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📘 How does hair grow?

The visible hair shaft is only the part that has emerged from the skin: growth begins inside a follicle, where a bulb contains rapidly dividing matrix cells. Hair is therefore a product of a living mini-organ, not a strand that grows from i

5
lessons
~25 min
to learn
Adults
level
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What you’ll learn

  1. A follicle is a living factoryIdentify the bulb, matrix, dermal papilla, sheaths, and shaft as parts of a living hair-producing organ.Hair is built inside a follicle by coordinated dermal and epithelial cells.
  2. The cycle has three main phasesDescribe anagen, catagen, and telogen and compare their timing and activity.Follicles grow, regress, and rest in a repeating three-phase cycle.
  3. Follicles restart from a local nicheExplain how stem cells, dermal-papilla signals, and pigment cells help restart and shape growth.A local signaling niche controls activation, stopping, and pigmentation.
  4. Shedding is part of replacementConnect club hairs, asynchronous cycles, and delayed shedding to normal and increased hair loss.Shedding is compatible with healthy follicles because follicles run on different schedules.
  5. Why growth can become shorterApply the cycle to maximum length, miniaturization, shaving, and the reason hair stops growing.Hair length reflects anagen duration, while follicle changes can shorten and narrow the fiber.

Questions this course answers

Where are new hair-shaft cells added?

Matrix cells near the bulb divide and differentiate into the hair shaft.

Put the main follicle phases in order.

Follicles grow actively in anagen, regress in catagen, and rest in telogen before returning to anagen.

Why can scalp hair grow much longer than an eyelash?

Maximum length mainly reflects how long the follicle remains in active anagen at that body site.

Match each follicle feature with its role.

These parts cooperate, but they do different jobs within the follicle.

What is a telogen club hair?

A club hair is the compacted, non-growing fiber associated with telogen.

Why can normal shedding happen without overall baldness?

Staggered schedules keep the scalp from losing all its hairs at once.

Grounded in trusted sources

  • DermNet NZ, Hair shedding, https://dermnetnz.org/topics/hair-shedding
  • StatPearls, Physiology, Hair, NCBI Bookshelf, https://www.ncbi.nlm.nih.gov/books/NBK499948/
  • Plowman and Harland, The Follicle Cycle in Brief, PubMed, https://pubmed.ncbi.nlm.nih.gov/29797264/
  • Krause and Foitzik, Biology of the hair follicle: the basics, PubMed, https://pubmed.ncbi.nlm.nih.gov/16616298/
  • The Biology and Genomics of Human Hair Follicles: A Focus on Androgenetic Alopecia, PMC, https://pmc.ncbi.nlm.nih.gov/articles/PMC10932098/
  • Wikimedia Commons MediaWiki API, image metadata and thumbnails, https://commons.wikimedia.org/w/api.php

Every Wunder lesson is built from real, reputable sources — never invented.

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