open and closed circulatory system

• Blood is a life-giving liquid that circulates throughout the body, going to every corner to bring in food and oxygen and take away waste products.
• Blood flows through blood vessels, which are long tubes through which the blood flows.
• The blood vessels never open up, they're always closed, which is why it's called a closed circulatory system.
• The heart, a muscular organ which pumps blood, releases blood under pressure so that the blood can go to all the parts of the body.
• The heart pumps blood into the blood vessels and the blood flows through these blood vessels.
• The blood vessels subdivide to form very fine small blood vessels called capillaries.
• Capillaries, being so small and fine, can reach all the parts of the body, namely the tissues.
• Capillaries supply oxygen and nutrients to the interstitial fluid which surrounds the tissues and take back waste products and carbon dioxide.
• The blood in insects bathes the tissues and then returns to the heart through tiny pores called ostia.
• The metabolic rates of insects are much lower than humans, allowing them to survive with a less efficient circulatory system.
• Human beings are highly active animals with metabolic rates that are high as compared to some other animals.
• The circulatory system of insects is open, allowing the blood to diffuse from one part of the body to another.
• The blood is scattered throughout the body of the animal and finds its way back into the heart.
• Insects have a heart, blood vessels, and a circulatory system similar to humans.
• The circulatory system of insects is less efficient but less energy consuming due to the lower metabolic rates of these small and simple animals.
• In insects, the blood and the interstitial fluid are one and the same thing, which is also called hemolymph.
• Insects do not need as many nutrients or as much oxygen as humans due to their lower metabolic rates.
• The drawback of the open circulatory system is the large amount of energy expended.
• The blood, having supplied material to all the tissues of the body through the diffusion that is taking place between the interstitial fluid and the blood in the capillaries, goes back to the heart through some other blood vessel.
• Capillaries join again to form these bigger blood vessels which are actually the veins.
• The blood vessels coming from the heart are the arteries and then these are the veins which carry blood back to the heart, this is how blood circulates throughout the human body through the closed circulatory system.
• In the human body, five to six liters of blood go through the entire body in less than 20 seconds, covering a distance of nineteen thousand kilometers, making the closed circulatory system incredibly efficient.
• The efficiency of the closed circulatory system is due to the powerful heart, a muscular organ which pumps blood at a huge force, pushing the blood throughout the body so fast.