Ziering Medical Glossary

Club Hair An otherwise normal and fully developed hair strand that has stopped growing. It is named for the bulbous or club-like appearance of keratin which accumulates at the end of the hair.

Companion Layer A single layer of flattened cells derived from the hair matrix and situated between the outer root sheath (ORS) and the inner root sheath (IRS) of the hair follicle. The companion layer acts a slippage plane allowing for key movement to occur between adjacent structures, and additionally is felt to function in both a communicative and nutritive role in a hair’s metabolism.

Crown Area The area in the rearward top portion of the head. This area commonly contains some hair which grows in a radiating fashion from its center point and is referred to as a whorl or whirl. The crown region is often involved in male pattern hair loss.

Densitometry Densitometry is a measurement technique employing a device designed to both magnify the area of observation as well as measure it’s size for the purpose of generating an understanding of the density or concentration of hair within the area as well as understanding follicular unit composition and degree of miniaturization. With serial examinations this tool can be used to assess the efficacy of therapy to safeguard hair.

Density A number used in hair transplant surgery and hair loss treatment defined as the concentration of hair within a specified area [ typically a cm squared ]. Different ethnicities have characteristically different hair densities as well as follicular unit composition.

Dermal Papilla The dermal papilla is situated at the base of the hair follicle. The dermal papilla contains nerves and blood vessels, which supply glucose for energy and amino acids to make keratin. This structure is extremely important in the regulation of hair growth since it has receptors for both androgens and hair-promoting agents.