Andrology: A scientific or medical discipline concerning the study of male reproductive biology, diseases of the male genital organs, and male infertility. Major areas of interest include ENDOCRINOLOGY; SPERMATOGENESIS; semen analysis; FERTILIZATION; CONTRACEPTION; and CRYOPRESERVATION.Urology: A surgical specialty concerned with the study, diagnosis, and treatment of diseases of the urinary tract in both sexes, and the genital tract in the male. Common urological problems include urinary obstruction, URINARY INCONTINENCE, infections, and UROGENITAL NEOPLASMS.Prostatic Diseases: Pathological processes involving the PROSTATE or its component tissues.Infertility, Male: The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.Antispermatogenic Agents: Agents, either mechanical or chemical, which destroy spermatozoa in the male genitalia and block spermatogenesis.Semen Analysis: The quality of SEMEN, an indicator of male fertility, can be determined by semen volume, pH, sperm concentration (SPERM COUNT), total sperm number, sperm viability, sperm vigor (SPERM MOTILITY), normal sperm morphology, ACROSOME integrity, and the concentration of WHITE BLOOD CELLS.Semen: The thick, yellowish-white, viscid fluid secretion of male reproductive organs discharged upon ejaculation. In addition to reproductive organ secretions, it contains SPERMATOZOA and their nutrient plasma.Tripterygium: A plant genus of the family CELASTRACEAE that is a source of triterpenoids and diterpene epoxides such as triptolide.Sperm Count: A count of SPERM in the ejaculum, expressed as number per milliliter.Work Simplification: The construction or arrangement of a task so that it may be done with the greatest possible efficiency.Spermatozoa: Mature male germ cells derived from SPERMATIDS. As spermatids move toward the lumen of the SEMINIFEROUS TUBULES, they undergo extensive structural changes including the loss of cytoplasm, condensation of CHROMATIN into the SPERM HEAD, formation of the ACROSOME cap, the SPERM MIDPIECE and the SPERM TAIL that provides motility.Sperm Motility: Movement characteristics of SPERMATOZOA in a fresh specimen. It is measured as the percentage of sperms that are moving, and as the percentage of sperms with productive flagellar motion such as rapid, linear, and forward progression.Erectile Dysfunction: The inability in the male to have a PENILE ERECTION due to psychological or organ dysfunction.