MORFOLOGIA DEL MUSCULO PTERIGOIDEO LATERAL ASOCIADO AL CONDILO MANDIBULAR EN LA ETAPA PRENATAL HUMANA MORPHOLOGY OF THE LATERAL PTERYGOID MUSCLE ASSOCIATED TO THE MANDIBULAR CONDYLE IN THE HUMAN PRENATAL STAGE

Miriam Carranza¹, Carmen Carda, Alicia Simbrón, María Sánchez Quevedo, Gabriela Celaya², María Elsa Gómez De Ferraris¹
unpublished
RESUMEN El músculo pterigoideo lateral (MPL) establece una relación directa con el cóndilo y el disco articular, desempeñando un rol importante en el movimiento mandibular a través del Com-plejo Articular Témporomandibular (CATM). El objetivo de este trabajo fue determinar la correspondencia entre las carac-terísticas morfológicas de los haces musculares del MPL y el grado de mineralización del cóndilo mandibular en la etapa prenatal, mediante un análisis estructural, ultraestructural y
more » ... tructural y microanalítico. Se utilizaron 16 fetos humanos de 11 a 37 sema-nas de gestación procedentes de abortos espontáneos y sin patologías aparentes. Se obtuvieron muestras del músculo pte-rigoideo lateral y cóndilo mandibular para ser examinados mediante microscopía óptica, electrónica y técnicas de micro-análisis. Muestras incluidas en parafina se emplearon en los estudios de inmunomarcación con desmina (dilución 1: 25 Dako) y alfa actina sarcómerica (dilución 1:50 Dako) visuali-zados con sistema avidina-biotina. El lado contralateral de cada una se utilizó para microscopía electrónica de transmi-sión. En cuatro cóndilos de 17 y 21 semanas del desarrollo se analizó el contenido relativo de calcio y fósforo con la técnica microanalítica por difracción de rayos X. Entre las 11 y 16 semanas el MPL estuvo constituído por mio-tubos secundarios asociados a células satélites y fascículos ABSTRACT The lateral pterygoid muscle (LPM) inserts at the condyle and the articular disc and plays a central role in mandibular movement via the Temporomandibular Articular Complex. The aim of this study was to examine the association between the morphology of LPM muscular fascicles and the degree of mineralization of the mandibular condyle in the prenatal stage employing structural, ultrastructural and microanalytical evaluation. Sixteen human fetuses at 11-37 weeks of gestation, with no apparent pathology and resulting from spontaneous abortions , were included in the study. Samples from lateral pterygoid muscle and the mandibular condyle were processed for light microscopy and electron microscopy and microanaly-sis. Desmin immunolabeling (dilution 1: 25 Dako) and alpha sarcomeric actin immunolabeling (dilution 1:50 Dako) employing the avidin-biotin system were used in paraffin embedded samples. Contralateral samples were examine by transmission electron microscopy. Four condyles (at 17-21 weeks of gestation) were used to measure the relative content of calcium and phosphorous employing the X-ray diffraction microanalytical technique. At 11-16 weeks of gestation, the LPM was composed of secondary myotubes associated to satellite cells and nerve fibers. At 18 weeks, the muscle exhibited multiple compact fascicles and the condyle showed a thin, external, subperiostal mineral-ized layer with few central bone spicules. At 20 weeks, at the site of insertion of the LPM, the bone trabeculae of the condyle contained an electrondense matrix with abundant mineraliza-tion nuclei. At 17-21 weeks of gestation no significant variations in the contents of phosphorous and calcium were observed. At 24 weeks, transmission electron calcium and microscopy studies revealed a marked increase in the functional units of the muscle fascicles. Also, at this age muscle fibers exhibited differences in the expression of desmin and alpha sar-comeric actin. At 37 weeks the muscle became multipennate in appearance, exhibiting a more complex organization than younger fetuses. Alpha sarcomeric actin labeling became light with age. This results suggest that between 16 and 22 weeks of gestation the differentiation and maturation process of the muscle fibers precedes and prevails over the development and mineraliza-tion process from mandibular condyle. The rudimentary performance of the prenatal LPM would be one of the factors that regulate the process of ossification at the level of the mandibular condyle. The rate of ossification would increase starting from 22 of gestation week.
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