REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Anatomy and Physiology includes an introduction to the human body, the chemistry of life, cells, the skin, the skeletal system, the skeletal muscles, the nervous system, the sense organs, the endocrine system, the circulatory system, the respiratory system, the digestive system, the urinary system, the reproductive system, and human development.