This document provides an introduction to the structure and function of the human body. It discusses the levels of organization from the chemical level to organ systems. The four main tissue types are described as nervous, muscle, epithelial and connective tissues. Anatomical terminology including body positions, planes, and directional terms are outlined. Homeostasis is introduced as the maintenance of a stable internal environment through feedback control systems that detect changes and trigger responses to correct deviations from normal ranges.