One Opinion About The Duration Of The Catagen Phase
The catagen phase begins when there are no longer mitotic cells in the matrix. It ends with the loss of the sheaths, when the bulb reaches the infundibulum.
There is some disagreement about how long the catagen phase lasts. Perhaps anatomy and histology can provide us with an answer.
Let us observe this follicle and this hair closely. It is the beginning of the catagen phase. It would be easy to mistake the hair for one in the anagen phase. The sheaths are still intact and their colouring is obtained from cinnamaldehydes, which cleaves to the citrulline of the inner epithelial sheath. The bulb is detached from the papilla and the matrix. The matrix is beginning to degenerate and is starting to form the sac. All these various factors indicate that the anagen phase is over. The presence of perifollicular adipose tissue shows that this bulb is still embedded to a depth of approx. 6 – 7 mm (6000 – 7000 micron). This catagen hair can no longer grow at a rate of 400 microns a day (10 mm a month), as it did before, since the matrix does not now contain any mitotic cells. The hair (together with the inner epithelial sheath to which it is attached) will have to climb back up the follicle at the same (and much less impressive speed) of ordinary skin regeneration, i.e., at a rate of approximately 65 microns a day. To reach the infundibulum, it will have to travel 6,500 microns. Since it will be moving at a speed of 65 microns per day, this will take at least 90 – 100 days. The catagen phase of this hair will last at least 3 months.
The length of the catagen phase is proportional to the depth of the follicle. It will last 2 weeks for miniaturized hair but over 3 months with deep, terminal hair.
Adachi K., Takayasu S., Takashima I., Kano M., Kondo S.: “Human hair follicles: metabolism and control mechanism” J Soc Cosmet Chem 1970; 2: 911.
Adachi K.: “The metabolism and control mechanism of human hair follicles” Curr Probl Dermatol 1873; 5: 37.
Barman J.M., Astore I., Pecoraro V.: “The normal trichogram of the adult” J. Invest. Derm 1965; 42: 421.
Bosco I.: “Dermatologia generale” Roma, SEU, 1970. 33 – 35.
Caputo R., Alessi E.: “Istologia della cute e degli annessi cutanei” in: Serri F. “Trattato di dermatologia” PICCIN, Padova, 1986,1°. 38 – 46 .
De Villez R.L.: “The growth and loss of hair”, Kalamazoo – Michigan, Upjohn Company, 1986.
Duni D., Cislaghi E.: “Elementi di tricologia” Milano, SEPeM, 1988. 59-62.
Enjolras O.: “Centomila capelli” Parigi, Parente L.,1978. l0-11.
Kligman A.M.: “The human hair cycle” J Invest Derm 1959; 33: 307.
Marliani A.: “TRICOLOGIA” -diagnostica e terapia- fascicolo 1°; Firenze, TricoItalia: 2007.
Orentreich N., Durr N.P.: “Biology of scalp hair growth” Clin Plast Surg 1982; 9: 195.
Paus R., Handjski B., Czametzki B.M., Eichmuller S.: “Biology of hair follicle” Hautarzt 1994; 45/11: 8; 8 – 825.
Rebora A.: “the trichogram” in: “Hair and Aestetic Medicine”, Salus Internazionale, Roma, 1984: 39-42.
Saitoh M., Uzuca M., Sakamoto M.: “Human hair cycle” J Invest Dermatol 1970; 65:54