Five Fast Facts
1. The heart is a muscular organ that beats 106,000 times each day, pumping 2,000 gallons of blood throughout the body.
2. The blood travels through 60,000 miles of blood vessels to deliver oxygen and nutrients to and pick up carbon dioxide and other waste products from all the tissues of the body.
3. Cholesterol, a waxlike substance normally found in the blood, has several important functions in the body.
4. Too much cholesterol in the blood can clog the arteries, impeding blood flow and preventing some tissues from getting enough oxygen.
5. If the blood vessels that supply oxygen to the heart or brain are clogged, you might have a heart attack or stroke.
Your doctor tells you that you have high cholesterol and you must change your diet, lose weight, and get more exercise. But you don't feel sick, and you like an occasional cheeseburger or bacon-and-egg breakfast, so what's the big deal? What does "high cholesterol" mean, anyway? How serious is it?
In a nutshell, high cholesterol means that, either because of your diet or your genetic makeup, you have too much cholesterol in your blood, and you run the risk of having a hew attack. For some people, just changing their diet and getting more exercise will bring the amount of cholesterol down to a safe level. Other people have high cholesterol levels because their bodies produce too much, and changing their diet will not reduce cholesterol levels enough. These people may need to take cholesterol-lowering drugs.
We will talk more about cholesterol levels and cholesterol-lowering drugs in later chapters, but fast, let's learn a little about the heart. To understand the consequences of having a high cholesterol level in the blood, one must first understand the workings of the heart and the importance of good blood flow.
The Heart and Blood Flow
The heart is a powerful organ that pumps blood throughout the body, ensuring that all of the organs and tissues get the oxygen they need to function properly. It seems miraculous once you understand how the heart works: It is a self-sufficient pumping station that keeps chugging away, supplying the body with oxygen and nutrients. It generates its own electrical signals, which cause the heart muscle to contract and push the blood out into the arteries and ultimately throughout the body. The heart then relaxes and draws up the blood that has already delivered oxygen to the body. And the heart just keeps going and going, beating about 100,000 times every day to pump 2,000 gallons of blood throughout the body in 60,000 miles of blood vessels. Providing adequate blood flow for a wide range of daily activities is a lot of work, even for a strong muscle like the heart. During exercise, the heart has to work even harder. It is very important, therefore, to keep your heart and blood vessels in good working order so your heart can perform its vital function--supplying blood to the body.
Anatomy of the Heart
The heart is a strong muscle about the size of your fist and is made up of four chambers surrounded by strong muscle. The heart can be divided into two sides, the right heart and the left heart. On each side the smaller chamber, called the atrium, sits on top of the larger chamber, called the ventricle. Atrium is the Latin word for "anteroom" or "porch," which aptly describes what the two atria do: They act as holding chambers for blood that will then be moved into the ventricles. Ventricle is the Latin word for "cavity" or "pouch" The atrium and ventricle on each side of the heart are connected by a small opening in which a one-way valve controls the direction of the flow. With normal valve function blood ran flow only from the right atrium into the right ventricle, not the other way around (likewise for the left atrium and left ventricle).
Blood flows in a continuous circuit through the body, stopping only briefly in the heart before it is pumped forcefully back out into the body. The right side of the heart receives the blood coming back from the body and pumps it to the lungs. The left side receives the blood from the lungs and pumps it back out into the body. Over and over again, the blood returns to the heart, is pumped to the lungs, returns to the heart, and is pumped into the body.
The blood coming into the right heart is low in oxygen, because it is returning from the body, and the blood coming into the left heart is high in oxygen, because it has just been in the lungs. It would not do, therefore, to have the blood in the right and left sides of the heart mix--the mixture would be too low in oxygen. The right and left heart are separated, therefore, by a band of tissue called the septum which prevents blood from flowing from the right atrium to the left atrium or vice versa (likewise for the ventricles).
Blood flow through the heart. Deoxygenated blood that has made its circuit through the body enters the right atrium of the heart and then flows through the right ventricle. The blood passes into the lungs, where it receives fresh oxygen. The freshly oxygenated blood enters the left atrium of the heart and then flows into the left ventricle. Blood then passes into the aorta and its branches, which brings blood into every comer of the body. Both of these circuits of blood flow through the heart simultaneously and continuously.
