Every day, the approximately 10 pints 5 liters of blood in your body travel many times through about 60, miles 96, kilometers of blood vessels that branch and cross, linking the cells of our organs and body parts.
The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries. Our bodies actually have two circulatory systems: The pulmonary circulation is a short loop from the heart to the lungs and back again, and the systemic circulation the system we usually think of as our circulatory system sends blood from the heart to all the other parts of our bodies and back again.
The heart is the key organ in the circulatory system. As a hollow, muscular pump, its main function is to propel blood throughout the body. It usually beats from 60 to times per minute, but can go much faster when it needs to.
It beats about , times a day, more than 30 million times per year, and about 2. The heart has four chambers that are enclosed by thick, muscular walls. It lies between the lungs and just to the left of the middle of the chest cavity.
The bottom part of the heart is divided into two chambers called the right and left ventricles , which pump blood out of the heart. A wall called the interventricular septum divides the ventricles. The upper part of the heart is made up of the other two chambers of the heart, called the right and left atria pronounced: AY-tree-uh.
The right and left atria receive the blood entering the heart. The tricuspid valve separates the right atrium from the right ventricle, and the mitral pronounced: MY-trul valve separates the left atrium and the left ventricle.
Two other heart valves separate the ventricles and the large blood vessels that carry blood leaving the heart. Blood vessels carrying blood away from the heart are called arteries. They are the thickest blood vessels, with muscular walls that contract to keep the blood moving away from the heart and through the body. In the systemic circulation, oxygen-rich blood is pumped from the heart into the aorta.
This huge artery curves up and back from the left ventricle, then heads down in front of the spinal column into the abdomen. Two coronary arteries branch off at the beginning of the aorta and divide into a network of smaller arteries that provide oxygen and nourishment to the muscles of the heart.
From the right ventricle, the pulmonary artery divides into right and left branches, on the way to the lungs where blood picks up oxygen. As they get farther from the heart, the arteries branch out into arterioles pronounced: ar-TEER-ee-olz , which are smaller and less flexible. Blood vessels that carry blood back to the heart are called veins. They are not as muscular as arteries, but they contain valves that prevent blood from flowing backward.
Veins have the same three layers that arteries do, but they are thinner and less flexible. The terms superior and inferior do not mean that one vein is better than the other, but that they are located above superior and below inferior the heart.
A network of tiny capillaries connects the arteries and veins. In addition, waste products such as carbon dioxide are also removed by the capillaries. The circulatory system works closely with other systems in our bodies.
It supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body. Hormones — produced by the endocrine system — are also transported through the blood in our circulatory system. Did you ever wonder about the process behind your beating heart?
In the first phase, the ventricles contract this is called systole , pronounced: SIS-tuh-lee , sending blood into the pulmonary and systemic circulation. When the ventricles finish contracting, the aortic and pulmonic valves close to prevent blood from flowing back into the ventricles. Then the ventricles relax this is called diastole , pronounced: dye-AS-tuh-lee and fill with blood from the atria, which makes up the second phase of the cardiac cycle.
A unique electrical system in the heart causes it to beat in its regular rhythm. The sinoatrial pronounced: sy-no-AY-tree-ul or SA node , a small area of tissue in the wall of the right atrium, sends out an electrical signal to start the contracting of the heart muscle. These electrical impulses cause the atria to contract first; they then travel down to the atrioventricular or AV node , which acts as a kind of relay station.
At each body part, a network of tiny blood vessels called capillaries connects the very small artery branches to very small veins. The capillaries have very thin walls, and through them, nutrients and oxygen are delivered to the cells. Waste products are brought into the capillaries. Capillaries then lead into small veins. Small veins lead to larger and larger veins as the blood approaches the heart. Valves in the veins keep blood flowing in the correct direction.
Two large veins that lead into the heart are the superior vena cava and inferior vena cava. The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart. Once the blood is back in the heart, it needs to re-enter the pulmonary circulation and go back to the lungs to drop off the carbon dioxide and pick up more oxygen.
How Does the Heart Beat? One complete heartbeat is made up of two phases: The first phase is called systole pronounced: SISS-tuh-lee. This is when the ventricles contract and pump blood into the aorta and pulmonary artery. During systole, the atrioventricular valves close, creating the first sound the lub of a heartbeat. When the atrioventricular valves close, it keeps the blood from going back up into the atria. During this time, the aortic and pulmonary valves are open to allow blood into the aorta and pulmonary artery.
When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. These valves closing is what creates the second sound the dub of a heartbeat. The second phase is called diastole pronounced: die-AS-tuh-lee. This is when the atrioventricular valves open and the ventricles relax. This allows the ventricles to fill with blood from the atria, and get ready for the next heartbeat. To help keep your heart healthy: Get plenty of exercise.
Eat a nutritious diet. Reach and keep a healthy weight. If you smoke, quit. Your veins contain valves that help keep oxygen-depleted blood flowing toward your heart. When these valves fail, blood collects in the veins, which can cause them to bulge and become swollen or painful.
Varicose veins most often appear on the lower legs. A blood clot is when blood coagulates or clumps together to form a gel-like mass. This clot can get stuck in a blood vessel where it blocks the flow of blood. Blood clots can cause:. A heart attack happens when the flow of blood to part of the heart is blocked or when the oxygen demand of the heart exceeds the oxygen supply. A stroke is when a blood vessel that supplies the brain with oxygen and nutrients is blocked.
When this happens, cells in your brain begin to die off. Circulatory system issues are best treated as early as possible. Your doctor can help monitor your cardiovascular health, as well as your blood pressure and cholesterol levels.
Call or seek immediate medical attention if you experience signs of a heart attack or stroke. Signs of a heart attack can include:.
Signs of a stroke include:. Your circulatory system is made up of your heart and an intricate network of blood vessels. The purpose of this system is to keep all the cells in your body supplied with fresh oxygen and nutrients while removing carbon dioxide and other waste products. Several different types of conditions can affect your circulatory system. Many of these conditions involve some type of blood vessel blockage, which can lower oxygen delivery to vital organs.
There are steps you can take to keep your circulatory system as healthy as possible. Some key steps include getting regular exercise, eating heart-healthy foods, not smoking, and maintaining a moderate weight. Regular visits to your doctor can also help identify and treat any potential problems before they become more serious issues. Read this article in Spanish. Experts say there are a number of ways to make it easier to go to bed at a proper time, including when you exercise and when you eat.
Left bundle branch block is a condition in which there's slowing along the electrical pathway to your heart's left ventricle.
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