The sino-atrial node is called the pacemaker of our heart. Due to this, the heart is known as myogenic.ġ0. All these groups of animals exhibit double circulation and hence there is no mixing of oxygenated and deoxygenated blood.Īns: The normal activities of our heart are autoregulated by specialized muscles known as nodal tissues. In cases of higher animals like aves, reptiles, and mammals, the heart further evolved out as a well-developed, 4-chambered structure with two atrium and two ventricles.
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In this type of heart, both the pureblood and impure blood get mixed in the ventricle. The fishes have a 2-chambered heart with an atrium and a ventricle, which then evolved into the three-chambered heart in amphibians and reptiles which have two atria and one ventricle. All of the vertebrates possess a muscular chambered heart. Describe the evolutionary change in the pattern of the heart among the vertebrates.Īns: A comparative study of the structures of hearts of vertebrates reveals that there is an evolutionary change in the pattern of heart among the vertebrates. (a) Differences between lymph and blood are:Ĩ. (b) Open and Closed system of circulation Significance of double circulation: In double circulation, complete separation of oxygenated and deoxygenated blood takes place which allows a more efficient supply of oxygen to the body cells. Then, the oxygenated blood from the lungs is carried by the pulmonary veins into the left atrium. (ii) Pulmonary circulation: Thi circulation involves the circulation of deoxygenated blood from the right ventricle to the pulmonary artery, which then carries blood to the lungs for getting oxygenated. From tissues, the deoxygenated blood is collected by a system of venules, veins, and vena cava, and is emptied into the right atrium. Then a network of arteries, arterioles, and capillaries supplies this oxygenated blood to various tissues in the body. (i) Systemic circulation: In this method, the circulation of oxygenated blood takes place from the left ventricle of the heart to the aorta. This process involves two types of blood circulations: What is meant by double circulation? What is its significance?Īns: Double circulation- It is defined as the process in which blood passes 2 times through the heart during one complete cycle.
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It mainly helps in the transportation of respiratory gases and various nutrients inside the body.Ħ.
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It contains lymphocytes which are known to be responsible for the immune responses.