This document provides an overview of human anatomy and physiology. It discusses the main levels of structural organization in the human body from the chemical level to the organismal level. It also defines anatomy and physiology, describing anatomy as the study of the body's structure and physiology as the study of its functions. The major organ systems are introduced, including descriptions of their structures and functions. Homeostasis and homeostatic control mechanisms are explained as the body's ability to maintain stable internal conditions through the interaction of receptors, control centers, and effectors in a negative feedback loop.