NewThe Purist Q is open. Ten questions on the anatomy of skin, free.Try it
AnatomyM8
The Purist QNew

Series 1: The Skin · Episode 6, not yet released

Skin Appendages

The Anatomy Your Patient Asks About

18 minutes. 14 references, each checked at source.

Follow the podcast
Listen on SpotifyListen on Apple Podcasts

Hidradenitis suppurativa is not a disease of apocrine glands. It is a disease of follicular occlusion that happens to live in apocrine-bearing skin, and that one correction changes what you cut and when.

Episode 6 of The Anatomy Purist, Series 1: The Skin. Dev opens with a crushed thumbnail and a twenty-minute decision, then works through the appendages: the hair follicle as an epithelial reservoir, and the bulge, where that reservoir actually lives and why it does not care what phase the hair cycle is in. Eccrine versus apocrine, including the cholinergic exception and the adrenergic rule that makes it examinable. The corrected hidradenitis pathophysiology, and why "wide excision is the only strategy with evidence" is no longer a defensible sentence. Sebaceous glands, Muir-Torre, and the surveillance list most candidates truncate. And the nail complex: the two matrix zones in the correct orientation, and the paronychium/perionychium distinction almost everyone inverts.

Tiered Foundation to Purist. Every reference verified.

Themes from this episode

Practice what you just heard

Two questions on the themes of this episode, free, marked as you go. Then one from the Vault on the same ground.

Question 1 · Applied

Why do split-thickness donor sites in hair-bearing skin re-epithelialise faster?

Answer to see the explanation and the source.

Question 2 · Foundation

Sebaceous glands secrete by which mechanism?

Answer to see the explanation and the source.

From the Vault, on the same theme

Purist Finale: Comparative Anatomy & the Body’s Leftovers · Purist Locked

Waiting in a cold anaesthetic room, a frightened patient develops goosebumps, and the anaesthetist remarks that fear and cold are producing the same skin change. In a furred mammal, what did this shared machinery accomplish?

  • ARaising the coat both traps insulating air and enlarges the outline shown to a rival
  • BErect hairs channel sweat off the skin while signalling submission to dominants
  • CFollicular contraction expresses sebum, waterproofing the pelt before immersion
  • DLifting the coat vents the heat of shivering, and in fright it sheds warmth before flight
  • ETightening the dermis limits bleeding from bites while stiffening the skin as armour

Unlock to see the answer

Unlock the Vault, £49
Try ten free questions from the seriesWhat the Vault is

References

  1. Standring S, editor. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. London: Elsevier; 2020. [Textbook, no PMID.]
  2. Paus R, Cotsarelis G. The biology of hair follicles. N Engl J Med. 1999;341(7):491-7. PMID: 10441606. doi:10.1056/NEJM199908123410706
  3. Cotsarelis G, Sun TT, Lavker RM. Label-retaining cells reside in the bulge area of pilosebaceous unit: implications for follicular stem cells, hair cycle, and skin carcinogenesis. Cell. 1990;61(7):1329-37. PMID: 2364430. doi:10.1016/0092-8674(90)90696-c
  4. Ito M, Liu Y, Yang Z, et al. Stem cells in the hair follicle bulge contribute to wound repair but not to homeostasis of the epidermis. Nat Med. 2005;11(12):1351-4. PMID: 16288281. doi:10.1038/nm1328
  5. Anatomy, Skin Sweat Glands. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf ID: NBK482278.
  6. Jemec GBE. Clinical practice. Hidradenitis suppurativa. N Engl J Med. 2012;366(2):158-64. PMID: 22236226. doi:10.1056/NEJMcp1014163
  7. Sabat R, Jemec GBE, Matusiak Ł, Kimball AB, Prens E, Wolk K. Hidradenitis suppurativa. Nat Rev Dis Primers. 2020;6(1):18. PMID: 32165620. doi:10.1038/s41572-020-0149-1
  8. Zouboulis CC, Bechara FG, Benhadou F, et al. European S2k guidelines for hidradenitis suppurativa/acne inversa part 2: treatment. J Eur Acad Dermatol Venereol. 2025;39(5):899-941. Epub 2024 Dec 19. PMID: 39699926. doi:10.1111/jdv.20472
  9. Kimball AB, Okun MM, Williams DA, et al. Two phase 3 trials of adalimumab for hidradenitis suppurativa. N Engl J Med. 2016;375(5):422-34. PMID: 27518661. doi:10.1056/NEJMoa1504370
  10. Ponti G, Ponz de Leon M. Muir-Torre syndrome. Lancet Oncol. 2005;6(12):980-7. PMID: 16321766. doi:10.1016/S1470-2045(05)70465-4
  11. Muir-Torre Syndrome. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf ID: NBK513271.
  12. de Berker D. Nail anatomy. Clin Dermatol. 2013;31(5):509-15. PMID: 24079579. doi:10.1016/j.clindermatol.2013.06.006
  13. Anatomy, Skin, Nails. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf ID: NBK534769.
  14. Park DH, Singh D. The management of ingrowing toenails. BMJ. 2012;344:e2089. PMID: 22491483. doi:10.1136/bmj.e2089
Episode 5: InnervationEpisode 7: Regional Variation
All episodes

Before you go

Tell us how this one landed

What worked, what you had to replay, and what you would like covered next. Requests are the main way the running order gets decided.

Send feedbackReport an error in this episode