In order to understand male pattern baldness, it is first necessary to look at the first origins of hair and the necessity of the hair follicle. While at first glance it may seem that hair is a rather uncomplicated structure, this is untrue.
Hair: The Origins
The hair follicles of a developing fetus are accomplished within the first six months. Humans are born with an estimated five million hair follicles on the body. Approximately one million of these hair follicles is located on the head, with about one hundred thousand located to the scalp.
It is important to note that the number of hair follicles an individual is born with, is the most hair follicles that individual will ever have. It is not possible to naturally generate new hair follicles. Therefore, individuals will have a decrease in the overall density of hair over time, as the body continues to develop and grow. Hair is divided into two structures with distinct characteristics. These two structures are the hair follicle and the hair shaft.
The Hair Follicle
The hair follicle is located within the skin. It has a tunnel shaped appearance that extends through the skin layers, both the epidermis and dermis. The hair follicle itself has several layers. Each layer is responsible for the completion of specific functions. The papilla is located at the bottom of the hair follicle. It contains tiny blood vessels known as capillaries, responsible for the delivery of blood and nourishments to the cells of the hair follicle.
The bottom part of the hair follicle, surrounding the papilla, is known as the bulb. The bulb is the living part of the hair and is capable of dividing every 24 hours. That rate of division is markedly higher than other cells in the body.
The follicle itself is surrounded by two sheaths that are responsible for the protection of the growing hair shaft. These sheaths are accompanied by the presence of certain glands, particularly an oil (sebaceous) gland and a scent (apocrine) gland.
The Hair Shaft
The shaft of the hair is visible from above the scalp. It is composed of a protein known as keratin. Keratin is particularly hard and is dead. Hair is not a living structure of the human body. Typically, hair grows at a rate of approximately 0.35 millimeters per day, for a total length of approximately 6 inches per year. However, human hair growth is dependent upon various factors, both environmental and genetic.
Male Pattern Baldness
Male pattern baldness is associated with a gradual shrinking of the hair follicle. As the hair follicle decreases in size, it becomes increasingly harder for the shaft to grow. Eventually, the hair follicle will decrease in size and hair will fall out and not be re-grown.
Male pattern baldness is a genetically inherited condition. Certain males are born with sensitivity to a specific enzyme known as DHT (dihydrotestosterone). Over time, DHT is cause for the shrinking of hair follicles.
Typically, male pattern baldness is limited to specific areas, particularly the mid anterior scalp and temples. It is thought that these areas of the body are more sensitive to the presence of DHT.
Sources:
http://www.webmd.com/skin-problems-and-treatments/hair-loss/science-hair
http://www.webmd.com/skin-problems-and-treatments/hair-loss/hair-loss-causes
