Blood: Plasma and Cells That Sustain Life
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Blood: Plasma and Cells That Sustain Life

Blood contains plasma and cells that are vital to maintaining life. Learn about the functions of blood and why it's so important to the body.

Many people think of blood only when dealing with an injury when it leaks from a cut or puncture wound. Blood is the liquid of life and performs a variety of functions throughout the body. By looking at the different components of blood, it will be clear just how important this substance is to maintaining the life of the human body.

What is Plasma?

Blood is actually made up of both liquid and solid particles. The liquid portion of blood is called plasma. Plasma makes up approximately 55% of the total volume of blood and is made primarily of water. This liquid blood substance also contains chemicals that allow the blood to clot when injuries occur, and glucose, salts, and proteins which are used to help the body’s processes occur.

The solid portion of the blood is made up of cells. There are three primary categories of cells in the blood: white blood cells, red blood cells, and platelets. Each of these cells has specific properties which allow them to perform vital functions in the blood.

White Blood Cells

White blood cells are used for defense of the body from foreign invaders. These cells come in five different varieties and perform many defense functions of immunity and protection. White blood cells come in five varieties: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Depending on the foreign invader, a particular type of white blood cells will be called on to respond.

Red Blood Cells

Red blood cells are used for transporting nutrients and gasses throughout the body. The main component of red blood cells is hemoglobin, which is a protein that carries oxygen to the cells of the body. Hemoglobin is what gives red blood cells their color. When hemoglobin levels are low, patients are known to be anemic, which leaves them feeling sluggish and sometimes dizzy.


Finally, the last of the solid materials of blood are called platelets. Platelets are very important to the blood clotting process. When the chemicals in the blood’s plasma start to collect, they can trap platelets together and form a clot. This is why patients get scabs when they cut or scratch themselves. Platelets are actually fragments of large cells called megakaryocytes that can be found in the bone marrow and occasionally floating around the body’s blood vessels.

Blood cells make up 45% of the total volume of blood. In terms of numbers, red blood cells are the most numerous followed by platelets, and then white blood cells. The heart pumps blood throughout the body to provide nutrients and sustain life. Without blood providing our body with the tools that it needs to function, survival wouldn’t be possible.


Abrams, Peter. Physiology, All you need to know about how your body works. Bright Star Publishing, 2007.

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