Facial Muscles and Its Modiolus: A Review of Embryology, Comparative Anatomy, Morphology and Applied Anatomy

@#The modiolus of the face manifests the interesting landmark for facial muscles attachment. The strong connective tissue fibres play an important role in the clinical setting, especially in the aesthetic and dental surgeries. In the fourth week of intrauterine life, the development of the modiolus evolves in accordance with the growth of muscles of facial expression. Microscopically, a white, tendinous structure with the thick irregular collagenous connective tissue of collagen fibres predominance appeared to be the modiolus. Modiolus is morphologically a fibromuscular muscle situated on the lateral border of the mouth. The formation of the nasolabial fold is important and a well-developed modiolus provide a toned face. Several works of literature forementioned the number of facial muscles attached to the modiolus but no definitive similarity are identified. This review summarizes the updated morphological features and applied anatomy of the facial modiolus with its muscle attachment.

Comunicación preliminar acerca de la disposición morfológica, la funcionalidad y las implicancias clínicas del modiolo del ángulo oral (Modiolus anguli oris) / Preliminary communication about the morphological arrangement, functionality and clinical implications of modiolus of angulus oris (Modiolus anguli oris)

RESUMEN: La disposición anatómica de los músculos faciales es de una notable complejidad y requiere de un estudio pormenorizado para lograr su reconomiento preciso. La comprensión de la disposición morfológica y la funcionalidad del modiolo del ángulo oral (Modiolus angulis oris) es de gran relevancia al momento de analizar la constitución muscular de la comisura labial, y para comprender clínicamente las lesiones del ángulo de la cavidad oral, lo que permitirá un abordaje terapéutico adecuado, crucial para la preservación y reconstitución de la armonía facial.

SUMMARY: The anatomical arrangement of the facial muscles is of considerable complexity and requires a detailed study to achieve its precise recognition. The understanding of the morphological disposition and the functionality of the angle of the mouth (Modiolus angulis oris) is of great relevance when analyzing the muscular constitution of the labial commissure, and to understand clinically the injuries of the angulus oris, what that will allow an adequate therapeutic approach, crucial for the preservation and reconstitution of facial harmony.

The Location of the Modiolus in Living Korean / 체질인류학회지

Modiolus is convergence of the facial muscles at the angle of the mouth, and its shape and size varying with individual, age, sex and ethnicity. In the previous study, the modiolus was usually located under the horizontal line at the mouth angle. In most medical schools, the cadavers are of later ages and their facial muscles have lost their elasticity as they got older. The purpose of this study is to identify the location of the modiolus in live young Korean and to compare it with that of Korean cadavers from the previous study. Participants were one hundred students of the catholic medical school with a mean age of 24 years. Experimenter palpated the modiolus of each student with thumb and index finger. The average young live Korean modiolus was located at 14.4 mm lateral to mouth angle and 1.6 mm below the horizontal line of the mouth angle. Commonly, it is located below the mouth angle in 124 sides (62%). There was difference between horizontal distance of female and of male, and vertical distance of right and of left. The location of the modiouls was symmetric in 67%. These results were consistent with the previous study using Korean cadavers. Therefore these results suggest that the location of the modiolus is below to the mouth angle in large number of Koreans.

Location of the Modiolous and the Morphologic Variations of the Risorius and Zygomaticus Major Muscle Related to the Facial Expression in Koreans / 체질인류학회지

Location of the modiolous and morphological variations of the risorius and zygomaticus major muscles are related to the facial expression. The zygomaticus major, levator labii superioris, depressor labii inferioris, depressor anguli oris, risorius, orbicularis oris, buccinator and levator anguli oris muscles insert on the lateral border of the lip, forming the modiolus and mutually associating each other for functioning. The knowledge of the location of the modiolus and surrounding structures are essential to anatomy, prosthodontics, linguistic, physiology and computer simulation based on facial expressions. The authors examined the location of the modiolus, the morphological variations and anatomical relationship of risorius and zygomaticus major muscle to understand the features of the smile of Korean by dissecting 39 cadavers. The location of the modiolus can be showed as three types, according to their height related to the intercheilion horizontal line. Type A that modiolus locate at the intercheilion line was shown in 20 sides (26.0%), type B that modiolus locate above the intercheilion line was shown in 12 sides (15.6%), then type C that modiolus locate under the intercheilion line was shown in 45 sides (58.4%). Most modioli located at 10 ~20 mm lateral to the mouth corner and 0 ~10 mm below the intercheilion line. The risorius muscle was classified into five types by directions of muscle fibers. The depressor anguli oris -risorius type (type I) was observed in 31 sides (40.2%), the platisma -risorius type (type II) was observed in 30 sides (39.0%). Previously, it has been known that zygomaticus major muscle attaches to the modiolus mainly as one bundle. However, the results were clearly shown that two bundles of the zygomaticus major muscle attaches to the modiolus and the position of the mouth edge in 18 sides (23.4%). To sum it up, facial expression is of fundamental importance concerning the morphological variations and these results also can be considered for the facial reconstruction surgery and computer animation department.