Abstract

PIP: Sperm transport in the female reproductive tract involves 3 stages: rapid short sperm transport; colonization of reservoirs; and slow prolonged release. Sperm transport through the cervix is affected by contractile activity of vagina and cervix, properties of cervical mucus, directional motility of sperm and possibly female orgasm, in addition to other endocrine, hereditary, immunological and psychological factors. Aided by myometrial contraction, spermatozoa may reach the site of fertilization within 2 to 10 minutes. During transport in the female tract, the sperm are separated from the seminal plasma and resuspended in endometrial and oviductal fluids, reducing the survival time of sperm. In artificial insemination, the physicochemical and immunological factors in the vagina and cervix affect sperm survival and transport into the uterus and oviduct. Spermatozoa are immobilized by vaginal secretions within 1 to 2 hours of insemination, suggesting the importance of rapid transport of sperm in the fertilization process. During ovulation, the cervical mucus provides an environment favorable to sperm survival; the biochemical changes which occur include decrease in albumin, alkaline phosphatase, peptidase, antitrypsin, esterase and sialic acid, as well as an increase in mucins and NaCl. The main cervical mucus components which are favorable to sperm survival have not been identified, although hexosamines and carbohydrate forms are suspected of contributing to sperm survival in the cervix.