Circulatory System

Bianca Otarola

June 7th, 2013

6th period

The Circulatory System

        The circulatory system consists of the heart, blood, and blood vessels. Its function is to transport gases, like oxygen from the lungs to cells, and carbon dioxide from cells to the lungs. They transport nutrients like glucose, and also transport waste from cells to organs that eliminate them. The circulatory system includes cells that fight infections and foreign bodies. It helps maintain pH, fluid levels, and body temperature (especially in endothermic animals). There are two types of circulatory systems: an open system, and a closed system. 

        An open system is a circulatory system where blood is not contained in blood vessels, for example, crayfish. They're common to most mollusks and arthropods. They pump blood so that the blood is diffusing back to the circulatory system between cells. The blood is pumped by the heart into the body cavities, where the blood surrounds the tissue (http://www2.gsu.edu/~bioasx/closeopen.html). A closed system is where blood is contained in blood vessels, for example, humans. The structures included in a closed circulatory system include the heart, blood, and blood vessels. Most vertebrates and a few invertebrates have a closed circulatory system. In a closed system, the blood is closed at all times. In this system, blood is pumped by a heart through vessels, and doesn't normally fill body cavities.

        Open circulatory systems make it more difficult for oxygen to be filtered in and out. The limits to diffusion cause organisms with open circulatory systems to have a slower metabolic rate  (http://answers.yahoo.com/question/index?qid=20090112234110AAlPAIT). Closed circulatory systems require a rather stronger heart because there's more energy to maintain, and it's more complex, but more efficient and powerful.