Blood Vessels Health Article

Role in human health

The 2001 "Heart and Stroke Statistical Update," published by the American Heart Association, states that cardiovascular diseases (CVD) have been the leading cause of death in the United States every year since 1900, with the exception of 1918. CVD accounted for 40.6% of all U.S. deaths in 1998; over 60 million Americans are estimated to suffer from one or more CVD.

There are numerous factors that increase the risk of cardiovascular disease. These include:

• Major risk factors: tobacco smoke, race, genes, diabetes mellitus, high cholesterol levels, hypertension, physical inactivity, and obesity.
• Contributing risk factors: stress, high triglycerides, alcohol, oral contraceptives, pregnancy, menopause, and Syndrome X (a cluster of risk factors that include obesity, glucose intolerance, hypertension, and high cholesterol).

Blood vessels and blood flow can respond to a variety of local control factors, including neural (such as shock) or hormonal impulses (such as anger or fear). Blood vessels themselves can also grow (a process called angiogenesis) or remodel themselves in response to diseases such as ischema and hypertension.

Common diseases and disorders

• Atherosclerosis: According to the American Heart Association, atherosclerosis accounts for nearly 75% of all cardiovascular-related deaths. It involves the accumulation of lipids and other substances on the inner lining of an artery; the area of buildup is called a plaque. As a result, the arterial wall thickens and hardens, losing elasticity. Thrombi (blood clots) form when plaques rupture; if these occlude the artery, a heart attack or stroke may result.
• Stroke: A stroke occurs when the brain has been deprived of oxygen due to interrupted blood flow, often caused by a blood clot or burst blood vessel. Depending on the area of the brain that is damaged, neurological damage may be reversible or irreversible and may include coma, paralysis, visual or speech problems, seizures, or impaired memory.
• Varicose veins: Permanent changes in the diameter and/or length of veins may result from damage to or failure of the venous valves. Gravity, obesity, pregnancy, and increasing age may also play a role in the development of varicose veins.
• Hemangiomas: These are usually benign vascular anomalies that may result in small, harmless birth-marks or sacs of vascular tissues of varying sizes that may protrude from the skin. Hemangiomas are often only cosmetic blemishes but may, depending on their location, cause obstruction of the airway, block vision, or obstruct a vital organ.
• Aneurysm: An aneurysm results from the dilation of the wall of a blood vessel due to the weakening of the wall by disease, high blood pressure, or congenital defects. An abdominal aortic aneurysm is the most common type. A ruptured aneurysm is a serious medical emergency and requires surgical intervention.

KEY TERMS

Anastomoses—Connections formed where arteries and arterioles merge to provide alternative channels for blood delivery.

Arteries—Blood vessels that carry blood away from the heart.

Diastolic pressure—Diastole is the period in which the left ventricle relaxes so it can refill with blood; diastolic pressure is therefore measured during diastole.

Hydrostatic pressure—Force per unit area exerted by a fluid (blood) against a vessel wall.

Lumen—The hollow center of a blood vessel.

Osmotic pressure—The pressure required to prevent osmosis of fluid across a semi-permeable membrane. It is an indirect measurement of the water and solute concentrations of the solution.

Systolic pressure—Systole is the period of the cardiac cycle in which the aortic valve opens and blood flows into the aorta; systolic pressure is the maximal pressure during systole.

Tunica intima, media, adventitia—The three layers that compose the walls of large arteries and veins.

Vasa vasorum—Small blood vessels that supply the walls of large arteries and veins with oxygen and nutrients.

Veins—Blood vessels that carry blood from the capillary beds to the heart.

BOOKS

Aaronson, Philip, et al. The Cardiovascular System at a Glance. Oxford, UK: Blackwell Sciences, Ltd., 1999.

Chang, John B., et al. Textbook of Angiology. New York: Springer-Verlag, 2000.

Diehm, C., et al. Color Atlas of Vascular Diseases. Berlin: Springer-Verlag, 2000.

Marieb, Elaine N. Essentials of Human Anatomy and Physiology. Boston: Benjamin Cummings, 2001.

PERIODICALS

"Cardiovascular Diseases." 2001 Heart and Stroke Statistical Update. American Heart Association, 2000.

ORGANIZATIONS

American Heart Association. 7272 Greenville Ave., Dallas, TX 75231. (800) AHA-USA1. <http://www.americanheart.org>.

Stephanie Islane Dionne