Hair Cycle and Hair Disorders: Introduction

00:01 Welcome to our lecture on common hair disorders in skin of color.

00:06 Now let's look at the normal scalp hair growth patterns.

00:10 The average hair growth rate is about 0.35mm per day.

00:16 This rate is lower in the elderly and patients with chronic illnesses.

00:22 So the hair cycle has got three phases.

00:25 The anagen phase, catagen phase, and telogen.

00:30 The growth phase lasts about 2 to 6 years and this is the actively growing follicle.

00:38 The catagen phase is a follicular regression stage or transitional stage of the hair follicle. The telogen or resting phase lasts about 2 to 3 months.

00:50 So each hair follicle goes through its own its own hair cycle.

00:58 80% of hair follicles are in active growing phase, which is the anagen. 10 to 20% are in the resting phase or telogen.

01:10 The telogen hair fibers are responsible for daily hair shed, and the average daily hair loss is about 25 to 100 hair fibers per day, depending on the ethnicity of the individual.

01:26 On the screen, you can see the various anatomical parts of the scalp, and on this table you see the differences between Afro -textured hair, Caucasian hair, and Asian hair.

01:40 And this is depicting the number of follicles and the number of hairs per square millimeter. So what is alopecia or hair loss? Alopecia is a broad term referring to hair loss in an area where it is expected to be present. And alopecia can be classified into localized or diffuse.

02:08 It can be temporary or permanent, and it may be scarring or non-scarring and usually affect both sexes and all age groups.

02:19 So how do we classify alopecia? We classify alopecia in various ways.

02:27 Non-scarring and scarring alopecia.

02:32 Non-scarring means if one loses her, it may grow again.

02:38 However, scarring alopecia refers to hair loss, where you've lost the hair follicle and the hair will not grow again.

02:48 It is important for the scarring alopecia to ensure that we approach it as a psychological emergency, because once you lose the hair follicle, it's very difficult to get it back.

03:03 We can also classify alopecia according to the histological cells that we see in lymphocytic neutrophilic, or mixed.