Coronary heart disease

Author: Cui Liang / Country: Mainland China
Publisher:
Publish Date: 2006-06-01
Features:
3. Why is the heart called a "pump"?
The heart is an empty-chambered organ composed of cardiac muscle tissue. It, along with the body's blood vessels, forms the circulatory system of the human body. Blood flows in a certain direction within this system in a continuous cycle, known as blood circulation. The primary function of blood circulation is to transport nutrients absorbed from food daily and fresh oxygen inhaled from the lungs to all tissues and cells in the body, enabling them to perform vital physiological functions. The heart is the driving force of blood circulation, much like a water-pumping "pump" in a machine that promotes the continuous circulation of water. It contracts and relaxes rhythmically day and night, propelling blood to flow endlessly through the body's vascular system, thereby maintaining the body's life activities. The speed at which the heart pumps blood is truly remarkable—it ejects blood at a velocity of 8 m/s. The heart also has an automatic function. When the body's activity level increases, it pumps more blood to meet the body's needs; when the body is at rest, it pumps less blood. If the heart, this central driving pump, stops beating, blood circulation would cease, and life activities would end.
5. How does blood circulate?
Based on the different paths blood takes in the body, circulation can be divided into systemic circulation and pulmonary circulation.
Systemic Circulation: When the heart contracts, the fresh blood in the left ventricle is first pumped into the aorta. It then flows through the aorta's branches to the capillaries of all parts of the body, delivering oxygen and nutrients to organs, tissues, and cells for substance exchange. It carries away metabolic waste and carbon dioxide, becoming deoxygenated blood, which is finally collected by the superior and inferior vena cava and returned to the right atrium. This circulation process is called systemic circulation, also known as the large circulation.
Pulmonary Circulation: The deoxygenated blood returned to the right atrium flows into the right ventricle and is then injected into the pulmonary artery. It travels through the pulmonary artery to the pulmonary capillaries, where gas exchange occurs. After fully absorbing oxygen and releasing carbon dioxide, the blood becomes oxygen-rich and bright red. It is then returned to the left atrium by the pulmonary veins. This circulation process is called pulmonary circulation, also known as the small circulation. The blood that has undergone pulmonary circulation reaches the left atrium and is pushed into the left ventricle, which then pumps it into the aorta to be distributed throughout the body, continuing this cycle. Thus, systemic circulation and pulmonary circulation are connected through the heart, together forming the circulatory system. As a result, the lungs and heart have a close relationship. P2-3