A long, long time ago. In a land far, far away I did an article with Dr. Leonard Sperling on hair anatomy. This came after publishing our articles on the Ridgeback Anomaly and another article on scalp whorls. Please refer to my CV for more details. I came across these slides and thought it might be good to get these drawings out there again. I have no idea where the originals are and in those days we did not have computers that could handle these kinds of images so I did them by hand using drawing pens and colored sticky sheets that I would cut with an X-Aacto knife. The arrows were also rubbed on…
HAIR CYCLE: This image demonstrates the natural hair cycle.
- Anagen Phase–This is the growth phase and varies from individual to individual. What determines how long your hair grows depends on how long your anagen cycle is and can be as long as 7 years.
- Catagen Phase–This is a transitional phase and lasts for about 10 days.
- Telogen Phase–This phase produces a “club” hair that falls out. The follicle may lay dormant for up to 3 months before growing again from the secondary germ.
These three drawings show the anatomical detail of the hair follicle in the various stages. There are text books written just on hair disease and the list is large, ranging from Alopecia Areata to genetic disorders, such as Menke’s and Pili Torti. There are conditions related to hair trauma such as traction alopecia and trichorrhexis nodosa. Microscopic evaluations can be very helpful. The trick is identifying the anatomy under the microscope…
The figure above demonstrates some of the anatomy as observed under the microscope.
A. Medulla
B. Cortex
C. Inner root sheath
D. Outer root sheath
E. Isthmus
F. Sebaceous Gland
G. Infundibulum
This drawing demonstrates the continuum of the skin with the hair follicle lining…this also applies to the gastrointestinal tract. The actual hair structure is an external creation of the skin…in this regard the actual hair is a slow moving bullet loaded into the follicular shaft ready for discharge. The hair is launched when it cycles into the Catagen phase and the trigger is the Telogen phase…minimal traction of the hair strand at this point launches it into the world…free at last. So, hair is essentially foreign material and when the follicular lining is violated, exposing the hair structure to deeper tissues the body responds to it much like an infection…resulting in inflammation and scarring. This is what happens in disorders such as Acne Keloidalis Nuchae and Pseudofolliculitis Barbae. To read more about hair anatomy and cycles click HERE.