From Ohr Avigdor Shaar Bechina by Rabbi Avigdor Miller
The hair, like everything else in the body, is a multitude of wonderful arrangements. Each hair has its own root, which is surrounded by a receptacle of oil. That little pool of oil keeps the hair supple.
And hair is not just a simple thing. Under the microscope or even a magnifying glass, hair can be seen as a tower, with successive stories, each of which is a little thinner than the one below it. Each story grows out from the one below it, with the start of each stage being clearly visible.
Hair is not just a simple thing
Now the hair of course protects the body and the head. The Chovos Halevavos cites this as an example how Hashem has provided means to protect the delicate organs of the body. It is noteworthy that women have hair on their heads all their lives whereas many men don’t. Hair provides an extra measure of protection for women, who are less able to defend themselves when attacked. Also, younger men, who are more likely to go into battle, have an extra need for protection and so they generally don’t lose their hair until they get older.
But in addition to protection, hair serves other purposes such as promoting marriage and procreation. A young man with a head of healthy hair is like an advertisement that he is capable of having children. A woman’s hair makes her attractive and serves to announce that she is ready to get married. It is amazing to see somebody with long hair and to realize that all of this profusion of material was produced by the skin. A person doesn’t eat hair, but the food he eats turns into hair, a miraculous conversion which is achieved by the cells in the skin of the head.