the collagen (type III) fibers forming the distinctive loose connective tissue stroma of embryonic tissues, mesenchyme, red pulp of the spleen, cortex and medulla of lymph nodes, and the hematopoietic compartments of bone marrow; they account for a substantial portion of the collagen fibers of the skin, liver, blood vessels, synovial membrane, uterine tissue, and granulation tissue; characterized by organization as a reticular meshwork of fine filaments and by an affinity for silver and for periodic acid-Schiff stains.
