Anatomical and histological study of human deep fasciae development

To characterize the connective tissue found between the subcutaneous adipose tissue and the underlying muscle tissue in different regions and at different stages of human fetal development. We aim to identify its structural similarities to adult deep fascia, and to establish its role in myofascial development. Samples from the arm, forearm, low back and thigh regions (from sites topographically homologous to the adult deep fascia) of five fetus body donors were obtained to perform gross anatomy dissection and histologic sections. Sections were stained with hematoxylin-eosin and Masson trichrome stain to observe their overall structure. Antiserum to protein S100 was used to analyze the presence and distribution of nerve fibers, and immunohistochemistry processing with Tcf4 marker was used to ensure fibroblast activity. Gross anatomy and histological sections of fetal samples showed the presence of connective tissue topographically and morphologically equivalent to adult deep fasciae. Developing blood vessels and nerves were found evenly distributed within the connective tissue during early development and in the portion adjacent to the muscle at later stages. The presence of Tcf4+ fibroblasts was confirmed in all analyzed mesenchymal connective tissue. Deep fascia is present from week 21 of human development in the lower back and upper and lower limbs. Blood vessels and nerves develop parallel to it and occasionally cross it from the deep to superficial plane. The presence of Tcf4+ fibroblasts in the deep fascia suggests a crucial role for this structure in muscle morphogenesis.