iii Have you ever wondered why you have curly, wavy, or straight hair? Or why you may have to wear corrective lenses for your eyes? Or why diseases strike some people but not others? Do you ever wonder if certain dietary and health habits might reduce your risk of having diabetes and coronary heart disease in later life? Did you know that it is important to maximize your bone density during early and teenage years to prevent developing osteoporosis? How can your lifestyle choices at 16 affect your body at 60? These are all considerations related to your anatomical and physiological makeup, and they are topics discussed in this book. People have been curious about the human body for centuries. It is quite natural, since it is the body you live in. The more you know and understand about your body, the more you can choose to make intelligent choices about your own health and longevity. Knowledge about these topics can also help you to help your family and friends understand their health issues. This textbook is your road map to understanding all of the fascinating intricacies of the human body. In addition to providing the basics of how your body works, the text highlights some of the latest research on topics of interest. Since many of you are probably curious about career opportunities in human health and healthcare, this text also features descriptions of job opportunities encompassing the ladder of jobs in healthcare. This textbook will answer questions you have had and raise other questions you may never have thought about. As you discover the answers on these pages, we believe you will agree with us that the human body is the most interesting topic in all of science. We wish you happy reading! Susan J. Hall Michelle A. Provost-Craig William C. Rose To the Student