1. The Heart

2. Blood is pumped through the blood vessels of the body by the contractions of the heart. Blood is pumped through the blood vessels of the body by the contractions of the heart. The heart has 4 chambers. The two upper chambers, the atria, receive blood returning to the heart from the rest of the body. The heart has 4 chambers. The two upper chambers, the atria, receive blood returning to the heart from the rest of the body.

3. The two lower chambers, the ventricles, pump blood out of the heart into the arteries. The walls of the ventricles are thicker and more muscular than those of the atria. The two lower chambers, the ventricles, pump blood out of the heart into the arteries. The walls of the ventricles are thicker and more muscular than those of the atria. The pericardium covers the heart and protects it. The pericardium covers the heart and protects it.

5. Circulation Through the Heart

6. The oxygen-poor or deoxygenated blood from the body is returned to the right atrium of the heart through two large veins. The oxygen-poor or deoxygenated blood from the body is returned to the right atrium of the heart through two large veins. One of these veins is from the upper part of the body and the other is form the lower part of the body. One of these veins is from the upper part of the body and the other is form the lower part of the body.

7. This deoxygenated blood flows down from the right atrium into the right ventricle. This deoxygenated blood flows down from the right atrium into the right ventricle. From there it is pumped out of the heart through the pulmonary arteries to the lungs. From there it is pumped out of the heart through the pulmonary arteries to the lungs. When in the lungs, the blood gives up CO2 and picks up oxygen. When in the lungs, the blood gives up CO2 and picks up oxygen.

8. This oxygenated (oxygen-rich) blood is then returned through the pulmonary veins to the left atrium of the heart. This oxygenated (oxygen-rich) blood is then returned through the pulmonary veins to the left atrium of the heart. The blood then passes from the left atrium into the left ventricle, which pumps it through the aorta, the largest artery in the body. The blood then passes from the left atrium into the left ventricle, which pumps it through the aorta, the largest artery in the body.

9. This one-way flow of blood through the heart is controlled by valves that prevent backflow of the blood. This one-way flow of blood through the heart is controlled by valves that prevent backflow of the blood. There are valves between the atria and the ventricles, between the right ventricle and the pulmonary artery, and between the left ventricle and the aorta. There are valves between the atria and the ventricles, between the right ventricle and the pulmonary artery, and between the left ventricle and the aorta.

10. Pathways of Circulation

11. The pathway of blood between the heart and the lungs is called the pulmonary circulation. The pathway of blood between the heart and the lungs is called the pulmonary circulation. The circulatory pathway between the heart and all other parts of the body except the lungs is called the systemic circulation. The circulatory pathway between the heart and all other parts of the body except the lungs is called the systemic circulation. The system of blood vessels that supplies the heart itself is called the coronary circulation. The system of blood vessels that supplies the heart itself is called the coronary circulation.

12. Disorders of the Transport System

13. Diseases of the heart and blood vessels are called cardiovascular diseases. The most common form of this is high blood pressure or hypertension, which is characterized by elevated blood pressure. Diseases of the heart and blood vessels are called cardiovascular diseases. The most common form of this is high blood pressure or hypertension, which is characterized by elevated blood pressure. Hypertension can damage the lining of arteries and weaken the muscle of the heart. Hypertension can damage the lining of arteries and weaken the muscle of the heart.

14. A blockage of the coronary artery or its branches is a coronary thrombosis, or heart attack. As a result of this blockage muscle tissue of the heart is deprived of oxygen and is damaged. A blockage of the coronary artery or its branches is a coronary thrombosis, or heart attack. As a result of this blockage muscle tissue of the heart is deprived of oxygen and is damaged.

15. A narrowing of the coronary arteries may cause temporary shortages of oxygen to the heart, resulting in intense pain in the chest or in the left arm or shoulder. This condition is known as angina pectoris. A narrowing of the coronary arteries may cause temporary shortages of oxygen to the heart, resulting in intense pain in the chest or in the left arm or shoulder. This condition is known as angina pectoris. A condition in which the blood can’t carry enough oxygen to the cells of the body is known as anemia. A condition in which the blood can’t carry enough oxygen to the cells of the body is known as anemia.

16. A form of cancer in which the bone marrow produces an abnormally large number of white blood cells is known as leukemia. A form of cancer in which the bone marrow produces an abnormally large number of white blood cells is known as leukemia.