Overview
This lecture covers the structure and function of hair anatomy, detailing the components of hair follicles, hair growth cycles, and factors affecting hair characteristics and color.
Hair Follicle Structure
- The lower segment of the hair follicle extends from the follicle base to where the arrector pili muscle attaches.
- The bulge area of the hair follicle serves as a storage for stem cells.
- The dermal papilla supplies nourishment to the hair bulb.
Hair Growth and Development
- The arrector pili muscle causes hair to stand upright, resulting in "goosebumps."
- The active growing stage of hair is called the anagen phase.
- The shape of the hair strand (straight, wavy, curly) is determined by the shape of the hair follicle.
Hair Color and Types
- Melanin, located in the cortex of the hair, gives hair its natural color.
- Pheomelanin pigment creates yellow to red hair tones and if concentrated near the cuticle layer, the hair appears more reddish.
- The term "lanugo" describes the fine, silky hair on the body at birth.
Hair Growth Cycle
- The telogen stage is the resting phase of hair growth; the exception is it is not the growing or transitional stage.
Key Terms & Definitions
- Hair follicle — a tube-like structure in the skin from which hair grows.
- Bulge area — part of the hair follicle holding stem cells for hair growth.
- Arrector pili muscle — tiny muscle attached to the hair follicle, causing hair to stand up.
- Dermal papilla — structure at the base of the follicle that provides nutrients to growing hair.
- Anagen phase — active growth period of hair.
- Telogen stage — resting phase when hair is not growing.
- Melanin — pigment giving hair its natural color.
- Pheomelanin — type of melanin creating yellow-red tones.
- Lanugo — fine hair present at birth.
Action Items / Next Steps
- Review the hair growth cycle and key hair anatomy terms.
- Complete any assigned homework or quiz on hair structure and function.