Ejaculation and its disorders.
Ejaculation is the final link of the male sexual function chain "Libido--Erection--Penetration--Achievement of Climax--Ejaculation". Each link is highly androgen-dependent. Although the initiation of a subsequent link is normally dependent on achievement of the previous link, each link has its own mechanisms, and can be made to occur in isolation. The basic requirements for ejaculation are the production of seminal fluid (mostly from the seminal vesicles) and its propulsion. The production of a normal volume of seminal fluid requires the presence of seminal vesicles and the maintenance of their secretion by androgens. The propulsion of seminal fluid is in 3 phases: I. Contraction of seminal vesicles; II. Closure of bladder neck (both due to T9-L2 sympathetic stimulation); III. Expulsion of semen from the bulb of the urethra (due to S2-S3 somatic stimulation). The coordination of these phases is probably at hypothalamic level. Failure of ejaculation may be classified into I. Deficiency of production of seminal fluid from (1) Absence of seminal vesicles or (2) Androgen deficiency from (a) Pituitary dysfunction or (b) Testicular interstitial-cell failure from a number of causes. Correction of androgen deficiency usually restores ejaculation.