INTERACTIONS OF THE UTERUS AND SEMEN

At the time of breeding, large numbers of spermatozoa enter the uterus . Only a small proportion of them are transported to the oviducts. The majority of the sperms is to become destroyed. By some unknown mechan isms, fertile spermatozoa that are at the right maturational stage are selected over others. They are rapidly transported to the oviducts by uterine contractions. Spermatozoa elicit an inflammatory reaction in the uterus which includes the chemotaxis of leukocytes. The intensity of inflammation depends on semen concentration and/or presence or abse nce of seminal plasma. Seminal plasma suppresses inflammation and leuk ocyte chemotaxis, live and dead sperm provoke a similar inflammatory r esponse. Neutrophils and macrophages phagocytize spermatozoa. Sperm re mnants are removed by lymphatics and through the open cervix, driven b y uterine contractions. Although only one spermatozoa fertilizes the e gg, the presence of several others is required. Even dead spermatozoa seem to fulfill this task.