The Cardiovascular System

Blood! Yuck!!

The Structures & Functions of the Cardiovascular System

The structures of the cardiovascular system are the heart, blood vessels, and the blood. The function of the cardiovascular system is to deliver nutrients to the body and remove byproducts from the tissues.

How the Blood Flows Through the Body

The blood flows through the body by the systemic and the pulmonary circuit. The pulmonary circuit is a “loop”, in which oxygenated blood travels through the lungs. The systemic circuit transports the rest of the blood in a loop through the body.

Different Types of Blood Vessels

There are three types of blood vessels, arteries, veins, and capillaries. Arteries are blood vessels that carry blood away from the heart. They are the thickest blood vessels, with muscular walls that contract to keep the blood moving away from the heart and through the body. Veins are blood vessels that carry blood back to the heart. 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 two largest veins are superior and inferior. Even though capillaries are tiny, they're the most important parts of the circulatory system, because through them nutrients and oxygen are delivered to the cells. Also, capillaries help get rid of waste products such as carbon dioxide.
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Blood Cell Formation

Blood cells form in the bone marrow where all blood cells originate from a stem cell. When a stem cell divides, at first it becomes an immature red blood cell, white blood cell, or platelet-producing cell. Then the immature cell divides, matures further, and ultimately becomes a mature red blood cell, white blood cell, or platelet.

Human Blood Groups

  • Group A – has only the A antigen on red cells (and B antibody in the plasma)
  • Group B – has only the B antigen on red cells (and A antibody in the plasma)
  • Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma)
  • Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)
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Diseases and Disorders of the Cardiovascular System

Three common cardiovascular diseases and disorders are heart failure, arrhythmia, and heart attack.

  • A heart attack happens when blood flow to the heart has decreased or stopped, because the coronary arteries start to harden and narrow from the build-up of fat, cholesterol, and other substances that are all known as plaque. A blood clot forms around the plaque, blocking blood flow. This results in permanent damage or death of part of the heart muscle.
  • Arrhythmia is a change in the way the heart beats. It is in the electrical impulses of the heart—not the arteries or blockages. These electrical impulses may happen too fast, too slow, or irregularly, which causes the heart to beat the same way. When the heart doesn’t beat normally, it can’t pump blood effectively to the lungs, brain, and other organs, causing them to potentially shut down or become damaged.

  • Heart failure is when the heart’s ability to pump is weaker than normal. Blood moves through the heart and body at a slower rate, pressure increases in the heart, and the heart can’t supply enough blood and oxygen to the body’s cells, resulting in fatigue and shortness of breath.