Located in plant cells are large irregular shaped green structures called chloroplasts. They are green because they contain a green pigment called chlorophyll.
An open circulatory system is a type of circulatory system in which nutrients and waste are moved through the body with the assistance of a fluid which flows freely through the body cavity, rather than being contained in veins.
A closed circulatory system is a circulatory system where blood is contained within vessels. The purpose of these blood vessels is really not much different from the purpose of water pipes in a city, which is to transport a necessary commodity long distances and distribute it to many locations.