Answer:
Anagen Growth stage of hair follicle cycle
Catagen Regression and involution stage of hair follicle cycle
Telogen Resting stage of hair follicle cycle
Exogen Active hair shaft shedding stage of hair follicle cycle
Kenogen Telogen follicle without club hair form
Club hair Fully keratinized, dead hair formed at telogen stage
Lanugo hair Fine hairs on the fetus body; shed in utero or within the first weeks after birth
Vellus hair Non-pigmented, and generally non-medullated; short hairs
Terminal hairs Large and pigmented hairs
Hair matrix Consists of rapidly proliferating keratinocytes that move upwards to produce the hair shaft
Follicular dermal papilla (DP) Onion-shaped portion of hair bulb surrounded by hair matrix cells, consists of mesenchymally derived tissues
Hair bulb Lowermost portion of the hair follicle, includes the follicular dermal papilla and the hair matrix
Isthmus The lower portion of the upper part of hair follicle between the opening of the sebaceous gland and the insertion of arrector pili muscle
Infundibulum Uppermost portion of the hair follicle extending from the opening of the sebaceous gland to the surface of the skin
Bulge Segment of the outer root sheath located at insertion of arrector pili muscle
Inner root sheath (IRS) Guides the hair shaft and helps to take a shape; coats the hair shaft up to the isthmus level
Outer root sheath (ORS) Extends along from the hair bulb to the infundibulum and epidermis serves as a reservoir of stem cells
Connective tissue sheath (CTS) Significant mesenchymal follicular layer that adheres to the basement membrane of the hair follicle and interacts with the follicular dermal papilla
