{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T13:58:58Z","timestamp":1790949538667,"version":"4.1.0"},"reference-count":28,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T00:00:00Z","timestamp":1790899200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>The superficial musculoaponeurotic system (SMAS) is a fundamental concept in facial anatomy and surgery, but its organization within the human lips remains incompletely defined. This narrative review critically reassesses the anatomical evidence for a labial SMAS and its regional configuration. Published anatomical, histological, and imaging evidence was critically reviewed. The literature review is complemented by original qualitative histological and imaging observations of the human lips, included exclusively for morphological correlation with the published anatomical evidence and not as an independent quantitative study. The available evidence does not demonstrate a classical, readily separable laminar SMAS within the lips. Instead, it supports a three-dimensional connective tissue network extending from the oral mucosa to the skin and intimately incorporating the orbicularis oris muscle. This organization is associated with neurovascular structures and may have biomechanical and sensory implications, although these functional interpretations are not directly demonstrated by the present material. The labial connective tissue architecture differs from the classical laminar SMAS described in other facial regions and may represent its regional equivalent. Further three-dimensional anatomical studies are required to establish this interpretation conclusively. By defining the normal fibromuscular architecture of the lips and the limits of its visualization, this review provides an anatomical framework for interpreting lip imaging while emphasizing that a labial SMAS is not currently a validated diagnostic or prognostic marker.<\/jats:p>","DOI":"10.3390\/diagnostics16193208","type":"journal-article","created":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T13:39:34Z","timestamp":1790948374000},"page":"3208","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["The Human Labial Superficial Musculoaponeurotic System (SMAS): Anatomy, Imaging, and Biomechanical and Sensory Implications\u2014A Narrative Review"],"prefix":"10.3390","volume":"16","author":[{"given":"Jos\u00e9","family":"Mart\u00edn-Cruces","sequence":"first","affiliation":[{"name":"Master ENDORE, Departamento de Cirug\u00eda y Especialidades M\u00e9dico-Quir\u00fargicas, Universidad de Santiago de Compostela, 15705 Santiago de Compostela, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Estefan\u00eda","family":"del Roc\u00edo Ocampo Poma","sequence":"additional","affiliation":[{"name":"Facultad de Odontolog\u00eda, Universidad Cat\u00f3lica de Santiago de Guayaquil, Guayaquil 090101, Guayas, Ecuador"},{"name":"C\u00e1tedra Hispanoamericana de Investigaci\u00f3n en Implantolog\u00eda Cl\u00ednica y Pr\u00f3tesis Dental, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Santiago de Guayaquil\u2013SOADCO, Guayaquil 090101, Guayas, Ecuador"},{"name":"Grupo de Investigaci\u00f3n de Prevenci\u00f3n y Salud Oral, Universidad Cat\u00f3lica de Santiago de Guayaquil, Guayaquil 090101, Guayas, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8713-951X","authenticated-orcid":false,"given":"Luis Alberto","family":"Chauca Baja\u00f1a","sequence":"additional","affiliation":[{"name":"Facultad de Odontolog\u00eda, Universidad Cat\u00f3lica de Santiago de Guayaquil, Guayaquil 090101, Guayas, Ecuador"},{"name":"C\u00e1tedra Hispanoamericana de Investigaci\u00f3n en Implantolog\u00eda Cl\u00ednica y Pr\u00f3tesis Dental, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Santiago de Guayaquil\u2013SOADCO, Guayaquil 090101, Guayas, Ecuador"},{"name":"Facultad de Odontolog\u00eda, Universidad Bolivariana del Ecuador, Dur\u00e1n 092406, Ecuador"},{"name":"Facultad de Odontolog\u00eda, Universidad de Guayaquil, Guayaquil 090101, Guayas, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mirian","family":"Teul\u00e9-Trull","sequence":"additional","affiliation":[{"name":"Master ENDORE, Departamento de Cirug\u00eda y Especialidades M\u00e9dico-Quir\u00fargicas, Universidad de Santiago de Compostela, 15705 Santiago de Compostela, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3199-8200","authenticated-orcid":false,"given":"Patricia","family":"Cuendias","sequence":"additional","affiliation":[{"name":"Departamento de Morfolog\u00eda y Biolog\u00eda Celular, Grupo SINPOS, Universidad de Oviedo, Oviedo, Spain"},{"name":"Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias, 33011 Oviedo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1442-1095","authenticated-orcid":false,"given":"Yolanda","family":"Garc\u00eda-Mesa","sequence":"additional","affiliation":[{"name":"Departamento de Morfolog\u00eda y Biolog\u00eda Celular, Grupo SINPOS, Universidad de Oviedo, Oviedo, Spain"},{"name":"Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias, 33011 Oviedo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1276-0018","authenticated-orcid":false,"given":"Jos\u00e9 A.","family":"Vega","sequence":"additional","affiliation":[{"name":"Departamento de Morfolog\u00eda y Biolog\u00eda Celular, Grupo SINPOS, Universidad de Oviedo, Oviedo, Spain"},{"name":"Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias, 33011 Oviedo, Spain"},{"name":"Facultad de Ciencias de la Salud, Universidad Aut\u00f3noma de Chile, Santiago, Chile"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,10,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1097\/00006534-197607000-00013","article-title":"The superficial musculo-aponeurotic system (SMAS) in the parotid and cheek area","volume":"58","author":"Mitz","year":"1976","journal-title":"Plast. Reconstr. Surg."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"53","DOI":"10.2739\/kurumemedj.MS682008","article-title":"The Key Structure of the Facial Soft Tissue: The Superficial Musculoaponeurotic System","volume":"68","author":"Watanabe","year":"2023","journal-title":"Kurume Med. J."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"669","DOI":"10.1002\/ar.25324","article-title":"Proprioceptive innervation of the human lips","volume":"307","author":"Cuendias","year":"2024","journal-title":"Anat. Rec."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"152159","DOI":"10.1016\/j.aanat.2023.152159","article-title":"Exploring somatosensory innervation of the human lip: A focus on the vermilion","volume":"250","author":"Cuendias","year":"2023","journal-title":"Ann. Anat."},{"key":"ref_5","unstructured":"Whitney, Z.B., Jain, M., and Zito, P.M. (2024). Anatomy, Skin, Superficial Musculoaponeurotic System (SMAS) Fascia. StatPearls [Internet], StatPearls Publishing."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1293","DOI":"10.1097\/PRS.0000000000010820","article-title":"Intralabial Lip Compartments and Their Potential Clinical Relevance","volume":"153","author":"Cotofana","year":"2024","journal-title":"Plast. Reconstr. Surg."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"488","DOI":"10.1097\/00006534-198504000-00005","article-title":"The superficial musculoaponeurotic system in the upper lip: An anatomic study in cadavers","volume":"75","author":"Pensler","year":"1985","journal-title":"Plast. Reconstr. Surg."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1097\/00006534-198601000-00035","article-title":"Superficial musculoaponeurotic system in the upper lip","volume":"77","author":"Jost","year":"1986","journal-title":"Plast. Reconstr. Surg."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"258","DOI":"10.1007\/s00266-003-3065-3","article-title":"Anatomy of the SMAS revisited","volume":"27","author":"Ghassemi","year":"2003","journal-title":"Aesthetic Plast. Surg."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1016\/j.aanat.2018.04.009","article-title":"The existence of labial SMAS-Anatomical, imaging and histological study","volume":"218","author":"Scutariu","year":"2018","journal-title":"Ann. Anat."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"D\u00edaz-Flores, L., Guti\u00e9rrez, R., Garc\u00eda, M.P., Gonz\u00e1lez-G\u00f3mez, M., Rodr\u00edguez-Rodriguez, R., Hern\u00e1ndez-Le\u00f3n, N., D\u00edaz-Flores, L., and Carrasco, J.L. (2021). CD34+ Stromal Cells\/Telocytes in Normal and Pathological Skin. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22147342"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"623","DOI":"10.1016\/j.fsc.2011.07.006","article-title":"3D mechanical modeling of facial soft tissue for surgery simulation","volume":"19","author":"Mazza","year":"2011","journal-title":"Facial Plast. Surg. Clin. N. Am."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"6446","DOI":"10.1007\/s00266-026-06037-1","article-title":"Anatomical Distribution of the Superior and Inferior Labial Arteries: A Cadaveric, Systematic Review, and Meta-analysis Study","volume":"50","author":"Milla","year":"2026","journal-title":"Aesthetic Plast. Surg."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"152221","DOI":"10.1016\/j.aanat.2024.152221","article-title":"Morphofunctional and histological patterns of blood vessels in the superficial cervicofacial musculoaponeurotic system in midlateral face regions","volume":"253","author":"Cucu","year":"2024","journal-title":"Ann. Anat."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Ostrowski, P., Bonczar, M., Elsaftawy, A., Koziej, M., Szczepanek, E., Walocha, J., Bravo, C., Escobar, S., and Cotofana, S. (2026). The Blood Supply of the Lips: A Systematic Review and Meta-Analysis. Aesthetic Plast. Surg., Epub ahead of print.","DOI":"10.1007\/s00266-026-06064-y"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"a041231","DOI":"10.1101\/cshperspect.a041231","article-title":"The Role of Myofibroblasts in Physiological and Pathological Tissue Repair","volume":"15","author":"Schuster","year":"2023","journal-title":"Cold Spring Harb. Perspect. Biol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"108528","DOI":"10.1016\/j.pharmthera.2023.108528","article-title":"Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases","volume":"250","author":"Ezzo","year":"2023","journal-title":"Pharmacol. Ther."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Fan, Z., Deng, K., Wang, L., Fu, J., Ma, L., Tu, S., Li, J., Yao, K., Xu, Z., and Guo, Y. (2026). The role of extracellular matrix stiffness in regulating fibroblast behaviors and disease progression. Front. Immunol., 17.","DOI":"10.3389\/fimmu.2026.1849447"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1016\/j.cden.2022.02.005","article-title":"Lip Augmentation","volume":"66","author":"Ghasemi","year":"2022","journal-title":"Dent. Clin. N. Am."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"65e","DOI":"10.1097\/PRS.0000000000012772","article-title":"Ultrasound Evaluation of Lip Anatomy and Filler Placement: A Cross-Sectional Study of Injection Accuracy, Migration, and Demographic Variation","volume":"158","author":"Harris","year":"2026","journal-title":"Plast. Reconstr. Surg."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"e20240035","DOI":"10.1590\/0100-3984.2024.0035","article-title":"U-SMAS: Ultrasound findings of the superficial musculoaponeurotic system","volume":"57","author":"Zattar","year":"2024","journal-title":"Radiol. Bras."},{"key":"ref_22","first-page":"247","article-title":"Anatomo-radiological study of the superficial musculo-aponeurotic system of the face","volume":"112","author":"Macchi","year":"2007","journal-title":"Ital. J. Anat. Embryol."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Czumbel, L.M., Farkasdi, S., Gede, N., Mik\u00f3, A., Csupor, D., Luk\u00e1cs, A., Ga\u00e1l, V., Kiss, S., Hegyi, P., and Varga, G. (2021). Hyaluronic Acid Is an Effective Dermal Filler for Lip Augmentation: A Meta-Analysis. Front. Surg., 8.","DOI":"10.3389\/fsurg.2021.681028"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"23","DOI":"10.36849\/JDD.6304","article-title":"Lip Augmentation With Hyaluronic Acid Fillers: A Review of Considerations and Techniques","volume":"22","author":"Cooper","year":"2023","journal-title":"J. Drugs Dermatol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e70445","DOI":"10.1111\/jocd.70445","article-title":"Aesthetic Treatment of the Lips With Hyaluronic Acid Filler: The Multi Vector Lip Technique","volume":"24","author":"Menezes","year":"2025","journal-title":"J. Cosmet. Dermatol."},{"key":"ref_26","first-page":"9043","article-title":"Perspectives and challenges in lip rejuvenation: A systematic review","volume":"27","author":"Tabassum","year":"2023","journal-title":"Eur. Rev. Med. Pharmacol. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1016\/j.fsc.2007.08.008","article-title":"Perioral rejuvenation and lip augmentation","volume":"15","author":"Ali","year":"2007","journal-title":"Facial Plast. Surg. Clin. N. Am."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"624","DOI":"10.1097\/PRS.0b013e3181addc06","article-title":"The aging lip: A comparative histological analysis of age-related changes in the upper lip complex","volume":"124","author":"Penna","year":"2009","journal-title":"Plast. Reconstr. Surg."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/19\/3208\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T13:40:58Z","timestamp":1790948458000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/19\/3208"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,2]]},"references-count":28,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["diagnostics16193208"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics16193208","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,2]]}}}