Open circulatory system VS Closed circulatory system
1. Open Circulatory System:
In this system, the heart pumps fluid into an open space that surrounds the organs.
• How it works: Instead of staying in veins, the fluid (called hemolymph) leaves the vessels and "bathes" the organs directly. Imagine pouring water over a sponge—the organs just soak up what they need.
• Pressure: The pressure is very low. Because the fluid isn't confined to pipes, it moves slowly.
• Examples: Insects (like grasshoppers), spiders, and most mollusks (like snails).
2. Closed Circulatory System:
In this system, the blood never leaves the "pipes." It is always contained within the heart and blood vessels.
• How it works: The heart pumps blood through arteries, which branch into tiny capillaries. These capillaries are where nutrients and oxygen pass through the thin walls to reach cells. The blood then returns to the heart through veins.
• Pressure: The pressure is high. Since the blood is squeezed through narrow tubes, it can travel much faster and over longer distances.
• Examples: Humans, all other mammals, birds, fish, and even earthworms.