The cervix and its mucus.
D055592:Biophysical Phenomena; D001703:Biophysics; D002582:Cervix Mucus / Q000032:analysis / Q000502:physiology*; D002584:Cervix Uteri / Q000002:abnormalities / Q000166:cytology; D003075:Coitus; D005260:Female; D006801:Humans; D007247:Infertility, Female / Q000175:diagnosis / Q000209:etiology* / Q000628:therapy; D008297:Male; D008722:Methods; D013083:Sperm Transport; D007507:Therapeutic Irrigation; D002577:Uterine Cervical Diseases / Q000150:complications