CONTINUOUS RENEWAL AND REMOVAL OF FLUIDS
Secretory processes continuously renew the various fluid systems of the human
body. At the same time, the volume of fluid in each system is kept at a constant level
through the removal of excess fluids. Should the removal processes be interrupted, the
volume of fluid will increase. The resulting increase in pressure can have serious
consequences. Depending on the system involved, the consequences might include
deafness, hydrocephalus, or pulmonary edema.
COMPONENTS OF ANY CIRCULATORY SYSTEM
Any circulatory system has three general components:
a. Vehicle. The vehicle is a fluid (flowing) medium. The materials being
carried are dissolved or suspended in this fluid. This is the blood, lymph, or
b. Conduits. Conduits are like pipes. They contain the fluids in which
materials are transported to and from the various parts of the body. These are the
blood vessels or lymph vessels.
c. Motive Forces. Motive forces act upon the vehicle to make it flow through
the conduits. These are provided by the heart.
EXAMPLES OF CIRCULATORY SYSTEMS
Some circulatory systems of the human body are the cardio-vascular system,
the lymphatic system, and the CSF (cerebrospinal fluid) system. The lesser systems
include the aqueous humor of the bulbus oculi (eyeball) and the endolymph and
perilymph, which are fluids of the inner ear.
INTRODUCTION TO THE CARDIOVASCULAR SYSTEM
The cardiovascular system (Figure 10-1) is the primary circulatory system of the
human body. It includes a heart, blood, and blood vessels.
a. One function of the cardiovascular system is transport. Some substances
carried by the cardiovascular system are dissolved or suspended in the fluid portion of
the blood. Others are bound up in special cellular elements (RBCs).
b. The cardiovascular system also provides protection against foreign
substances. This function involves active attack by white blood cells as well as more
subtle processes of the immune system.