MORPHOLOGICAL FEATURES AND MORPHOMETRIC PARAMETERS OF HUMAN FETAL THYMUS GLANDS

Introduction: Thymus is one of the central lymphoid organs. It plays an important role in the differentiation, selection and maturation of T-lymphocytes. In the recent years morphology and morphometry of the thymus gland in the newborn is gaining significance as it demonstrates great variability between individual infants and in the same infant at different times. Materials and methods: In the present study 45 thymus specimens from aborted human fetuses of 16 to 40 weeks gestational age and both sexes were studied by autopsy for morphological and morphometric features. The morphometric parameters were measured using pachymeter. Results: The thymus gland was located in the superior mediastinum. 60% (27/45) specimens showed cervical extensions. Brachiocephalic vein anterior to thymus was observed in 3 cases which is an important anomaly to be observed in thymectomy procedure. Thymuses were greyish pink to greyish brown in colour. Variations were also observed in the number of lobes of glands in which one is single lobed, most of the glands are bilobed and few are trilobed. There is progressive increase in all morphometric dimensions of the thymus in relation to gestational age. Most of the specimens were less than 4cm in length. Half of the specimens were below 2cm in width and other half were 2.0 to 5.0 cm in width. For 90% of the specimens thickness of the organ was less than 0.5cm. The thymus gland was 0.2% of fetal body weight. Conclusion: The morphological observations of thymus gland shows great variations which has to be considered in thymectomy. In addition to anthropometric parameters of fetus, morphometric parameters of thymus glands present significant relation to the gestational age of fetuses. It is possible to determine the thymic morphometric parameters in relation to gestational age.