"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 intriguing sidebars, accessible language, discussion questions, and descriptive photographs and diagrams, this introduction will appeal to readers at a variety of levels"--.