The circulatory system, composed most notably of the heart and blood vessels, is responsible for sending oxygenated and nutrient-rich blood to body cells. Because the system is largely mechanical in nature—the heart acts like a pump, and the vessels like pipes to move fluid—many complications of the circulatory system are mechanical in nature. Blockages of vessels and compromised ability of the heart to pump blood represent significant mortality risks.
Atherosclerosis
Perhaps one of the most common circulatory problems, at least in the United States, is atherosclerosis, or hardening of the arteries. MayoClinic.com explains that this process begins when a diet high in cholesterol and saturated fat—or a genetic predisposition to high blood cholesterol—leads to the formation of hard plaques inside artery walls. This stiffens the arteries and decreases their resilience, which is quite dangerous, since the arteries are the first vessels off the heart, and must withstand the flow of high-pressure blood with each heartbeat. As blood flows through damaged arteries, it can cause the plaques to crack or rip, leading to bleeding and formation of a clot. Small clots can then break off, travel through the bloodstream, and become lodged in small vessels elsewhere. If clots get trapped in the blood vessels of the brain, the result is a stroke; clots in the blood vessels of the heart, on the other hand, result in a heart attack.
Mitral Valve Prolapse
The heart is designed to be a one-way pump; blood enters the left side of the heart as it returns from the lungs in a fully oxygenated state, and is pumped via the heart’s left side to the body cells. As deoxygenated blood returns from the body cells, it enters the heart’s right side, and is pumped back to the lungs. This circular flow keeps blood from backtracking, and prevents deoxygenated blood from getting to the body cells, which would lead to cellular oxygen debt. In order to maintain circular blood flow, they heart utilizes a system of valves. The largest of these, the mitral valve, keeps blood ready to leave the heart and travel to the body from being regurgitated into pulmonary circulation. The book “Anatomy and Physiology” notes that in some individuals, the mitral valve may prolapse, or collapse on itself. This results in varying amounts of blood regurgitation and decreases the efficiency of the heart. Mitral prolapse is more common in women than men, and is one of the most frequent causes of a “heart murmur,” or indistinct heartbeat.
Deep Vein Thrombosis
If blood clots form in the large veins returning blood to the heart—particularly the veins of the legs—they can prevent appropriate blood return and lead to cardiovascular malfunction or even stroke. The National Heart Lung and Blood Institute notes that individuals with damaged vein linings or those who have slow blood flow may be particularly at risk for deep vein thrombosis—this includes post-surgical patients and those confined to bed or a chair for long periods of time. Excessively thick blood, too, may increase the risk of deep vein thrombosis, for which reason pregnant women are advised not to sit for long periods without standing to stretch the legs. Pregnancy increases the thickness of the blood, and regular standing and stretching augments venous return, preventing deep vein thrombosis.
References
- MayoClinic.com: Atherosclerosis
- “Anatomy and Physiology”; Gary Thibodeau, Ph.D.; 2007
- National Heart Lung and Blood Institute: Deep Vein Thrombosis
