure is significantly different from ours. Deoxygenated blood is sent to the atrium from various organs of the frog's body through blood vessels and veins. It is drained from the organs and thus the purification process begins. Oxygenated blood then enters from the lungs and skin and travels to the left atrium. This is how gas exchange occurs in most amphibians.
Both atria dump their blood into one ventricle, which is divided into two narrow chambers. Thanks to this system, the mixing of oxygenated and deoxygenated blood is reduced. The stomach contracts, sending O2 rich blood from the left ventricle. It reaches the head, flowing through the carotid arteries. This is almost pure blood, which is what the brain receives.
The blood passing through the aortic arches is mixed, but there is still a lot of oxygen in it. This is enough to supply the rest of the body with what it needs. The internal and external structure of the frog and other amphibians differ significantly from underwater inhabitants such as fish, andalso from land animals such as mammals.
Is it possible for the heart to work outside the body?
Surprisingly, the frog's heart will continue to beat even if it is removed from the body, and this applies not only to amphibians. The reason lies in the organ itself. There is a special conducting system of neuromuscular nodes in which impulse excitation spontaneously arises, spreading from the atria to the ventricles. This is why the work of the frog's heart outside the body continues for some time after it has been removed from the body.
