Histological Description of the Interaction Between Muscle Fibers and Connective Tissue of the Fascia of the Human Trapezius Muscle

The skeletal muscle fascia corresponds to a condensation of connective tissue. Fascias are highly innervated and sensitive, and can cover non-expandable structures as well as musculature. It is suggested that fascias have a pivotal role in functions such as postural regulation, peripheral motor coordination and proprioception. Also, the presence of inflammation and microcalcification in fascia of patients with localized muscle pain has been described, suggesting a pathogenic role in pain. The aim was to describe the histological structure of the external deep fascia of the trapezius muscle, with emphasis on the content and arrangement of muscle fibers, type I collagen, and adipose tissue. Sample material was obtained from a male cadaver (60-70 years old), by dissection of the posterior cervical region of the superficial fascia of the trapezius muscle and fixed in buffered formalin. Samples were processed by routine histological techniques and embedded in paraffin, obtaining 5 mu m-thick sections that were stained according to the van Gieson technique. The trapezius fascia is composed of type I collagen, organized into high-density collagen bundles and oriented in different directions, and by adipocytes disposed in longitudinal groups on the main axis of the fascia. Muscle fibers are organized into bundles that are inserted laterally on the thickness of the fascia. It is possible that lateral transmission of tensional forces between the fibers might be present.