In this lesson, you will learn to differentiate between a closed and an open circulatory system. Read on, and you will be able to characterize the earthworm’s circulatory system!
Open versus Closed Circulatory Systems
If you are wondering what type of circulatory system an earthworm has, it is important to first understand that there are two main types of circulatory systems: open and closed.
The circulatory system in animals – regardless of type – functions to provide nutrients and get rid of wastes, but what is the difference between an open and a closed system? The answer is actually very simple: vessels.
Closed Circulatory System
In a closed circulatory system, blood is contained within vessels, and will never leave the vessel system. These vessels originate from the heart, which is the pump of the circulatory system.
Try putting your hand to your chest to feel your heart beating; what you are actually feeling is the pumping action of the heart that moves blood through your vessels.
Blood circulates unidirectionally from the heart through arteries, arterioles, and capillaries, to reach all tissues and organs in the body. The capillaries are very narrow vessels with a one-cell layer-thick wall, which allows the easy transfer of nutrients and oxygen from the blood to cells.In addition, cells dump carbon dioxide and wastes back into the blood, which returns to the heart through venules and veins. This closed system is found in all vertebrates and some invertebrates.
Open Circulatory System
In an open circulatory system, the blood is not contained within a vessel system.
Instead, tissues and organs are surrounded by the circulatory fluid, which is known as hemolymph. Hemolymph is like blood and includes interstitial fluid, which is the fluid that usually surrounds tissues.
|From very simple cnidarian, the hydra. Hydras are