Histological Study Of The Normal Infant Philtrum

[Objective]To observe the normal infant philtrum by different histological methods,and to explore the architectural basis for the philtrum.[Methods]Eleven nomal upper lips of infant cadavers were used. Serial sections were obtained in the axial,sagittal,and coronal planes with the Masson staining with three specimens.Reconstruction was done with three-dimensional softwares (eg,3D-Doctor,3Dmax).Four different sagittal sections were made on the midline of the philtral dimple,bilateral philtral ridge,and the midlateral side with three specimens.Three different axial sections were made on the upper,middle,and lower upper lip with three specimens.The above sections were stained with HE and Masson.We measured the thickness of the dermis and muscle and observed the direction of the orbicularis oris muscle.Two specimens were used to make serial sagittal sections at the midline of the philtral dimple,unilateral philtral ridge,and the midlateral side.Myosin heavy chains-fast(MHCf) and myosin heavy chains-slow(MHCs) antibodies were used to determinate the fast and slow skeletal muscle fibers.[Results]1.The relationship of the thickness of the dermis and philtrum:The thickness of the dermis has no significant difference in the axial and sagittal planes(P>0.05).2.The relationship of the the thickness of the muscle and philtrum:The muscle at philtral ridge is obviously thicker than the muscle at philtral dimple(P<0.05).3.The observation of the direction of the muscle:The orbicularis oris muscle has two major subdivisions:deep/superficial.The deep muscle is composed of pars peripheralis and marginalis.Fibers of pars peripheralis decussate at the midline and insert into the contralateral philtral ridge dermis. They also combine the superficial fibers to be a muscle complex to increase the thickness of the philtral ridge.4.The muscle fibers of the different subdivisions:The superficial is composed of fast fibers (98.30%) and slow fibers (1.13%).The pars peripheralis is composed of fast fibers (95.30%) and slow fibers (3.14%).The pars marginalis is composed of fast fibers (91.31%) and slow fibers (5.74%).The percentage of the slow fibers in pars marginalis is much higher than in pars peripheralis(P=0.002).The percentage of the fast fibers in superficial is much higher than in pars marginalis and peripheralis(P=0.000).5.The muscle fibers of the different place in superficial and pars peripheralis:The superficial at philtral dimple is composed of fast fibers (95.88%) and slow fibers (2.41%).The superficial at philtral ridge is composed of fast fibers (98.52%) and slow fibers (1.11%).The superficial at the midlateral side is composed of fast fibers (99.07%) and slow fibers (0.66%).The percentage of the fast fibers in the midlateral side of superficial is much higher than in philtral ridge(P=0.030).The percentage of the fast fibers in the philtral ridge of superficial is much higher than in philtral dimple(P=0.001).The pars peripheralis at philtral dimple is composed of fast fibers (93.94%) and slow fibers (4.19%). The pars peripheralis at philtral ridge is composed of fast fibers (94.49%) and slow fibers (3.84%).The pars peripheralis at the midlateral side is composed of fast fibers (95.79%) and slow fibers (2.70%).All the percentage of the fast and slow fibers has no significant difference(P>0.05).[Conclusions]1.The orbicularis oris muscle has two major subdivisions:deep/superficial.The deep muscle is composed of pars peripheralis and marginalis.All subdivisions have different percentage of the fast and slow muscle fibers.2.The philtrum is independent of the thickness of the dermis.3.The dermal insertion of pars peripheralis and the muscle complex may be the architectural basis for the philtral ridges.4.The philtral dimple reflects absence of the dermal insertion.5.The philtum is probably relative to the different percentage of the fast and slow fibers.