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The Heart

About Dr Abdul Hafeez Chaudhry

Tubular Circulation
In a general sense, a vessel is defined as a hollow utensil for carrying something: a cup, a bucket, a tube. Blood vessels, then, are hollow utensils for carrying blood. Located throughout your body, your blood vessels are hollow tubes that circulate your blood.
There are three varieties of blood vessels: arteries, veins, and capillaries. During blood circulation, the arteries carry blood away from the heart. The capillaries connect the arteries to veins. Finally, the veins carry the blood back to the heart.

If you took all of the blood vessels out of an average child, and laid them out in one line, the line would be over 60,000 miles long! An adult's vessels would be closer to 100,000 miles long!

Besides circulating blood, the blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. We measure heart rate, or pulse, by touching an artery. The rhythmic contraction of the artery keeps pace with the beat of the heart. Since an artery is near the surface of the skin, while the heart is deeply protected, we can easily touch the artery and get an accurate measure of the heart's pulse.

When we measure blood pressure, we use the blood flowing through the arteries because it has a higher pressure than the blood in the veins. Your blood pressure is measured using two numbers. The first number, which is higher, is taken when the heart beats during the systole phase. The second number is taken when the heart relaxes during the diastole phase. Those two numbers stand for millimeters. A column of mercury rises and falls with the beat of the heart. The height of the column is measured in millimeters. Normal blood pressure ranges from 110 to 150 millimeters (as the heart beats) over 60 to 80 millimeters (as the heart relaxes). It is normal for your blood pressure to increase when you are exercising and to decrease when you are sleeping. If your blood pressure stays too high or too low, however, you may be at risk of heart disease.


                                                          

It's All in the Lungs
Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart again. This is just one phase of the overall circulatory system.
The veins bring waste-rich blood back to the heart, entering the right atrium throughout two large veins called vena cavae. The right atrium fills with the waste-rich blood and then contracts, pushing the blood through a one-way valve into the right ventricle.
The right ventricle fills and then contracts, pushing the blood into the pulmonary artery which leads to the lungs. In the lung capillaries, the exchange of carbon dioxide and oxygen takes place. The fresh, oxygen-rich blood enters the pulmonary veins and then returns to the heart, re-entering through the left atrium. The oxygen-rich blood then passes through a one-way valve into the left ventricle where it will exit the heart through the main artery, called the aorta. The left ventricle's contraction forces the blood into the aorta and the blood begins its journey throughout the body.

The one-way valves are important for preventing any backward flow of blood. The circulatory system is a network of one-way streets. If blood started flowing the wrong way, the blood gases (oxygen and carbon dioxide) might mix, causing a serious threat to your body.

You can use a stethoscope to hear pulmonary circulation. The two sounds you hear, "lub" and "dub," are the ventricles contracting and the valves closing.