Structural aspects of human cervical mucus

Two types of fibrous structures can be demonstrated in midcycle cervical mucus: (1) long, thick fibers that vary in diameter from 0.5 to 5 μm and run parallel to each other, and (2) microfibrils that vary in diameter from 500 to 1,500 Å and form bundles or networks. The spaces in such networks usually measure from 800 to 4,000 Å. The fibers are made up of the microfibrils and most likely represent the micelles that give spermatozoa their directional transport through the cervix.