Todays topic for ICSC biology class 6 is Structure and Function of a Heart . To check the part 1 for this chapter click on this link.
Blood Circulatory system in humans and Worksheets for Science related to this topic
Circulatory system in human beings consist of heart ,blood and blood vessels. The components and functions of blood are discussed in the part 1 of this chapter. In this part 2 of this chapter we will discuss about the heart and the blood vessels. This chapter has three parts. Links for part 1 and part 3 are provided in this article.
What are blood vessels?
The hollow tube like structures that carry blood from one part of the body to the other parts are known as blood vessels. These are of three types-
1.Arteries
2.Veins
3.Capillaries
1.Arteries - These are muscular an pipe like structures. Their wall is thick and they possess elasticity. They carry oxygen rich or oxygenated blood from the heart to various parts of the body. They are seated deeply inside the body.
Pulmonary artery - Pulmonary artery is the exception which carries impure or deoxygenated blood to the lungs.
2.Veins - These are thin walled vessels that carry deoxygenated blood from various parts of the body to the heart.
Pulmonary Veins - These are the exception as they carry pure or oxygenated blood from the lungs to the heart. Blood in these veins flow under low pressure smoothly. They consist of valves that stop the back flow of bloodblood and lie close to the skin.
3.Capillaries - Arteries and veins are connected through the capillaries. They help in the exchange of gases and nutrients.
Structure and Function of a Heart
It is a muscular organ and is pear shaped. It is found towards the left side of the human body. Heart is protected inside the rib cage. The size of the heart is like that of a clenched fist. The muscles that constitute the wall of the heart are known as cardiac muscles. Heart is protected inside a tough sac called pericardium which further consists of two layers. It encloses a fluid known as the pericardial fluid between these two layers and protects the heart from injuries. The heart consists of four chambers. The upper two chambers are known as auricles and the lower two chambers are known as ventricles.
Auricles - These are the upper two chambers of the heart. They receive blood from various parts of the body.The impure or deoxygenated blood is received by the right auricles from the various parts of the body. The pure or oxygenated blood from the lungs is received by the left auricles.
Ventricles - These are the lower chambers of the heart. The left ventricle receive oxygenated or pure blood from the left auricle while the right ventricle receive impure or deoxygenated blood from the right auricle.
The right auricle is separated from the right ventricle by the tricuspid valve. The left auricle is separated from the left ventricle by the bicuspid valve.
How blood is circulated in the blood?
The deoxygenated blood from various parts of the body goes to the right auricle. The right auricle pushes it to the right ventricle.From the right ventricle it moves to the lungs through the pulmonary artery which carries deoxygenated blood. In the lungs, the blood gets oxygenated by the exchange of gases. This oxygenated blood moves to the left auricle through the pulmonary veins. The left auricle pushes it to the left ventricle. This blood then moves to the aorta which is the largest artery in the body. The aorta divides to form a number of arteries that carry this blood to various parts of the body. This blood supplies nutrients and gases to various parts of the body through capillaries and collect waste materials and CO2 from various parts of the body. Hence it becomes deoxygenated and impure and again moves to the right auricle.
What is double circulation?
In this process, the heart passes from the blood two times to complete one cycle or round of circulation. It occurs in two steps -
1.Pulmonary Circulation - In this process the circulation of blood takes place between the heart and the lungs.
2.Systematic Circulation - In this process, the circulation of blood takes place between the heart and various parts of the body.
What is heart beat and cardiac cycle?
All the heart muscles are not contracted at the same time. Firstly, the contraction of auricles take place. This pushes the blood to the ventricles. Just after that, the ventricles contract and pushes the blood to the aorta and the pulmonary artery.The blood again flows to the auricles from vena cava and the pulmonary veins as the auricles relax. Soon after that the ventricle get empty and the heart is relaxed.
The contraction of the heart is known as systole while the relaxation of the heart is known as diastole. This contraction and relaxation completes a single round or circle of circulation of blood.The sequence of events that occur during a single or one round of circulation is known as the cardiac cycle.
A throbbing sound produced during the contraction and relaxation of the heart is known as the heart beat.It includes a lub dub type of sound.he sound produced during the contraction of the auricles is weak while the sound produced during the contraction of ventricles is strong.
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To check the part 3 of this chapter click on this link : https://lessonstobelearneda-z.blogspot.com/2022/03/pulse-and-blood-pressure.html
Note : If you want to follow the chapter only then justfollow the links provided for the part 01 of the chapter on the top. You may skip the external links given in between the article.
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