The Cardiovascular System - Your Blood

Publication Date: 
Thu, 10/01/2015
By: Alere Staff

  At times, simply the sight of blood can make a person squeamish and pale. However, that liquid that can make a person weak is one of the largest organs that circulates through the body and keeps you strong. Blood is a specialized body fluid that performs many functions including the transportation of oxygen and nutrients to body tissues, carrying cells and antibodies to fight various infections, removing waste products, regulating your body’s temperature and forming blood clots to minimize loss when trauma occurs.1 As a patient on warfarin, you are likely already aware of the clotting function of blood.

Blood Components  

There is a lot more to your blood than you might think. While physically appearing red in color, it is actually made of four main components: fluid called plasma, a yellowish mixture of water, sugar, fat, protein and salts, red blood cells, white blood cells and platelets.2 Blood also contains other various nutrients, waste products, clotting proteins and hormones. The red color marks the appearance because red blood cells, well known for their bright red color, are the most abundant cell, making up almost 40-45% of blood’s total volume.1

Red blood cells contain a special red-colored protein called hemoglobin that aids in the transport of oxygen throughout the body as well as carrying carbon dioxide, a waste product, back to the lungs to be exhaled. Unlike other body cells, a red blood cell does not contain a nucleus, making it easy for it to change shape and fit through the various sizes of blood vessels in your body. This advantage, however, has a drawback: all this shape-shifting and travel takes its toll on the cell making the average life-span of a red blood cell short, surviving on average only 120 days.1

The blood that runs through the blood vessels of the body is considered “whole blood”, containing 55% plasma and 45% percent blood cells. On average, about seven to eight percent of your total body weight is your whole blood. An average-sized man has about twelve pints of blood within their body while an average-sized woman will have about nine pints.1

All cells are produced within your bone marrow, whether red blood cells or platelets. Flat bones including your skull or pelvis are the primary bones where blood cells are made.2 All blood cells start as “master cells” called stem cells, most well-known for being found in the umbilical cords of newborn babies. These stem cells, though, are found throughout blood and bone marrow of people of all ages.1,2 Stem cells will eventually become whatever kind of blood cell the body needs at that time, whether a clot needs to form or an infection needs to be fought.

Blood Types and Tests

In 1901, physician Karl Landsteiner found that blood actually had types, with the differences in the types based on the specific proteins found on the surface of the red cells and antibodies found within the plasma. The four main types of blood found included Type A, Type B, Type AB and Type O.2 Blood can be transfused from one person to another who needs it, as long as the particular blood types are well-matched. Once collected from healthy donors, blood is tested for any presence of disease as well as separated between its main parts. Thus if a patient needs just plasma or red cells, they receive these cells. With a donation of blood, you can help more than one person.2

As you can see, blood is an important factor of the human body’s circulatory system. When something is wrong with your blood, it can affect more than just the blood itself but other organs and tissue. A complete blood count, or CBC, is a test given by your doctor that relays to them important information about your blood, including type and the number of cells within the fluid including red blood percentage and protein content. Tests like these help your doctor to determine whether or not you have condition like anemia or other infections. So, while looking at your blood may make you weak in the knees, just close your eyes and remember how blood brings life and helps you to stay healthy.

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  1. American Society of Hematology. Blood Basics. 2015. Retrieved August 27, 2015 from website:
  2. Bloodworks Northwest. Introduction to Hematology. 2015. Retrieved August 28, 2015 from website: