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

Series 1: The Skin · Episode 8, not yet released

The Hypodermis

The Layer That Explains Everything Else

23 minutes. 16 references, each checked at source.

Follow the podcast
Listen on SpotifyListen on Apple Podcasts

The frontal branch of the facial nerve does not cross the zygomatic arch inside the SMAS. It runs deeper, in the innominate fascia, beneath both the SMAS and the superficial temporal fascia. Agarwal and colleagues showed it in eighteen fresh cadaver hemifaces in 2010, with histology in six.

That correction cuts both ways, and Episode 8 gives you both halves. It is why the SMAS can be elevated and divided safely to the superior border of the arch. And it is why the nerve still gets injured, not because it is superficial, but because there are only a few millimetres of soft tissue covering it, and cautery over the arch transmits heat straight down.

Also in this episode: the hypodermis and its four functions, and why it is not a synonym for the superficial fascia. The facial fat compartments, and why ageing is compartmental deflation rather than simple descent. The SMAS as genuinely contested anatomy, Mitz and Peyronie described it in the parotid and cheek in 1976, and never claimed it ran across the whole face. The great auricular nerve, injured more often in facelift than all the other nerves combined, and almost never taught. Pitanguy's line, and the difference between a traje

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

What is the anatomical basis of skin necrosis following superficial liposuction?

Answer to see the explanation and the source.

Question 2 · Foundation

What is the hypodermis composed of?

Answer to see the explanation and the source.

From the Vault, on the same theme

General Principles: Fascia, Compartments & Tissue Planes · Purist Locked

In a septic patient with a small patch of dusky skin, a probe passed at operation glides for many centimetres between the subcutaneous fat and the investing fascia, through grey tissue that does not bleed, far beyond the visible change. Why does this infection advance so far along that interface while the skin above still looks viable?

  • ADense fascia shields the organisms there from circulating antibiotics
  • BBacterial toxins spare the dermal capillaries until late in the disease
  • CThe skin survives on a self-contained dermal plexus needing no perforators
  • DThe plane is loose areolar tissue with a sparse blood supply of its own
  • ELymphatic flow in the plane carries organisms ahead of the advancing margin

Unlock to see the answer

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

References

  1. Mitz V, Peyronie M. The superficial musculo-aponeurotic system (SMAS) in the parotid and cheek area. Plast Reconstr Surg. 1976;58(1):80-8. PMID: 935283. doi:10.1097/00006534-197607000-00013
  2. Stuzin JM, Baker TJ, Gordon HL. The relationship of the superficial and deep facial fascias: relevance to rhytidectomy and aging. Plast Reconstr Surg. 1992;89(3):441-9; discussion 450-1. PMID: 1741467.
  3. Rohrich RJ, Pessa JE. The fat compartments of the face: anatomy and clinical implications for cosmetic surgery. Plast Reconstr Surg. 2007;119(7):2219-27. PMID: 17519724. doi:10.1097/01.prs.0000265403.66886.54
  4. Rohrich RJ, Pessa JE, Ristow B. The youthful cheek and the deep medial fat compartment. Plast Reconstr Surg. 2008;121(6):2107-12. PMID: 18520902. doi:10.1097/PRS.0b013e31817123c6
  5. Agarwal CA, Mendenhall SD, Foreman KB, Owsley JQ. The course of the frontal branch of the facial nerve in relation to fascial planes: an anatomic study. Plast Reconstr Surg. 2010;125(2):532-7. PMID: 20124839. doi:10.1097/PRS.0b013e3181c82e9d
  6. Pitanguy I, Ramos AS. The frontal branch of the facial nerve: the importance of its variations in face lifting. Plast Reconstr Surg. 1966;38(4):352-6. PMID: 5926990. doi:10.1097/00006534-196610000-00010
  7. Dingman RO, Grabb WC. Surgical anatomy of the mandibular ramus of the facial nerve based on the dissection of 100 facial halves. Plast Reconstr Surg Transplant Bull. 1962;29:266-72. PMID: 13886490. doi:10.1097/00006534-196203000-00005
  8. Ziarah HA, Atkinson ME. The surgical anatomy of the cervical distribution of the facial nerve. Br J Oral Surg. 1981;19(3):171-9. PMID: 6945121. doi:10.1016/0007-117x(81)90002-0
  9. Lewin ML, Tsur H. Injuries of the great auricular nerve in rhytidectomy. Aesthetic Plast Surg. 1976;1(1):409-17. PMID: 24173766. doi:10.1007/BF01570275
  10. McKinney P, Katrana DJ. Prevention of injury to the great auricular nerve during rhytidectomy. Plast Reconstr Surg. 1980;66(5):675-9. PMID: 7433552. doi:10.1097/00006534-198011000-00001
  11. Beleznay K, Carruthers JDA, Humphrey S, Jones D. Avoiding and treating blindness from fillers: a review of the world literature. Dermatol Surg. 2015;41(10):1097-117. PMID: 26356847. doi:10.1097/DSS.0000000000000486
  12. Beleznay K, Carruthers JDA, Humphrey S, Carruthers A, Jones D. Update on avoiding and treating blindness from fillers: a recent review of the world literature. Aesthet Surg J. 2019;39(6):662-74. PMID: 30805636. doi:10.1093/asj/sjz053
  13. Cho KH, Dalla Pozza E, Toth G, Bassiri Gharb B, Zins JE. Pathophysiology study of filler-induced blindness. Aesthet Surg J. 2019;39(1):96-106. PMID: 29873688. doi:10.1093/asj/sjy141
  14. DeLorenzi C. Complications of injectable fillers, part 2: vascular complications. Aesthet Surg J. 2014;34(4):584-600. PMID: 24692598. doi:10.1177/1090820X14525035
  15. Standring S, editor. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2020. Section 4, Head and neck, face and scalp; muscles of facial expression and their innervation. [A 43rd edition was published in 2024; either edition supports the material cited here.]
  16. Anatomy, Abdomen and Pelvis: Scarpa Fascia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Bookshelf ID: NBK553137. [Secondary source; cited for the superficial fascial system and the abdominal fat-layer scheme only.]
Episode 7: Regional VariationEpisode 9: When Skin Fails
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