Life, clearly, is in the blood. As a transport mechanism for waste products, life-sustaining oxygen and nutrients, normal blood flow is essential to your health. That's why the different parts of your heart continuously beat in unison, receiving and distributing this precious fluid to the rest of your body, via a large system of blood vessels.
Pumps and Pipes
Your cardiovascular system works similarly to a hydraulic system in which your heart is a suction and pressure pump, and your blood vessels, the pipes. Your heart is divided into four chambers: two atria and two ventricles. The right and left atria are receiving chambers, which pump the blood they receive into your right and left ventricles. The ventricles then pump blood out to your organs, via your blood vessels. Your left heart essentially carries oxygenated and nutrient-rich blood to your various organs, while your right heart carries oxygen-poor blood coming from your organs.
Blood Vessels
There are three types of blood vessels: arteries, veins and capillaries. Arteries are thick-walled, muscular vessels that carry blood under high pressure away from the heart. In contrast, veins are thin-walled and carry blood back to the heart. The blood courses through arteries of decreasing size, ending in the smallest vessels called capillaries. Within the tissues of your body, capillaries form capillary beds where the exchange of oxygen, nutrients, and waste products occurs between incoming and outgoing blood. From the capillary bed, blood goes into small veins called venules, which drain into veins of increasing size.
The Aorta
When you inhale, the left side of your heart receives oxygen-rich blood via your lungs. The aorta is the largest blood vessel that carries oxygenated blood from your heart to the rest of your body. With a diameter approximately equal to your thumb, it arises from the left ventricle of your heart, at an opening called the "aortic orifice." Aortic semilunar valves separating the aorta's opening from that of the left ventricle open and close rhythmically to control the rate and direction of blood flow. The aorta gives off multiple branches that carry blood to different organs.
The Pulmonary Trunk
After the right side of your heart receives de-oxygenated blood from your organs, it pumps it towards your lungs for re-oxygenation via the pulmonary trunk. Because its structure resembles that of the aorta, anatomists describe the pulmonary trunk as an artery. It begins at an opening called the "pulmonary orifice of the right ventricle," and terminates by dividing into the right and left pulmonary arteries. In order to control blood flow, pulmonary semilunar valves separate the pulmonary trunk's opening from that of the right ventricle.
Cardiac Veins
As an organ, the heart not only receives oxygen-rich blood and nutrients for its own use, but it also gives off waste in oxygen-poor blood. A number of small veins carry de-oxygenated blood away from the heart chambers, to empty into a wide channel known as the coronary sinus. Several veins from different areas of the heart merge to form the main vein of the heart, or coronary sinus. These veins include the great cardiac, small cardiac, middle cardiac, left posterior ventricular and left marginal veins.
Considerations
Arteries owe their red appearance to the fact that, with the exception of the pulmonary trunk and arteries, they generally carry oxygen-rich blood. In contrast, your veins appear blue because they usually transport oxygen-poor blood, which is rich in carbon dioxide. The large pulmonary veins are an exception, since they carry well-oxygenated blood from the lungs to the heart.
References
- "Clinically Oriented Anatomy"; Keith Moore, Ph.D. and Arthur Dalley, Ph.D.; 2006
- "Hollinshead's Textbook of Anatomy"; Cornelius Rosse, M.D. and Penelope Gaddum-Rosse, Ph.D.; 1997
