Análise evolutiva da morfologia e irrigação do timo de Javali (Sus scrofa Linnaeus, 1758)

Abstract

The boar (Sus scrofa Linnaeus, 1758) is a suid native from North Africa and southwest Asia. As an ancestor of the domestic pig, the objective was to describe comparatively the arteries responsible for the irrigation of the cervical, thoracic and middle lobes of the boar thymus, determining also the morphological characteristics of this organ in this species to correlate them evolutionarily with the representatives of the Suidae family. Twelve boar fetuses belonging to the Animal Anatomy Laboratory of the Universidade Federal de Uberlândia, Minas Gerais, were used. The long right and left cervical thymic lobes received branches distributed through the right and left common carotid arteries and right and left superficial cervical arteries and sometimes through the left external thoracic arteries, and left subclavian artery. The irrigation of right and left trapezoidal thoracic thymic lobes was performed predominantly by direct and indirect ipsilateral and contralateral branches of the right and left internal thoracic arteries and also by branches of the left and right subclavian arteries. This distribution was maintained along the evolution being present in more recent lines and races of suids characterizing thus a synapomorphic condition. Direct and indirect branches of the right and left superficial cervical arteries and direct branches of the right internal thoracic artery were found for the middle thymic lobe, which is a unique description in this species, demonstrating a primitive evolutionary characteristic in this ancestor. The 83-day-old boar fetuses had a length of 20.66 cm from the base of neck to base of tail, which allowed us to correlate it with the size of the right and left cervical thymic lobes, which were on average equivalent to 2.75 cm. The average length of the middle thymic lobe was 0.4 cm in ten animals (100.00%). The right and left thoracic thymic lobe of ten specimens (100.00%) presented an average of 1.68 cm. The histological characteristics of a fetus with an average age of 85 days ensure the topographic characterization and subdivision of the thymic lobes in cervical, middle and thoracic, since the identification of the cell types and location in the cortical, medullar, capsular regions, and interlobular septa. Concentric aggregates called thymic corpuscles were clearly visualized in the medullary region of the cervical, middle, and thoracic thymic lobes.