Chapter 1

AN INTRODUCTION TO THE HUMAN BODY

Chapter Synopsis

This chapter presents the definitions and subdivisions of anatomy and physiology and the relationship between structure and function.  Students are introduced to the six levels of structural organization that comprise the body (chemical, cellular, tissue, organ, system, and organismic); components and functions of the principal body systems are then discussed.  The basic life processes are described with descriptive examples.  The concept of homeostasis as an underlying principle in the study of living systems is introduced and the body’s external environment is explained in terms of the dynamics of fluid movement between the extracellular and intracellular compartments.  The relative stability of homeostasis is contrasted with pathology, the outcome of homeostatic disruption.  Aging and its effects on homeostasis are discussed.  The roles of the nervous and endocrine systems in maintaining homeostasis are explained.  Feedback systems (loops) are defined, using the regulation of blood pressure as an example of negative feedback and the control of labor contractions as an illustration of positive feedback. Disease is discussed as disruption of homeostasis in varying degrees and symptoms of disease are distinguished from clinical signs.  Diagnosis is defined; the importance of a medical history and a physical examination in arriving at a diagnosis is explained.  The next section orients the student to the human body through topics such as anatomical position, regional names, directional terms, planes and sections, body cavities, and abdominopelvic regions and quadrants. Autopsy is discussed as a tool for gaining postmortem knowledge not only of cause of death, but also of factors previously affecting the living body.  The relationship between medical imaging and the diagnosis of disease is explained by comparing conventional radiography with newer imaging techniques.