"The human circulatory system is essential for pumping blood throughout a person's body. Without it, humans wouldn't be able to live. This guide to a basic biology concept explores the main elements of the circulatory system, introduces key parts such as blood vessels and the heart, examines problems with this system, and offers a comprehensive review of one of the most complex parts of the human body. Complete with fact boxes and . . . sidebars, accessible language, discussion questions, and descriptive photographs and diagrams, this introduction will appeal to readers at a variety of levels"--Provided by publisher.