Life is Healing


When I get a cut how does my body heal itself?

Your body is made up of trillions of cells.  It has about two hundred different types which come together to form all of your tissues and organs.  But your cells are made up of mostly water so they need more solid molecules surrounding them to provide structural support. This is provided for by the extracellular matrix which consists of gel-like molecules and fibrous proteins made by the fibroblasts. This is the connective tissue that fills up the spaces between the cells with mainly collagen (and other molecules) that provide physical support so your cells can stay in place and do what they’re supposed to do.  It’s important to note here that the biomechanical qualities (e.g. tensile strength, compressibility and elasticity), of the extracellular matrix can vary significantly from one organ to another (e.g. lungs vs skin vs bone).  When you cut yourself, not only does your body have to know how to stop the bleeding but also how to repair and replace the damaged blood vessels and the surrounding connective and functional tissue.  It does this in four phases. 

When you get cut, this exposes blood to the collagen in the connective tissue that sits below the lining of the blood vessel (endothelium) in your skin.  This triggers clotting (first phase) which involves three almost simultaneous actions.  First, the muscle around the blood vessel contracts to close down the opening and prevent further blood loss. Second, the platelets in the blood become activated and start sticking to each other and the wound and attract others to pile on to form a platelet plug.  Third, the clotting factors in the blood undergo the coagulation cascade (a series of chemical reactions) to form a firm fibrin clot at the site of injury.

Over the first five to ten minutes, as clotting comes to an end, a build-up of chemicals released by platelets and injured cells causes the blood vessels to go from being contracted to being more relaxed.   Over the next thirty to sixty minutes this brings more blood to the site of injury and is the beginning of inflammation (second phase).  During this phase (which lasts about a week) immune cells (attracted by released chemicals) clean up the site by killing bacteria and digesting damaged connective tissue and cells. 

Within a few days, as the immune cells do their job they send out chemicals that attract cells that line the blood vessels (endothelial cells).  The low level of oxygen in the wound stimulates them to start making new blood vessels as proliferation (third phase) gets under way.  The immune cells also release other chemicals that attract fibroblasts which move in and deposit collagen and other structural support molecules that make up the extracellular matrix.  All of this takes place below the clot that temporarily keeps the tissues together during the healing process.  The fibroblasts then send out chemicals to attract the cells that will become the new skin (epithelium) and with the help of the newly laid down extracellular matrix these cells come to the surface while dissolving the clot along the way. 

As the proliferation phase ends and the scab is removed the skin only has about half of its normal resistance strength.  This is when maturation and remodeling (fourth phase) begins and can last for several months.  During this phase the collagen in the connective tissue will be replaced and strengthened so that the skin will eventually look and function normally. 

Three Questions for Darwin

    1. Where did the information come from to tell my body how to make the extracellular matrix that matches the biomechanical needs of its different organs?

    2. Where did the information come from that taught my body how to perform the four processes needed to heal itself after being cut?

    3. If so many different cells and molecules, acting as chemical messengers, are needed just to heal a small cut then how could such a system have come into being within a viable organism based on your theory?  

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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