Anatomy arnd physiology of ejaculation

Abstract

The human (female and male) sexual response was described by Masters and Johnson [59] as including four interactive phases: excitation, plateau, orgasm, and resolution. This definition has been subsequently revised by Kaplan [40] and Levin [50] to lead to a model widely accepted, consisting of desire, excitation, orgasm, and resolution. The different aspects of male sexual function include sexual desire, erection, ejaculation, and orgasm. Each of these phases is controlled by a complex and coordinated interplay of multiple components of the brain, spinal cord, and relevant peripheral organs. Ejaculation is the final stage of coitus in mammalian males since it is followed by a refractory period during which sexual responses are inhibited. Ejaculation consists in the synchronized succession of physiological events that form two distinct phases: emission and expulsion. Emission corresponds to the secretion of the different components of the seminal fluid from accessory sex glands and testes. The seminal secretions are poured into the posterior urethra via phasic contractions of the glands and their respective ducti while the bladder neck is firmly closed to prevent backflow into the bladder. Expulsion is then triggered in the form of an intense burst of contractions of pelviperineal striated muscles. These two phases are intimately linked but they can be studied distinctively using specific physiological markers and can occur independently from each other in peculiar experimental paradigms and pathophysiological conditions.