|
|
 The red fluid that flows through all vessels except the lymph vessels
is called blood. Blood is a viscous fluid, it is thicker and more
adhesive than water. Water is considered to have a viscosity of
1. The viscosity of blood by comparison, ranges from 4.5 to 5.5.
This means that it flows 4 1/2 - 5 1/2 times slower than water.
The adhesive quality of blood, or its stickiness, may be felt by
touching it. Blood is also slightly heavier than water.
Other physical characteristics of blood include temperature of
about 38*C (100.4* F), a ph range of 7.35 to 7.45 (which makes blood
slightly alkaline, similar to the ph of ocean water) and a 0.85
to 0.90 percent concentration of salt. (NaCl, sodium chloride) Blood
constitutes about 8 percent of the total body weight. The blood
volume of an average sized male is between 5 and 6 liters (5 to
6 quarts). The average sized female has 4 to 5 quarts.
Despite its simple appearance, blood is a complex liquid that performs
a number of critical functions:
- It transports oxygen from the lungs to all cells
of the body.
- It transports carbon dioxide from the cells to
the lungs.
- It transports nutrients from the digestive organs
to the cells.
- It transports waste products from the cells to
the kidneys, lungs and sweat glands.
- It transports hormones from endocrine glands to
the cells.
- It transports enzymes to various cells.
- It regulates body ph through buffers and amino
acids.
- It plays a role in the regulation of normal body
temperature because it contains a large volume of water, which
is an excellent heat absorber and coolant.
- It regulates the water content of cells, principally
through dissolved sodium ions.
- It prevents body fluid loss through the clotting
mechanism.
- It protects against toxins and foreign microbes
through special combat-unit cells. (gee...they don't specify,
but could these be natural killer cells??)
Microscopically, blood is composed of two portions; plasma, which
is a liquid containing dissolved substances, and formed elements,
which are cells and cell-like bodies suspended in the plasma.
Source: Principles of Anatomy and Physiology, (third edition, p.
442) Tortora & Anagonstakos, Harper & Row, New York, 1981.
|
