How Does Animal Circulatory Systems — Open vs. Closed Circulatory Work?

Imagine your body is like a busy city where messages and supplies need to get from one place to another, that’s what circulatory systems do in animals.

Some animals have an open circulatory system, like a snail. Think of it as a city with open streets where the mail truck (which is like blood) can roll right into the houses (the cells). The mail truck doesn’t stay inside one street, it spreads out and goes everywhere, delivering supplies to all the houses.

Other animals have a closed circulatory system, like you or your dog. It’s more like a city with highways, the mail truck stays on the road (inside blood vessels) and only drops off packages at specific stops (like the heart). The mail truck never gets out of the car, it just keeps moving along the roads, going from one stop to another.

In open systems, the blood mixes directly with body fluid. It’s like when you pour juice into a bowl, everything gets mixed together.

In closed systems, blood stays inside tubes (blood vessels). It's more like drinking juice through a straw, it doesn’t mix with anything else, just goes straight to your mouth.