1. THE HAIR CYCLE

2. Introduction
• Hair follicles undergo a repetitive
sequence of growth and rest known as
the hair cycle
• The timing of the phases of the hair cycle
and its overall duration varies between
body site, gender, species and races.

3. Stages of hair cycle
• ANAGEN
– Growth / Progression
• CATAGEN
– Involution / Regression
• TELOGEN
– Resting / Quiscent

4. • aa

5. •a

6. Anagen
• Duration of anagen determines the final
length of the hair
• Length varies according to body site
– Scalp hair
– Legs
– Arms
– Eyelashes
– Fingers
02-08 Y
05-07 M
02-03 M
01-06 M
01-03 M

7. Anagen
• 90 to 93 percent of scalp follicles are in
anagen at any given time. Growth rate :
01 cm / 28 days
• Anagen can be divided into seven stages:
– I : Mitotic Onset in Germ Cell Epithelium 
Dermal Papillae (DP) growth
– II : Bulb Matrix Cells envelope DP 
Differentiation  Descent of Bulb

8. Anagen
• Stage III
– Differentiation (Bulb Matrix Cells  Follicular Cells)
• Stage IV
– Matrix melanocytes reactivate
• Stage V
– Hair shaft emerges  Telopstosis
• Stage VI
– New hair shaft emerges from skin surface
• Stage VII
– Stable progressive growth

9. • aa

10. Bulge hypothesis
• Franz Von Leydig
• Lower portion of the follicle cyclically
regenerates, the upper portion stays
constant
• The hair bulge harbours stem cells which
give rise to all epithelial layers of hair follicle
during anagen
• Loss of hair follicle stem cells in bulge leads
to permanent or cicatricial alopecia

11. Catagen
• Onset is marked by cessation of mitotic
activity of matrix cells
• There is well coordinated apoptosis in
the cyclic portion of hair follicle
• Pigment production by melanocytes
ceases before matrix cell proliferation,
thus leading to the non pigmented
proximal end of telogen club hair

12. Catagen
• The lower follicle retracts upwards with
dermal papilla
• The perifollicular sheath forms a fibrous
streamer comprised of fibroblasts,small
blood vessels and collagen; Cuts off
blood supply
• 1 to 2% of follicles are in catagen
• Duration is 2-3 weeks approx

13. Telogen
• Stage of rest / QUISCENT
• Approximately 10% of scalp hair are in
Telogen
• Duration is 02-03 months
• Shedding is an active process
• Formation of Club Root - Fully
keratinized, dead hair

14. Telogen hair

15. Exogen
• Stage of active hair shedding TELOPTOSIS
• 1% of telogen hair are in exogen at a
given time

16. Kenogen
• Usually whenever a telogen hair is shed, an
anagen hair is already present in the follicle
to replace it
• At times, the follicle stays empty after
telogen sheds, this is known as kenogen
• May last from weeks to months, seen in
patients of androgenetic
alopecia, prepubertal children

17. THANK YOU