Final answer:
The natural flow or wave pattern of hair is determined by the shape of the hair follicle. Circular follicles lead to straight hair, while oval or irregular ones result in wavy or curly hair. The hair grows out in the shape of the follicle, starts as stem cells inside the follicle, and the visible part outside the skin is the hair shaft.
Step-by-step explanation:
The natural flow or wave pattern of the hair is determined by the shape of the hair follicle. When the follicle is circular in shape, the hair is straight, and when the follicle is oval or irregular, the hair tends to be wavy or curly. This is because of the way the hair grows out from the hair follicle and takes on the shape of the follicle.
Hair growth begins inside the follicle, where stem cells divide and allow the hair to grow. A layer of basal cells produces the hair shaft within the follicle. The part of the hair that is visible above the skin surface, which consists of dead cells, is known as the hair shaft.