Day 2: The Heart of the Matter

What is the Circulatory System and What Does It Do?

The circulatory system is like a circular network of roads on which traffic travels in only one direction. Every part of the body is connected through the network of blood vessels making up the circulatory system. The blood flowing in these vessels is composed of blood cells floating in a fluid called plasma.

Red blood cells possess a chemical called hemoglobin, which is responsible for carrying oxygen from the lungs to the individual cells of the body. Why do cells need oxygen? In return, the hemoglobin trades its oxygen for carbon dioxide, a waste product of the cell, and carries it back on its circular route to the lungs to be expelled.

The fluid portion of the blood, the plasma, is responsible for carrying all other nutrients (water, electrolytes, food, etc.) to the cells and in return, removing wastes. The plasma also carries chemical messengers, such as hormones, from the cells that produce and store the chemical messenger to the cells that it affects.

The circulatory system also acts as a cooling and heating system to maintain body temperature. Also, the circulatory system helps to maintain a balance of electrolytes and water between the cells and their environment.

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