This lesson will focus on the basic components of a closed circulatory system and the advantages of a closed circulatory system. It will also provide examples of organisms that have closed circulatory systems.
The Circulatory System
We all have blood flowing through our body, but how does the blood get from your brain to your foot and back again? Well, the circulatory system is the main method for blood transportation within your body. This system is a complex highway of vessels, and its main purpose is to move blood and nutrients throughout your body. The circulatory system is also responsible for exchanging gases and removing waste products from your body. Although all circulatory systems have the same function, these systems can be categorized into two different types based on the structure and design of their vessels. The two different types of circulatory systems that you will encounter are open systems and closed systems.
Open Circulatory System
Although this lesson is on the closed circulatory system, let’s take a brief look at open circulatory systems so we can better understand the difference.Open circulatory systems are the more basic type of circulatory system. They’re referred to as open because blood is not contained within an enclosed circuit of vessels. Instead, blood flows from the heart through open-ended vessels and, when it reaches the end of the vessels, it flows directly over the tissues. While the tissues are bathed in blood, gas exchange occurs.
Blood then freely flows back into vessels that direct the blood back to the heart. Overall, you could describe an open circulatory system as being more free flowing and passive. There are many organisms that have open circulatory systems, including grasshoppers, snails and clams.
Closed Circulatory System
The closed circulatory system may be of particular interest to you because it is the type of system that humans have.
Unlike an open circulatory system, a closed circulatory system is more structured and controlled. The blood of a closed system always flows inside vessels. These vessels make up the plumbing circuit of the body and can be found throughout the entire body. This plumbing circuit can be broken down into three different types of vessels, or tubes, that transport blood throughout the body: arteries, capillaries and veins.The first type of vessel is the arteries, which are responsible for moving blood away from your heart and to your tissues.
When blood gets to the tissues it is contained within capillaries, which are very small vessels with thin walls. These thin walls make it possible for gas and waste exchange to occur between your blood and your tissues. The blood then leaves the capillaries and goes into the veins, which bring blood back to your heart.
As you already know, humans have a closed circulatory system. But did you know that we share this type of system with such animals as birds, cats, frogs and earthworms?
On the left you have the grasshopper with its open circulatory system, and on the right you have an earthworm with its closed circulatory system.
What’s different? In a closed circulatory system, the blood leaves the heart, travels in a closed circuit circle and re-enters the heart. In comparison, in an open circulatory system, blood leaves the heart through open-ended vessels and more passively flows back to the heart.So which type of circulatory system is better? Unfortunately, there is no real answer to this question because both types of systems have their advantages and disadvantages.
Advantages of a Closed Circulatory System
There are several important advantages for organisms that have a closed circulatory system rather than an open system. The closed circuit design of a closed circulatory system makes it possible for the organism to control where the blood is flowing with more precision and more efficiency.
The closed circuit also creates a larger amount of pressure, which allows the blood to travel farther distances. This results in organisms with closed circulatory systems being able to grow larger than organisms with open systems.The pressure in the closed system also makes it possible for the organisms to move blood more quickly throughout the body and supply oxygen to tissues more rapidly. This ability to get oxygen to tissue more quickly makes it possible for closed circulatory organisms to move their muscles more rapidly than open system organisms. The next time you make a quick movement, think about how fast and how far the blood had to travel to your muscles to make that movement possible, and be thankful to your closed circulatory system.
|In quiz at the end of the lesson