Under the action of the heart pump, the blood flows in the heart andVascular systemIt flows again and again.It includes systemic circulation and pulmonary circulation, which are interconnected to form a complete circulatory system.
Chinese name
blood circulation
Foreign name
blood circulation
Form
Closed loop
Composition
Systemic and pulmonary circulation and coronary circulation
When the ventricles contract, bright red blood (arterial blood) containing more oxygen and nutrients outputs from the left ventricle, passes through the aorta and its branches at all levels, reaches the capillaries in all parts of the body, and conducts material exchange and gas exchange in the tissue. The blood becomes purplish blood (venous blood) containing tissue metabolites and more carbon dioxide, and then passes through veins at all levels,Finally, it flows into the superior and inferior vena cava and returns to the right atrium.The blood circulation of the above path is called systemic circulation, also called grand circulation.The main characteristics of systemic circulation are long journey, wide flow range, nourishing all parts of the body with arterial blood, and transporting metabolites and carbon dioxide back to the heart.
（2） Pulmonary circulation
From the right ventricle, the venous blood with less oxygen and more carbon dioxide will pass through the pulmonary artery to the capillary network around the alveoli, where it will exchange gas with the alveoli, that is, the venous blood will emit carbon dioxide (exhale from the lung), and at the same time, it will inhale oxygen from the alveoli, thus turning the dark red venous blood into bright red arterial blood (with more oxygen and less carbon dioxide),Through all levels of pulmonary veins, it finally flows into the left atrium.The blood circulation of the above path is called pulmonary circulation, also called small circulation.The pulmonary circulation is characterized by a short distance, only passing through the lungs, mainly converting venous blood into oxygen rich arterial blood.
（3） Coronary circulation
Coronary circulation is to provide the heart with the nutrients and oxygen it needs and transport waste.It is a circulation in which the blood flows directly from the coronary artery at the base of the aorta to the capillary network inside the myocardium and finally from the vein back to the right atrium.
Circulating energy
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The flow of blood requires energy, which is mainly generated by heart beating, and the energy of heart beating is ultimately generated by mitochondria in cells, so the content of mitochondria in myocardial cells is quite large.Mitochondria are the places where energy is generated. The activities in mitochondria are mainly the second and third stages of aerobic respiration, which can be divided into three stages:
The first stage: glucose dehydrogenation, producing reducing hydrogen, pyruvate and a small amount of ATP. This stage is carried out in the cytoplasm matrix.
The second stage: Pyruvate continues to dehydrogenate, and water molecules are required to participate in the reaction to produce reducing hydrogen, carbon dioxide and a small amount of ATP.
The third stage: the hydrogen removed in the first two stages combines with oxygen to generate water, which generates a large amount of ATP.ATP is also called adenosine triphosphate and adenotriphosphate. It is mainly the combination of adenine and ribose to form adenosine. Adenosine is formed by combining the fifth hydroxyl group in ribose with three connected phosphate groups. When ATP acts, it removes one phosphate to form ADP, which will release energy.
physiological function
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The main significance of blood circulation is to ensure the metabolism of the body.Various tissues of animal body obtain various nutrients, water and oxygen from blood, and use these substances for oxidation to generate heat energy to ensure normal function;At the same time, waste products such as carbon dioxide, urea and uric acid generated by metabolism are discharged into the blood, transported to the respiratory organs and excretory organs respectively, and discharged out of the body, so as to keep the physical and chemical properties of the tissue relatively constant.In addition, hormones secreted by endocrine glands are transported to all parts of the body through circulation to regulate the physiological function of the body.
