men s health issues
Overview of Sexual Function and Dysfunction in Men
Normal Male Sexual Function
Normal sexual function is a complex interaction involving both the mind and the body. The nervous, circulatory, and endocrine (hormonal) systems all interact with the mind to produce a sexual response. A delicate and balanced interplay among these systems controls the male sexual response. Desire(also called sex drive or libido) is the wish to engage in sexual activity. It may be triggered by thoughts, words, sights, smell, or touch. Desire leads to the first stage of the sexual response cycle, excitement. Excitement,or sexual arousal, follows. During excitement, the brain sends nerve signals down the spinal cord to the penis. The arteries supplying blood to the erectile tissues (corpora cavernosa and corpus spongiosum) respond by opening wider (relaxing and dilating). The widened arteries dramatically increase blood flow to these areas, which become engorged with blood and expand. This expansion exerts pressure that compresses the veins that normally drain blood from the penis, slowing the outflow of blood and thus elevating blood pressure within the penis. This elevated pressure in the penis results in rigidity and erection. Also, muscle tension increases throughout the body. In theplateau stage,excitement and muscle tension are intensified. Orgasmis the peak or climax of sexual excitement. At orgasm, muscle tension throughout the body further increases and the pelvic muscles contract, followed by ejaculation. Ejaculationresults when nerves stimulate muscle contractions in the male reproductive organs: the seminal vesicles, prostate gland, and the ducts of the epididymis and vas deferens. These contractions force semen into the urethra. Contraction of the muscles around the urethra further propels the semen out of the penis. The neck of the bladder also constricts, preventing semen from flowing backward into the bladder. Although ejaculation and orgasm often occur nearly simultaneously, they are separate events. Rarely, ejaculation can occur without orgasm. Also, orgasm can occur in the absence of ejaculation, especially before puberty, or as a side effect of certain drugs (such as antidepressants) or after surgery (such as removal of the colon or prostate gland). Orgasm is normally highly pleasurable. In theresolution stage,the body returns to an unaroused state. Once ejaculation takes place or orgasm occurs, penile arteries constrict and the smooth muscle of the corpora cavernosa and corpus spongiosum contracts, reducing blood inflow, increasing blood outflow, and causing the penis to become limp (detumescence). After orgasm, erection cannot be obtained for a period of time (refractory period), often as short as 20 minutes or less in young men but longer in older men. The time between erections generally increases as men age. 