The cardiovascular system, also known as the circulatory system, is composed of blood, blood vessels and the heart. The heart functions as a pump to move blood through the blood vessels of the body. A circulatory system is essential for large, multi-cellular organisms, such as humans and animals, and provide at least five major functions that are necessary for life.
Transporting Oxygen and Removing Carbon Dioxide
One of the most important functions of the circulatory system is to supply oxygen to all the cells in the body. Every cell in the body requires a constant supply of oxygen to stay alive. Because most of the cells are not in contact with air, the circulatory system must supply them with oxygen.
When a person inhales, air enters the lungs, and oxygen is then absorbed across the membrane of the lungs into the bloodstream. This oxygen-rich blood is pumped through the heart to smaller and smaller blood vessels throughout the body. In the tiniest blood vessels, called capillaries, oxygen diffuses out of blood and into cells. At the same time, carbon dioxide produced by the cells is absorbed back into blood, which then returns to the lungs, releases carbon dioxide and picks up more oxygen.
When a person inhales, air enters the lungs, and oxygen is then absorbed across the membrane of the lungs into the bloodstream. This oxygen-rich blood is pumped through the heart to smaller and smaller blood vessels throughout the body. In the tiniest blood vessels, called capillaries, oxygen diffuses out of blood and into cells. At the same time, carbon dioxide produced by the cells is absorbed back into blood, which then returns to the lungs, releases carbon dioxide and picks up more oxygen.
Transporting Nutrients and Removing Wastes
A second critical function of the circulatory system is to supply all the cells in the body with nutrients and energy. After food is digested in the stomach, it migrates through the intestines, where nutrients from food are absorbed into the bloodstream. The blood also absorbs glucose, an energy source, from the liver, which is the body's glucose distribution center. These nutrients and energy are then transported to all the cells of the body, in a manner similar to the transport of oxygen. Blood also absorbs the waste products made by cells, and transports them to the excretory organs for removal from the body.
Fighting Disease
In addition to nutrients and oxygen, the blood also carries around important disease-fighting cells. The organs of the immune system, such as the spleen, create many types of specialized cells that can kill foreign cells trying to invade the body. The circulatory system is responsible for transporting these cells from the immune system to all other parts of the body.
Transporting Hormones
Hormones are crucial chemical signals that the body uses to communicate with itself. Hormones control many things such as growth, the reproductive cycle and glucose metabolism. Hormones are created in one part of the body, such as the brain or the liver, and then must be transported to another part of the body by the cardiovascular system in order to deliver their message.
Regulating Body Temperature
The cardiovascular system also plays a role in regulating body temperature. If body temperature rises too high, blood vessels close to the skin dilate, increasing in size. The larger surface area of blood vessels close to the skin means more heat is conducted across the skin into the air. Conversely, if body temperature drops, the blood vessels constrict, decreasing in size. The smaller surface area of blood vessels next to the skin causes less heat to be lost across the skin and retains more heat in the body.
References
- CencerIndex.org: The Cardiovascular System
- Clinton College: Circulatory System
- Virginia State Department of Health: Care of the Circulatory System
- National Digestive Diseases Information Clearinghouse: Your Digestive System and How it Words
- Georgia State University: Temperature Regulation of the Human Body
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