Anatomy, MRI And Serial Histological Sections To Three-dimensional Reconstruct Upper Lip Muscular System

[Objective]To observe the upper lip tissue in every direction, and to establish complete, precise,and three-dimensional upper lip muscular system model with anatomy, MRI, serial histological sections and three-dimensional reconstruction software.[Methods] Two adult cavader head specimens were dissected from skin to the deep layer.The radiated musculature of the upper lip contains the levator labii superioris alaeque nasi, the levator labii superioris, the zygomaticus minor, the zygomaticus major,the risorius, the levator anguli oris, the buccinator and the orbicularis oris. Enthesis and direction of these muscles were observed. The dissection and description were restricted to the intersection of these muscles. Eight adult cavader lip specimens were imbedded in the paraffin and serially sectioned in Axial plane, sagittal plane, coronal plane. And sections were stained with hematoxylin and eosin(HE), Masson trichrome to observe philtrum, Cupid’s bow, vermilion and nostril sill.The upper lip model was reconstructed with the medical3D reconstruction software such as3D-D0CT0R. And One adult cavader upper lip specimens was reconstructed with MicroMR. At last, three-dimensional upper lip muscular system model was to establish with all the information of above.[Results] From this upper lip muscular system model,we could clearly see the construction around the upper lip.There was not only paralleled muscle fibers of the orbicularis oris,but also flabellate muscle fibers from angle of lip. Some of which migrated to the nasolabialis at anterior nasal crest,some of which crossed the philtrum to the opposite side, migrated to the levator labii superioris alaeque nasi under the nasal floor,and migrated to the levator labii superioris and the zygomaticus minor near the red lip margin.The alar part of the nasalis muscle migrated with the contralateral orbicularis oris and connected with the lateral crura of alar cartilage.The nasolabialis migrated with the ipsilateral orbicularis oris and connected with the medial crura of alar cartilage. At the nostril sill, the alar part of the nasalis muscle intersected with the nasolabialis.The levator labii superioris and the zygomaticus minor entered the lip superolaterally in relation to the ala nasi and crossed inferomedially as oblique fibres to insert at or near the vermilion border of the orbicularis oris,which was important to the Cupid’s bow.Muscle fibres of the deep orbicularis oris inserted into the skin lateral to the contralateral philtrum ridge in Axial plane. Superficial reticular muscle fibres of the levator labii superioris, the zygomaticus minor, the zygomaticus major and the orbicularis oris which were similar to SMAS inserted into the skin medialis to the philtrum ridge in coronal plane.These two type muscle fibres intersected to form the philtrum.[Conclusions] Three-dimensional upper lip muscular system model was established with all the information of above.On the basis of this model, we discovered three tension equilibrium structure exist in the upper lip, and suggested the concept of chief tension zone,first assist tension zone and second assist tension zone.