blood circulates through the body
at a temperature of 38.0øC (100.4øF). This is slightly higher
than the body temperature as determined by mouth. An adult of
average age and size has just over 5.7 liters (6 quarts) of
blood.
Blood is a complex fluid because of the fragments of cytoplasm that are suspended within the fluid. It is classified as a connective tissue because it contains cells separated by a fluid matrix. It is a characteristically red, mobile fluid with an average specific gravity of about 1.058. Slightly sticky, blood has a viscosity between 4.5 and 5.5 times greater than that of water at the same temperature. Thus, blood flows somewhat more sluggishly than water. The odor of blood is characteristic; the taste is slightly saline. The pH of blood ranges between 7.35 and 7.45.
Under normal conditions, blood circulates through the body
at a temperature of 38.0øC (100.4øF). This is slightly higher
than the body temperature as determined by mouth. An adult of
average age and size has just over 5.7 liters (6 quarts) of
blood.
In very general terms, blood serves as a chemical transport
and communication system for the body (i.e., it carries chemical
messengers as well as nutrients, wastes, etc.). 
Circulated by the
heart through arteries, veins and capillaries, blood carries
oxygen and a variety of chemicals to all cells. Blood also takes
away waste products, including carbon dioxide, from the various
tissues to organs such as the kidneys or lungs which ultimately
dispose these wastes to the environment.
Unlike a simple liquid or a simple solution,
blood is a
complex fluid made up of several components each of which is
extremely complex.