How it Works
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The Circulatory System is one of the main organ systems in the human body. It allows the blood to circulate throughout the body to transport nutrients, oxygen, carbon dioxide, hormones and blood cells. It does this to help nourish cells which can then fight disease, stabilize body temperature, and sustain homeostasis. This system also includes the lymphatic system which returns excess blood plasma (yellow liquid of blood, that holds the blood cells) from between cells as lymph. Since humans are vertebrates, we have a closed circulatory system, meaning the blood never leaves the network of blood vessels. Although some invertebrate groups have an open circulatory system which means there is no blood or interstitial fluid, instead its combined into one called hemolymph, which the organs sit in and then carries out the same responsibilities.