Plasma makes up about 55 percent of the total blood volume.

a. Water. The major constituent of plasma is water. The physical characteristics of water make it a very good vehicle.

(1) Since water is fluid, it can flow through the conduits.

(2) Since most substances can be dissolved in water, it is often known as the "universal solvent."

(3) At ordinary pressures, water is essentially non-compressible.

(4) In addition, water has important temperature characteristics.

(a) Water has an ample heat-carrying capacity. It can carry heat readily throughout the body.

(b) Some of this heat is transferred to the water of the sweat glands. Since water can dissipate great quantities of heat through evaporation, excess heat can be efficiently disposed of at the surface of the skin.

b. Dissolved and Suspended Substances. To some extent, all transported substances are dissolved or suspended in the water of the plasma. These substances include various gases, end products of digestion, various control substances, and waste products. Also, there are three major plasma proteins--albumin, globulins, and fibrinogen. Together with dissolved salts (electrolytes), these plasma proteins help to maintain the tonicity of the plasma. In addition, fibrinogen is important to blood clotting.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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