Who knew that something that sits on the top of our head could be one of the most amazing pieces of biological engineering. Hair can be twisted, tied, and formed into almost any shape imaginable, and it is incredibly strong. Here are some amazing facts about a little thing we take for granted and are bummed about when it’s gone.
Hair can be quite a heavyweight. A single strand of hair is strong enough to hold around 3 ounces. Since there are up to 150,000 hairs on the human head, the combined hair could hold upwards of 12 tons of weight. That’s about the weight of two African elephants.
The strength comes from how a single strand of hair is arranged. Think of a cable holding up a suspension bridge. There isn’t only one cable holding the bridge. The cable is actually made up of smaller wires bundled together. Hair is arranged in much the same way.
The protein keratin is the principal component of hair. If you were to cut a hair in half at a microscopic level, you would see the cortical cells of the hair arranged in bundles, and if you looked farther in, you would see that each of these bundles have many keratin macrofibrils. This is also where you would see the melanin granules or the things that give color to hair.
If you go even further, you would see that those macrofibrils are composed of even smaller strands called microfibrils. But it doesn’t even stop there. The microfibrils are made up of protofibrils, which are four keratin strands twisted together in a helix formation.
This tiny microscopic formation is what allows the shape of a hair to change and allows it to keep its shape. The figure below shows how a strand of hair is arranged.
The color of hair is determined by the pigment melanin, which is the same thing that colors your skin. Melanin causes the skin to darken to protect it from UV rays during sun exposure. Hair, however, turns lighter in color.
The sun destroys melanin, and since skin is alive, it can respond to the damage from the sun by producing more melanin, making your skin darker. Hair, on the other hand, can’t replace the melanin since it is dead, so the hair naturally gets lighter due to the lack of pigment.
Melanin for hair color is produced at the base of the hair follicle, and there are two types; eumelanin and pheomelanin. Pheomelanin is yellow to red in color, and eumelanin is brown-red to black. These pigments ultimately determine hair color.
The reason hair turns gray, however, is simple, but the mechanism why it does is still not understood. When there is no pigment coloring the hair, it is in its natural color, white, but it is still mixed with some of the colored pigment, which makes it appear gray. There is no longer enough melanin being produced to keep the hair colored.
Why melanin is no longer produced with aging remains somewhat of a mystery, even though there are theories on what may be happening. Hair whitening, by the way, is called canities, and graying more quickly has been attributed to stress in some cases, but there is no evidence yet that stress accelerates the graying of hair.
The human head loses approximately 50–100 hairs every day after about four years of life of the hair, and men start to lose their hair around the age of 30. The discovery for the reason for natural balding, or androgenic alopecia, came from an unlikely and rather gruesome source.
In the Middle Ages and even later, some choir boys in this time were castrated so their voices wouldn’t change with puberty. What was found was that as these boys aged, they didn’t go bald. So it was discovered that sex hormones had something to play in men losing their hair with age.
Balding takes place because testosterone in men is converted to dihydrotestosterone by an enzyme. Dihydrotestosterone actually makes hair thinner and shorter, and the amount of the enzyme that converts testosterone to dihydrotestosterone is largely due to heredity.
A balding man can have normal amounts of testosterone, but with more of this enzyme, the more balding occurs. The enzyme actually doesn’t increase with age, and it’s not known whether it comes more from the mother or the father. Either way, if you’re born with more of this enzyme, there’s a good chance you’ll begin balding.
This particular enzyme isn’t the only determining factor. The number of receptors a man has for the enzyme also plays a role. The more they have of these, the more hair they will lose over time. Asian men experience hair loss at less of a rate because it’s believed they naturally have less of this enzyme in their hair follicles or a fewer amount of receptors. Unfortunately, you have no control over what you get when you are born.