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The largest organ in the human body: Is it really the skin?

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There are many allusions to the skin as the largest organ in the human body.  But there are two key contradictions of this claim. The first is the vascular endothelium.  The second is the largest organ in the human bodydimensions of size.

The skin is the three layers of protective covering of the body.  The outermost layer is the epidermis.  The middle layer is the dermis and the deepest or bottom layer is the hypodermis, which is composed of connective tissue and fat.

The surface area of the skin depends on several factors including the size of a person.  But on the average it covers between 1.5 to 2 square meters.  This is equivalent to between 16 to 21.53 square feet. That’s close to the size of a twin bed mattress which is 19.48 square feet. The table below explains.

largest organ in the human bodyThe skin accounts for approximately 16% of one’s body weight.  That amounts to 20 or more pounds in most adults. Skin thickness depends upon a number of factors.  They include age, gender, body area and race.  But in general it can range from between 1.5 mm and 2.54 mm.

The surface area of the vascular endothelium (VE) ranges between 4000 and 7000 square meters.  That’s about the size of a football field. Table 2 below and the following paragraph clarify the point.

largest organ in the human bodyThe square footage of a football field is length x width. NFL, college and high school football fields are 360 feet long and 160 feet wide, not counting the end zones. Calculation of the square footage is:
360 ft. x 160 ft. = 57,600 ft2

The thickness of the vascular endothelium ranges from 1 to 3 µm.  A µm is one thousandth of a millimeter or 1 mm x 10-3.   It weighs about 1 kilogram which is 2.204633 pounds. That is roughly 1% of a person’s body weight.

In comparing the size of the skin with the endothelium, cubic feet or volume might be a tad more accurate because it is a three-dimensional measurement.  But square surface area yields the best contrast. 

The volume or dimensions in cubic feet (ft3) is the square area multiplied by the depth or thickness of either structure. Since the thickness is very small relative to the square area the skin advantage is not going to change the comparison that much. 

The skin is one thousand times thicker than the endothelium. Table 3 below elucidates that fact.

largest organ in the human bodyThe vascular endothelium is also much larger than the skin in terms of its volume, even though it is thinner.  Table 4 that follows expounds the point.

largest organ in the human bodyIf the math is annoying just remember, the skin is about a thousand times thicker than the endothelium. Imagine a 1000-inch deep rectangular pool the size of a twin bed mattress. That depth is equivalent to 83.33 feet.  Then imagine a 1- inch deep rectangular pool the size of a football field. Which one would hold the most water?  Review table 4 above.

Many of the sources that repute the skin as being the largest organ in the human body refer to its weight in the same context. The reason perhaps is that all of the formulas for calculating skin surface area use weight as one of the input variables.  But weight is not really a dimension of size.

The weight and size of various objects often correlate, but such is not always the case.  There are two reasons why.  They are the principles of molecular mass and density.  An example is a beach ball inflated to twice the diameter of a bowling ball.  The bowling ball weighs more because it is composed of heavier molecules that are more compressed. But the beach ball is bigger.

In fairness to those who have dubbed the skin as the largest organ in the human body, it is, with a change of prepositions and with one stipulation.  Because of its many nerve endings and the role it plays in sensation, it is the largest sensory organ of the body.   It is not the largest organ in the human body in general. But it is the heaviest. 

If there is any doubt that the skin is not the largest organ in the human body or of the body, just do the math.  

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