Function of the Circulatory System

The circulatory system provides oxygen to cells in the body

The trillions of cells in your body require a continuous supply of oxygen and nutrients to carry out their vital functions, but cells can use these substances only when they are in the immediate vicinity. Like a busy factory that delivers its products to various stores, your body must have a transportation system to carry its gasses and nutrients to its various cells. This system is called your circulatory system, and in this lesson, you will learn about the different parts of the circulatory system and how these parts help move needed substances throughout your body.

To illustrate, let's take a look at Mr. Smith's Widget Factory. Mr. Smith's factory is a very busy place. His factory runs 24 hours a day, 365 days a year. Mr. Smith's workers must work hard to keep up with the continual demand for his widgets; if his workers quit working, his business would not survive. Even though Mr. Smith's factory is very busy, it is nothing compared to the non-stop activity going on in your body at this very minute. Every second of every day, trillions of cells in your body pick up nutrients and drop off waste.

Parts of the Circulatory System

In the same way that Mr. Smith's employees use roads to get his products to and from stores, your body usesblood vessels, which are hollow tubes for carrying blood. The blood found within your blood vessels is a fluid that transports oxygen, nutrients, and cell wastes throughout your body. Keep in mind that these vital substances must make their way to every cell in your body. As you can imagine, this is a very big job. In fact, if laid end to end, all of the blood vessels in the human body would travel around the earth two and a half times. It seems hard to believe, but because the blood vessels have to carry blood to so many cells in your body, your body contains roughly 62,000 miles of blood vessels.

62,000 miles of blood vessels are in the human body

Mr. Smith uses trucks that run on gasoline to get his widgets where they need to be. Your body does not run on gasoline; instead, it relies on a pumping station known as your heart, which is a hollow organ that pumps blood through the blood vessels. Your heart is the ultimate workaholic, and the amount of work it does is almost too hard to believe. In one 24-hour period your heart pumps your body's complete supply of blood - about 6 quarts - through the blood vessels over 1000 times. Good thing your heart does this for you without your conscious input, or you wouldn't get much else done. The heart, along with the miles of blood vessels found throughout your body, make up your circulatory system, which is defined as a closed system of blood vessels for the transport of gasses and nutrients.

Back at Mr. Smith's factory, we see that his truck drivers have returned from making their deliveries. Now is a good time for us to take a closer look inside Mr. Smith's factory to see just how he runs such an efficient operation. Mr. Smith's factory is divided into two separate departments. So distinct are the goals of the two departments that it's easier for us to think of Mr. Smith's factory as two factories in one. The factory on the right is responsible for piecing together the widgets. In the right factory, widgets pick up their needed parts, and unneeded parts are discarded. The factory on the left takes the freshly-made widgets and transports them all over the country.

Just as it is easier for us to think of Mr. Smith's factory as two factories in one, it is easier for us to think of the circulatory system as two circuits in one. Because we learn about the body in anatomical position, we look at this picture of the heart as if it is inside a person who is facing us. Therefore, the right side of the heart is here, seen in blue, and the left side is here, seen in red. The right side of the heart is the pulmonary circuit, and the left side is the systemic circuit.