Anatomy & Physiology

Anatomy & Physiology Study Guide

25.8 Sexual Function The autonomic nervous system influences male and female sexual function. Sexual intercourse , also known as coitus or copulation, is the physical act of the penis being received by the vagina for the purpose of introducing semen into the female reproductive tract. Male Sexual Function During sexual arousal, erotic thoughts stimulate sensory nerves in the genital region. This causes increased blood flow to the pelvis area, and subsequent outflow to the genitals leads to erection of the penis. The integument covering the glans of the penis contains numerous sensory receptors, and the skin is tensed and sensitivity heighted. Subsequent stimulation can initiate the secretion of the bulbo-urethral glands, providing lubrication for the penile urethra and the surface of the glans. Intercourse stimulates the sensory receptors of the penis, and eventually, this stimulation results in the coordinated processes of emission and ejaculation. Emission occurs under sympathetic stimulation. The process begins when the peristaltic contractions of the ampulla push fluid and spermatozoa into the prostatic urethra. The combination moves the seminal mixture into the membranous and penile portions of the urethra. Powerful, rhythmic contractions of ejaculation appear in the penile muscles. Contraction of the smooth muscle within the prostate acts to pinch off the urethra, preventing the passage of urine through the erect penis. Ejaculation is associated with intensely pleasurable sensations; an experience known as male orgasm . After ejaculation, blood begins to leave the erectile tissue, and the erection begins to subside. This process is called detumescence . Arousal, erection, emission, and ejaculation are controlled by both the sympathetic and parasympathetic divisions of the autonomic nervous system. Any physical or psychological factor that affects a single component of the system can result in male sexual dysfunction called impotence . Fem le Sexual Function The events in female sexual function are comparable to those of male sexual function. During sexual arousal, an engorgement of the erectile tissues of the clitoris and increased secretion of cervical mucus glands occurs. At this time, a network of blood vessels in the vaginal walls becomes filled with blood. Fluid moves across the vaginal epithelium from underlying connective tissues. The rhythmic contact of the penis with the vaginal walls and clitoris during intercourse, reinforced by touch sensations from the breasts and other stimuli (visual, olfactory, and auditory), provides stimulation that leads to orgasm. Female orgasm is accompanied by peristaltic contractions of the uterine and vaginal walls. The threat of infection with a variety of microorganisms is possible with sexual activity. The consequences of such an infection may range frommerely inconvenient to potentially lethal. Sexually transmitted diseases (STDs) are transferred from individual to individual, primarily or exclusively by sexual intercourse.

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