This chapter provides basic information on human physiology and
anatomy as it relates to working in the underwater environment. Physiology is the
study of the processes and functions of the body. Anatomy is the study of the
structure of the organs of the body.
This chapter contains basic information intended to provide a fundamental
understanding of the physiological processes and functions that are affected when
humans are exposed to the underwater environment. A diver’s knowledge of
underwater physiology is as important as a knowledge of diving gear and procedures.
Safe diving is only possible when the diver fully understands the
fundamental physiological processes and limitations at work on the human body
in the underwater environment.
A body at work requires coordinated functioning of all organs and
systems. The heart pumps blood to all parts of the body, the tissue fluids exchange
dissolved materials with the blood, and the lungs keep the blood supplied with
oxygen and cleared of excess carbon dioxide. Most of these processes are
controlled directly by the brain, nervous system, and various glands. The individual
is generally unaware that these functions are taking place.
As efficient as it is, the human body lacks effective ways of compensating for
many of the effects of increased pressure at depth and can do little to keep its
internal environment from being upset. Such external effects set definite limits on
what a diver can do and, if not understood, can give rise to serious accidents.