beginning of the venous vessels. However, a large percentage of the tissue fluid is
picked up by another circulatory system, the lymphatic system. Thus, there is a
continuous flow of the fluids throughout the body. In addition, the intracellular fluid and
the immediate extracellular fluid are continually being exchanged.
Section III. HOMEOSTASIS
a. The body fluids play an important role in homeostasis. Homeostasis is the
body's tendency to maintain a steady state. The tissue fluid forms the immediate
environment of the living cell. In order to maintain the life processes of the individual
cells, there must be appropriate concentrations of oxygen, carbon dioxide, nutrients,
electrolytes, and other substances within the tissue fluid.
b. One of the chief functions of any organ system is to help to maintain this
steady state. For example, the digestive system helps to maintain a steady
concentration of nutrients. The respiratory system helps to maintain steady
concentrations of oxygen and the removal of carbon dioxide.
c. All organ systems are at least partially controlled by a feedback mechanism.
A feedback mechanism resembles the household thermostat. When the concentration
of a substance is too low, the feedback mechanism stimulates an increased production
and/or distribution. Once the level returns to normal, the feedback mechanism signals a
decrease in production. There is a similar feedback mechanism for body temperature.
2-11. WATER BALANCE
The body has a natural requirement for a certain amount of water to continue its
processes properly. Lack of fluid in the circulatory system can result in heart failure.
Excessive amounts of fluid in the tissue spaces cause swelling of the body, known as
edema. There are feedback mechanisms to maintain water balance.
2-12. ELECTROLYTE BALANCE
The electrolytes must also be in balance. Electrolyte balance is an important
consideration when fluids are administered to a patient. See Figure 2-3 for an
explanation of tonicity.