It is important to understand that the hair and scalp are part of an interrelated system.
Although the hair anatomy may seem simple, it is an extremely complex system with two major structures. The hair follicle and the hair shaft. The hair follicle, which lies underneath the skin, is the living portion of the hair. The follicle contains cells and connective tissue that make up the funnel-like structure. They influence the appearance including curl pattern and color of the hair. The shaft, which lies above the surface of the skin (the hair we see), is the dead portion of the hair. It is made up of a protein called keratin that consists of 3 layers; innermost, middle and outermost layer.
The scalp consists of the epidermis and dermis. The dermis contains the hair follicles, glands, connective tissue, nerves, etc. The relationship of the hair and scalp are vital during all stages of hair growth. The hair utilizes blood vessels to feed the root, then as the hair is passing through the skin, it contacts the oil glands. The glands are significant to healthy looking hair as it diffuses vital oils that leave the hair dry and brittle or excessive and greasy.