Telogen phase of hair growth lasts for ?
First, I need to recall the hair growth cycle phases. Hair goes through anagen (growth phase), catagen (transitional), and telogen (resting phase). The telogen phase is when the hair follicle is at rest, and the old hair is shed once the new hair starts growing. How long does telogen last? I remember that the telogen phase is the shortest phase, but wait, no—actually, the anagen phase is the longest, varying by hair type. For scalp hair, anagen is about 2-7 years, catagen is 2-3 weeks, and telogen is around 3 months. So the correct answer here would be 3 months.
The core concept here is the hair growth cycle and the duration of each phase. The question is testing knowledge of the telogen phase's duration. The key is that telogen is the resting phase and lasts the longest among the three phases? Wait, no. Wait, anagen is the longest, then telogen is next? Let me double-check. Anagen is the growth phase, which is the longest. Catagen is the shortest, a few weeks. Telogen is the resting phase, lasting about 3 months. After telogen, the hair is shed, and a new anagen phase begins. So the telogen phase is about 3 months. That makes sense because if each hair spends a significant time in telogen, it explains why hair loss can happen in cycles. For example, conditions like telogen effluvium cause a large number of hairs to enter telogen prematurely, leading to increased shedding after the 3-month period.
Now, the user's correct answer is option C, which is 3 months. The other options would be incorrect durations. For example, if the options were A. 2 weeks, B. 1 month, C. 3 months, D. 6 months, then A and B would be too short (catagen is 2-3 weeks), D would be longer than telogen. So the correct answer is C.
The clinical pearl here is that understanding the hair cycle phases helps in diagnosing hair loss conditions. Telogen effluvium is a common cause of diffuse hair loss, and knowing the telogen duration helps in timing the onset of symptoms after a precipitating event like stress or illness.
**Core Concept**
The hair growth cycle consists of three phases: anagen (growth), catagen (regression), and telogen (resting). The telogen phase is critical for follicle quiescence before re-entering anagen. Its duration is a key clinical factor in conditions like telogen effluvium.
**Why the Correct Answer is Right**
The telogen phase lasts approximately **3 months** for scalp hair. During this time, the follicle is inactive, and the hair shaft remains in the follicle until it is shed. This phase accounts for ~10-15% of scalp hairs at any time.