From Cells to Organism Help (page 2)

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By — McGraw-Hill Professional
Updated on Aug 30, 2011


In line above the tissues are the organs. An organ is a collection of two or more of the basic body tissues, which together perform some special function. The heart, for instance, is an organ with special muscle in its thick walls that allows it to carry out the function of pumping the blood. The heart contains connective tissue valves in its chambers, which are lined with modified epithelial cells. And various nerves supply the heart wall, serving either to speed it up or slow it down, whenever particular conditions arise.

Organ Systems

An organ system is a collection of two or more organs, which together perform some complex body function. Consider the cardiovascular ( kar -dee-oh- VA -skew-lar) or circulatory ( SIR -kyew-lah- tor -ee) system. (Examine Figure 2.4.) The cardiovascular (circulatory) system mainly involves the “heart” (cardi) and its attached blood “vessels” (vascul), through which the blood is pumped in a “little circle” (circul). The complex function performed by this system is the carrying of blood and its contained nutrients (such as oxygen and glucose) towards the body tissues, followed by the removal of waste products (such as carbon dioxide) from the body tissues.

Patterns of Life Cells to Organism: Where the Pyramid Comes to Life Organ Systems

Fig. 2.4 An overview of the cardiovascular (circulatory) system.


Practice problems for these concepts can be found at: Patterns of Life Test

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