Abstract

Cervical mucus plays critical roles in the reproductive process of several mammals, facilitating sperm ascent or acting as filter for sperm, among other functions. Some researchers have reported that mucus ultrastructure comprises a meshwork of parallel fibrillar subunits, while others suggest it comprises a mesh of interconnected filaments. The objective of this work was to study the ultrastructure of heifer cervical mucus obtained at estrus. Mucus samples were collected from 6 healthy Holstein-Friesian heifers and studied with scanning electron microscopy (SEM). For four heifers, micrographs clearly showed that, at estrus, the ultrastructure of cervical mucus consists mainly of a three-dimensional mesh of interconnected filaments with a large number of small pores (range: 0.11-1.40 µm). None of the SEM micrographs revealed arrangements with zones formed by parallel fibrillar subunits in the cervical mucus ultrastructures observed. For two heifers, mucus micrographs showed spherical or 'spongiform' structures which, most probably, correspond to artifacts originated in the critical point drying process or in the metallic coating prior to SEM observation. It can be concluded, therefore, that heifer cervical mucus ultrastructure obtained at the estrus stage consists mainly of a three-dimensional mesh of interconnected filaments in which a large number of small pores are present.