ejaculation /-ā″shən/ [L, ejaculari, to hurl out] , the sudden emission of semen from the male urethra, usually during copulation, masturbation, or nocturnal emission. It is a reflex action in two phases. In the first phase, sperm, seminal fluid, and prostatic and bulbourethral gland secretions are moved into the urethra. In the second phase, strong spasmodic peristaltic contractions force ejaculation. The sensation of ejaculation is commonly also called orgasm. The fluid volume of the ejaculate is usually between 2 and 5 mL. Each milliliter usually contains 50 million to 150 million spermatozoa. −ejaculatory, adj.
