Circulation of the Blood

THE CIRCULATION OF THE BLOOD: Double Circulation of the Blood (through the lungs & through the body) showing the path of oxygen and carbon dioxide.

Double Circulation of the Blood refers to the passage of the blood firstly through the lungs (the pulmonary circulation - where it picks up oxygen and releases carbon dioxide) and then through the body (the systemic circulation) where it delivers its cargo of oxygen and picks up carbon dioxide. These two circuits are powered by different sides of the heart. The right side of the heart pushes the blood at relatively low pressure through the lungs. The left side of the heart pushes the blood at relatively high pressure through the whole body.

The system of vessels and the Heart is known as the cardiovascular system. The heart is really a highly specialized segment of vessel that is muscular and supplied with valves (heart valves) to create the one way flow of blood. In the heart, the two sides are joined and the complex plumbing of vessels makes the flow rather difficult to understand.

BLOOD FLOW THROUGH THE HEART

1. deoxygenated blood returning from the body enters the heart through the superior vena cava and inferior vena cava.

2. blood passes into the right atrium and right ventricle

3. right ventricle pushes the blood through the pulmonary arteries

4. blood passes through the lungs where it loses carbon dioxide and picks up oxgen

5. this oxygenated blood returns to the heart via the pulmonary veins

6. blood enters the left atrium and left ventricle

7. the left ventricle pushes the blood out through the main artery, the aorta

8. blood travels to all parts of the body where it delivers oxygen and picks up carbon dioxide

It's All in the Lungs

Pulmonary Circulation: It's All in the Lungs

Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart again. This is just one phase of the overall Circulatory System.

The veins bring waste-rich blood back to the heart, entering the right atrium throughout two large veins called vena cavae. The right atrium fills with the waste-rich blood and then contracts, pushing the blood through a one-way valve into the right ventricle. The right ventricle fills and then contracts, pushing the blood into the pulmonary artery which leads to the lungs. In the lung capillaries, the exchange of carbon dioxide and oxygen takes place. The fresh, oxygen-rich blood enters the pulmonary veins and then returns to the heart, re-entering through the left atrium. The oxygen-rich blood then passes through a one-way valve into the left ventricle where it will exit the heart through the main artery, called the aorta. The left ventricle's contraction forces the blood into the aorta and the blood begins its journey throughout the body.

The one-way valves are important for preventing any backward flow of blood. The circulatory system is a network of one-way streets. If blood started flowing the wrong way, the blood gases (oxygen and carbon dioxide) might mix, causing a serious threat to your body.

You can use a stethoscope to hear pulmonary circulation. The two sounds you hear, "lub" and "dub," are the ventricles contracting and the valves closing.

human body, the lungs