Blood is Life



Why is our blood red?

Just like any working machine, the laws of nature demand that for your body to do the things it needs to do to survive it must have enough energy.  As previous articles have explained, to have enough energy your cells must have enough oxygen.  Oxygen makes up one-fifth of the air and your body gets it by breathing it into your lungs where it travels down the airways to the alveoli and enters the blood.  But, getting oxygen from outside your body into your blood only solves half of the problem.  Just as an oxygen company must figure out a way to get its product to its customers, so too, the body must figure out a way to get the oxygen it brings in through its lungs to its trillions of cells.  However, when it comes to transporting oxygen in your blood, your body faces a dilemma.  Blood is made up of cells that float in water and this water has many chemicals (like salt and glucose) dissolved within it.  Unfortunately, oxygen does not dissolve well in water, in fact if it was the only way you had to transport oxygen you could not survive for even a few seconds.  So what’s a body to do? 

The solution to this dilemma is a complex molecule called hemoglobin.  Hemoglobin is made in the red blood cells that, with others (white blood cells and platelets), float within your blood.  Hemoglobin contains iron (Fe) to which oxygen can easily bind and so be transported within your blood.  When the iron in your hemoglobin is fully loaded with oxygen its color is red and this is why arterial blood is red.  After it gives up some of its oxygen to the tissues and returns to the heart (through the veins) hemoglobin takes on a bluish hue.  Look at the blood vessels on the back of your hands.  Do you think they are arteries or veins?

But we’re not finished yet.  For your blood to transport enough oxygen to meet your body’s energy needs, it has to have enough red blood cells with enough hemoglobin.  There are certain cells in the kidney that are thought to detect the oxygen content of the blood and in response send out a hormone called erythropoietin.  Erythropoietin goes to your bone marrow and by attaching, (like a key in a lock) to specific receptors on the surface of certain immature (stem) cells, orders them to become red blood cells capable of making hemoglobin.  Red blood cells tend to live for only 120 days, so to make sure your blood has enough your bone marrow must keep making them at a rate of about two to three million every second and that’s why your blood is red.

Three Questions for Mr. Darwin

  1. Where did the information come from to tell my body how to make red blood cells and how do they know how to take in and use iron to make hemoglobin?

  2. Where did the information come from to tell my specialized kidney cells how to make erythropoietin while at the same time producing the specific receptors on the surface of the bone marrow stem cells?

  3. Where is the information in the body that tells the specialized kidney cells how much erythropoietin they need to send out to make sure my body has enough red blood cells and hemoglobin so it can transport enough oxygen to my tissues and organs?


Also see Dr. Glicksman's Series on

"Beyond Irreducible Complexity"

"Exercise Your Wonder"


Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.

Comments and questions are welcome.

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