1. NAME: OLASOJI C. FUNMI MATRIC NO: 14/MHS02/058 DEPARTMENT: NURSING SCIENCES COURSE CODE: PHS 212 LECTURER: MR TOBA

2. DEFINITION OF ERECTION AND COITUS An erection (clinically; penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firmer, engorged and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is often associated with sexual arousal or sexual attraction, although erections can also be spontaneous. Coitus is the sexual intercourse between a male and a female until orgasm and ejaculation occur. THE PHYSIOLOGY OF ERECTION AND COITUS A multiple step process is necessary to obtain an erection. The first step is tumescence. The two major physiological events in tumescence are arterial and arteriolar vasodilation, which causes increased blood flow to the lacunar spaces and simultaneous relaxation of the sinusoidal smooth muscle, allowing for distension. The second step is veno-occlusion that causes rigidity of the penis. The increase in blood flow actually raises pressure in the male organ and compresses the subtunica venular plexus between the tunica albuginea and the peripheral sinusoids, thus reducing

3. the venous outflow. The tunica is stretched to its capacity, and the emissary veins between the inner circular and the outer longitudinal layers are occluded, with a decrease in the venous outflow to a minimum. At this point there is an increase in partial pressure of oxygen(to about 90mmHg) and in intravenous pressure(around 100mmHg) that brings the penis to its erect state. The third step, the sensory organs detect anal stimulation, skin stimulation, perinea stimulation as well as friction on the glans penis. All of these sensations are transmitted via the pudendal nerve to the sacral plexus. In both sexes, the psyche is important,i.e. thinking, dreaming, fantasizing about things of a sexual nature enhances the stage of arousal. Ultimately, this all leads to orgasm in the female and ejaculation in the male. The physiology of male erection depends upon the degree of sexual stimulation he or she is receiving. Erection is caused by parasympathetic impulses from the sacral cord(S2, S3, S4) to the penis. Cowper’s glands secrete mucous through the urethra. This mucous washes out residual urine in the urethra and increases the pH for the sperm(sperm require an alkaline pH for survival). Cowper’s glands are small aid to lubrication for coitus as they only secrete 2-3 drops of lubricant. Most of the lubrication for coitus is from the female. Without lubrication, the sexual sensations are decreased and pain is sensed.

4. The scrotum contracts and the testes increase about 50% in size and elevate more. The penis changes colour due to vasocongestion from “skin colour” to pink to bright or deep red. There are numerous chemical transmitters involved in creating an erection which includes;  Epinephrine  Norepinephrine  Acetylcholine  Prostaglandins  Nitric oxide Erection require a rapid increase in blood flow. An erection occurs when the nervous system activates a rapid increase of blood flow. The vascular muscle in the spongy area inside the penis becomes engorged with blood and the outflow of blood is cut off. Numerous sexual stimuli are processed by the brain and transmitted to the penis via the nervous system. In order to increase the size of the penis, there must be an increase in blood flow to the penis and at the same time, the blood has to be prevented from leaving the penis to aid erection.

5. AUTONOMIC CONTROL In the presence of mechanical stimulation, erection is initiated by parasympathetic division of the autonomic nervous system with minimal input from the central nervous system. VOLUNTARY AND INVOLUNTARY CONTROL OF ERECTION The cerebral cortex can initiate erection in the absence of direct mechanical stimulation(in response to visual, auditory, olfactory, imagined, or tactile stimuli) acting through erectile centres in the lumbar and sacral regions of the spinal cord. The cortex may suppress erection, even in the presence of mechanical stimulation, as may other psychological, emotional and environmental factors. NOCTURNAL ERECTION The penis may erect during sleep or be erect on waking up. Such an erection is medically known as nocturnal penile tumescence. SIZE OF THE PENIS DURING ERECTION. The length of the flaccid penis does not necessarily correspond to the length of the

6. penis when it becomes erect; some smaller flaccid penises grow much longer, while some larger flaccid penises grow comparatively less. Generally, the size is fixed throughout post-pubescent life and it may be increased during surgery. DIRECTION Although many erect penises point upwards, it is common and normal for the erect penis to point nearly vertically upward or nearly vertically downwards or even horizontally straight forward, all depending on the tension of the suspensory ligament that holds it in position. APPLIED PHYSIOLOGY  Erectile dysfunction is a sexual dysfunction characterized by the inability to develop and maintain an erection.  Priapism is a medical condition which could possibly be painful, and is a prolonged erection that last for 4hours, which does not return to its flaccid state, despite the absence of both physical and psychological stimulation.  The effect of diseases and drugs can affect sexual function and desire.  If vasocongestion is not relieved in the male, particularly if very high levels of arousal were reached the male may experience testicular aching and swelling of the vas deferens.

7.  If vasocongestion does not occur in women, this leads to pelvic congestion and breast congestion with a secondary increase in size. REFERENCE