PHYSIOLOGY OF COITUS ::
Coitus is a biological act involving the introduction of sperms into the vagina through penis The events include erection of penis ejaculation of the semen orgasm in male and orgasm in female
Erection ::
Erection is necessary for the coitus and delivery of sperms in the female it is due to the engorgement of penis with blood The penis which is small flabby and covered with wrinkled skin in resting stage becomes thick elongated and rigid and thus well adapted for the introduction into vagina Erection of penis is a reflex phenomenon that occurs in man following the stimulation of glans penis related skin area or simply psychological stimulation The impulse pass along afferent nerves to integrating centres in the sacral region of the spinal cord There these impulses initiate impulses which travel back along parasympathetic fibres Excitation of parasympathetic fibres cause arterial dilatation in the penis so that the venous sinusoids of the corpora cavernosa and corpora spongiosum become engorged with blood producing erection During erection the secretion of the bulbo-urethral glands is discharged to lubrricate urethra
Ejaculation ::
This is also a reflex action involving movement (emission) of spermatozoa and glandular secretions into the urethra followed by the sudden ejection of the semen from the penis Emission of the glandular secretions occurs in a definite sequence Ejaculation is triggered by stimulation of tactile receptors in the glans penis Friction between the glans penis and the vaginal mucosa reinforced by other afferent streams and psychological factors generate impulses that are passed along afferent nerves to the centres in the lumbar region of the spinal cord from here impulses travel back along the sympathetic fibres The sympathetic activity leads to contraction of the smooth muscles of the epididymis vas-deferens and secretory glands propelling spermatozoa and glandular secretions into the urethra Simultaneously the internal sphincter of the urethra constricts perventing entry of semen in the bladder Contraction of bulbospongiosum and ischiocavernous muscles (muscles in the corpora cavernosa and corpus spongium )due to reflex activity in somatic motor nerves of spinal cord then lead to pulsatile emission of the seminal fluid from the urethra
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