Introduction

Biology is a broad term used for the study of life and all living organisms. The term ‘biology’ is derived from the Greek words ‘Bios’ (βίος) which means ‘life’, and ‘Logos’ (λόγος) which means ‘study’. There are many different branches of biology including cell biology (study of cell structure and function) which revolves around the concept that the cell is the fundamental unit of life. The cell as a fundamental structure can be combined to form tissues and organs and the study of these (as a single cell or a group) is known as anatomy and physiology. Anatomy and physiology are typically discussed together however they focus on separate aspects of life. Anatomy refers to the physical structure of an organism, such as humans or bacteria and the relationship between these structures. Physiology on the other hand, focuses on the function of these structures. Homeostasis refers to a state of balance among all the body systems needed for the body to survive and function correctly. The goal of homeostasis is the maintenance of equilibrium around a specific value of some aspect of the body or its cells called a set point. While there are normal fluctuations from the set point, the body’s systems will usually attempt to go back to this point. A change in the internal or external environment is called a stimulus and is detected by a receptor; the response of the system is to adjust the activities of the system, so the value moves back toward the set point.

Body organs and organ systems constantly adjust to internal and external changes to maintain this steady state. Examples of internal conditions maintained homeostatically are the concentration of blood glucose (sugar), body temperature, or blood calcium level, to name only a few. These conditions remain relatively stable because of physiologic processes that result in negative feedback relationships. If blood glucose or calcium concentrations rise, this sends a signal to organs responsible for lowering blood glucose or calcium concentrations to return to the homeostatic set point. A more noticeable homeostatic regulation is the maintenance of core body temperature or thermoregulation. If body temperature drops, this stimulus causes a number of changes in the body, from muscle contractions (shivering) to peripheral blood vessel constriction (to minimise loss of heat from the blood through the skin). The signals that restore the normal levels are examples of negative feedback. When homeostatic mechanisms fail, the results can be unfavourable for the body. Homeostatic mechanisms keep the body in dynamic equilibrium by constantly adjusting to the changes that the body’s systems encounter and even when seemingly inactive, the body is maintaining this homeostatic equilibrium.

However, before learning about the parts of the body, their physical structures, what they do or how they work, the correct use of medical terminology needs to be explored. In this chapter, some directional terms and planes of view used in anatomy and physiology will be presented together with some common roots, prefixes and suffixes to start to become familiar with the new language regarding the body.