Anatomical Variability of Fascial-Muscle Formations of the Thorax in 4-6-Month Human Fetuses

The development of rational accesses and methods of surgical interventions to the chest walls, muscles and vascular-nerve formations of the chest involves clarifying data on the topography of fascia, superficial and deep muscles of the chest at different stages of human ontogenesis. The purpose of the study. Identification of macromicroscopic structure and topography of fascia and chest muscles in 4-6-month human fetuses. Materials and methods. The study was performed using microscopy of a series of consecutive histological sections of 29 human embryos of 81.0-230.0 mm parietal-coccygeal length, production of three-dimensional reconstruction models and morphometry. Results and discussion. In some early fetuses, and in isolated cases in the same fetus, there is anatomical variability of the pectoralis major muscle, characterized by asymmetry of shape, size and topography of individual parts of the right and left pectoralis major muscles. The underdevelopment of the individual muscle bundles of the sternocostal part of the pectoralis major muscle, hypoplasia of the internal intervertebral muscles, aplasia of the external intercostal membrane, internal intercostal and subcostal muscles, transverse muscles of the chest is described. Conclusion. In human fetuses of 4-6 months old there is anatomical variability of the chest muscles, characterized by bilateral asymmetry, variability of shape, size and topography of both their individual parts and muscle as a whole. In early human fetuses, thoracic fascia is a rather thin structural plate, in the structure of which there is no layering. Intervertebral spaces at the level of rib cartilage are filled with internal intervertebral muscles, the fibers of which near the edges of the thorax have a vertical direction, and from the point of connection of the rib cartilage to the thorax – oblique. In the gap between the external and internal intervertebral muscles of fascia as such is not manifested, but only a small layer of loose fiber is determined, in which the vascular-nerve bundles pass. In the fetuses of 6 months, the endothorаcic fascia on the posterior wall of the chest is somewhat thickened, split into separate plates and forms fascial cases for vascular-nerve formations located near the spinal column