Compare & Contrast Open & Closed Circulatory Systems

Instructor: Margaret Cunningham

Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.

In this lesson, you will explore open and closed circulatory systems. You will also learn what these two systems have in common and what makes them different.

Circulatory Systems

Think about all of the roads you travel on every day. Although roads vary in size and structure, from highways to dirt roads, they all make it possible for you to move from one place to another. Similarly, your body also has a complex network it uses to transport materials within your body. The circulatory system is a combination of vessels and organs that are used to transport blood and nutrients throughout an organism. Organisms come is all different shapes and sizes and also have different types of circulatory systems. Animals can have either a closed system or an open system.

Closed Circulatory System

Before we explore the details of the closed circulatory system, it is important to know that this is the type of circulatory system you have! Closed circulatory systems are referred to as closed because the blood in the system flows within a complex network of vessels, or tubes, that are all connected to each other. The blood is pumped by a heart throughout the body in a continuous circuit of different types of vessels. Due to the fact that a closed circulatory system creates higher pressure in the blood vessels, organisms with this type of circulatory system are able to grow larger because the body can push blood greater distances. In addition to humans, many other organisms have closed circulatory systems including cats, dogs, birds, and earthworms.

Closed Circulatory System
Closed circulatory system

Open Circulatory System

The second type of circulatory system that we are going to examine is the open circulatory system. This system is much less complex than the closed system. Although an open circulatory system also contains a heart to pump the blood, not all of the vessels are connected to each other. The open system gets its name because there are gaps or opening between different vessels. In an open system the blood flows out of vessels, surrounds tissues for exchange of nutrients, and then passively returns to vessels to be moved to a different part of the body. The open circulatory system is common in smaller organisms, such as grasshoppers, clams, and snails, which do not require blood to be moved as far as larger organisms.

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