Blood vessels are an integral part of the circulatory system. These components assist in the transportation of blood within the body, often in and out of the heart. There are three basic types of blood vessels: the capillaries, which exchange water and chemicals between the blood and tissues; the arteries, which carry blood away from the beating heart and the veins, which transport blood from the capillaries to the heart, thus enabling the heart to continue beating.
Although blood vessels do not actively transport blood, the arteries and veins help to regulate blood by contracting the muscle layer of their inner diameter. This action is regulated by the autonomic nervous system and results in the flow of blood to downstream organs. Oxygen, which is attached to the hemoglobin in red blood cells, is the most essential nutrient transported by the blood vessels. Generally, hemoglobin in the arteries is highly saturated with oxygen--typically 95 to 100 percent--although it is only 75 percent saturated in veins. Veins and arteries are the largest components of the blood vessels. While arteries move the oxygenated and nutrient-rich blood to muscles and organs, veins carry the blood back to the heart.
The primary components of blood vessels--arteries, arterioles, capillaries, venules and veins--serve a variety of functions in keeping the body alive and healthy. These functions include transporting blood away from the heart, transporting oxygenated blood across the body, transporting blood from the arteries to the capillaries, draining blood from the capillaries into the veins and exchanging oxygen, carbon dioxide, water and salt between the body and surrounding tissues. Arterioles are also the main regulators of blood pressure and flow. Capillaries also assist in supplying the body's tissues with the necessary components of blood.
The Role of Blood Vessels in Disease
Blood vessels are an essential component in nearly every medical condition. Cancer is unable to progress or spread unless the tumor enacts angiogenesis, or the formation of need blood vessels. These vessels are necessary to provide the malignant cells' metabolic needs. Atherosclerosis, or the creation of lumps of lipids in the blood vessels, is also the primary cause for cardiovascular disease. Blood vessels are also vulnerable during inflammation. If the body is damaged due to trauma, for example, the body may begin to hemorrhage as a result of blood vessel damage.
A recent study completed by the University of Maryland School of Medicine in Baltimore suggests that laughter helps to keep blood vessels healthy and stable. Using laughter-provoking methods--including television shows and movies--to provoke their participants, scientists discovered that laughter seems directly linked to healthy and normal blood vessel function. By laughing, patients cause the tiny tissues on the inner lining of blood vessels (called endothelium) to dilate and expand, contracting with an increase in blood flow. This action proves to have a powerful effect on the blood vessels tone, and it assists in adjusting coagulation and blood thickening, regulating blood flow, and secreting the necessary chemicals and nutrients to fight off infection or irritation in the body.
Capillaries, essential components of blood vessels, are extremely tiny and narrow structures. Scientists estimate that these components are approximately 5 to 20 micrometers in diameter, or 0.000001 meters. In addition, scientists report that if all of the blood cells within an average human's body were laid end to end, the length would encircle the earth twice---a distance of nearly 100,000 kilometers.