sentence: Growth cycles are controlled by a chemical signal like epidermal growth factor.
sentences_before: Each phase has several morphologically and histologically distinguishable sub-phases. There is also a shedding phase, or 'exogen', that is independent of anagen and telogen in which one of several hairs that might arise from a single follicle exits. The cycle's length varies on different parts of the body.
concept_name: growth cycle
headings: Hair follicle Hair-follicle cycling
categories: Hair Integumentary system