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PHS 204- REPRODUCTIVE PHYSIOLOGY NAME > Kalu anita MATRIC NO > 13/MHS01/063 DEPARTMENT> MEDICINE & SURGERY Assignment given by> Akintayo Mr. Christopher Submission date> 11/6/2015, via ABUAD LMS platform. Question> Discuss on the Physiologies of Coitus and Erection. THE PHYSIOLOGY OF COITUS AND ERECTION THE PHYSIOLOGY OF COITUS INTRODUCTION DEFINITION Coitus is the sexual union between the male and female genitals. It is usually accompanied by rhythmic movements and orgasms. During coitus, the male genitalia (penis) enters the vagina of the female and begins the process of rhythmic movements, in order to stimulate the female and to cause proper sexual arousal in the female; while in the process, the male equally becomes increasingly aroused till the release of semen by the penis deep inside the vagina via ejaculation. This point coincides with sexual climax. The semen of the male contains the male gamete- spermatozoa, which then swims along the female reproductive tract to fertilize the female ovum at the fallopian tube. In both male and female, the following four phases occur during coitus: I. II. III. IV. Excitement/Arousal phase. Plateau phase. Orgasm. Resolution. EXCITEMENT/AROUSAL PHASE i. In Male During excitement in males, the following 3 phases occur in succession: Erection of the penis: o This is caused by parasympathetic nerve impulses through the pelvic nerves to the penis, where the neurotransmitters: Acetylcholine, Nitric oxideand Vasoactive IntestinalPolypeptide (VIP)are released. This causes blood vessel dilation and enlargement of the penis. Thickening of the scrotal sac. Rising of the testes ii. In Females The sequential order of the processes involved in the arousal phase of Coitus in females is: The nipples become erect. The breasts swell. The release of vaginal fluid. Erection of the clitoris: This too, is by the parasympathetic nerves from the sacral plexus to the external genitalia; the arteries of the erectile tissue are dilated, due to the release of Acetylcholine, Nitric Oxide, or VIP at the nerve endings. These processes allow for the straightening of the Introitus around the penis during coitus. PLATEAU PHASE i. In Males During the Plateau phase in males, the following occur: Appearance of sex flushes Swelling of the Glans Penis. Swelling of the testes. ii. In Females The Plateau phase of coitus in females is characterized by the following: o o o o Sex flushes (as in males). Withdrawal of the clitoris. Enlargement of the Labia Majora. Rising of the Uterus. ORGASM This phase is also called Climax. It is the ultimate stage of Coitus. The objective of this phase in both sexes is to provide maximum sexual satisfaction and to terminate sexual arousal. However, this phase differs in its physiological processes in both males and females. i. InMales Here, this phase is coincident with the function of semen. This is mediated by the SuperiorHypogastric Plexuses, and it is by sympathetic stimulation. In paraplegics, ejaculation can be induced by a pacemaker, which acts to stimulate the Superior Hypogastric Plexuses. ii. In Females The muscle of sexual climax in females is called the Bulbospongiosus. It is capable of rhythmic contractions and it too is controlled by the Superior Hypogastric plexus. Although this muscle is skeletal, its nerve supply is Autonomic. Female climaxes are associated with Clonic-tonic Contractions, which are certain forms of spasmodic contractions. The motor function of sexual climax in which the Bulbospongiosus goes into rhythmic contractions, is due to the Inferior Hypogastric Plexus. The following events occur during female climaxes: Rhythmic vaginal contractions. Rhythmic Bulbospongiosus contractions. Contraction of the uterus. Spastic contraction of the pelvic floor musculature. Heavy breathing. RESOLUTION PHASE This is the phase of coitus that occurs after sexual climax has been attained. Generally, this phase functions to return the male and female genitalia to the normal physiological states. The events of this phase differ for both sexes. i. In Males Resolution phase is characterized by: Loss of erection Blood flow to the penis is returned to the normal. There is a loss of the erectile position of the penis and eventual relaxation of the penis. Restoration of prepuce. This is however common to uncircumcised males. ii. In Females The resolution phase in females is accompanied by: Return of the nipples to normal. I.e., the nipples begin to lose their erectile position. The clitoris becomes erect again. Perspiration. THE PHYSIOLOGY OF ERECTION INTRODUCTION DEFINITION Erection is a state marked by a firm, turgid and erect position of the previously-flaccid genitialia (such as the penis), which contains cavernous tissue, as a result of dilation of such tissue with blood. It is associated with sexual arousal, emanating from sexually-related psychic and/or physical stimuli. Erection is a hydraulic event, regulated by hormones and nerves, which allow increased blood flow into and storage of blood within the erectile bodies, leading to an increase in pressure and the development of rigidity (hardness). Penile erection is triggered by either one of the following two main mechanisms: I. II. By direct stimulation of the genitalia. By stimulations coming from the brain (fantasy, smell, etc.) Following stimulations, the following events occur: Chemicals are released in the brain, which cause signals to pass down the spinal cord and outward through special nerves called Nervi erigentes into the penis. The release of Nitric oxide by the Nervi erigentes, which causes thesmooth muscles to in the penis to relax and then blood rushes into the erectile bodies to cause erection. o By this way, the erection mechanism can be likened to a firm tire; a firm tire is dependent upon a hose that delivers a continuous supply of adequate amounts of air in a speedy fashion and a valve mechanism that holds the air in place. In the penis, the hose is represented by the erection arteries which rapidly carry blood into the erectile bodies. The valve mechanism, while complicated in its structure, ensures that blood is trapped inside the erectile bodies until ejaculation occurs or till sexual stimulus has passed. However, there are certain conditions that can inhibit the erection mechanisms. Some of such include: Anxiety or fear, which prevent brain signals from reaching the level required to induce erection Medical conditions such as diabetes,heart and vascular diseases, neurological disorders, hormonal imbalances, chronic diseases such as kidney or liver failure; alcoholism and drug abuse, which can block the erection arteries or cause scarring of the spongy erection tissues and prevent proper blood flow or trapping of blood and therefore, limit erection. APPLIED PHYSIOLOGY 1. ERECTILE DYSFUNCTION This is a persistent failure to generate sufficient penile body pressure to achieve vaginal penetration and the inability to maintain this degree of penile rigidity until ejaculation. Penile diseases such as congenital malformation, peyronie’s disease, priapism, phimosis and rarely cold abscess may interfere with erectile function. There are two classification that have been proposed for erectile dysfunction; viz Psychogenic erectile dysfunction Neurogenic erectile dysfunction PSYCHOGENIC ERECTILE DYSFUNCTION This is the most common type. It is caused as a result of inhibitory messages from the spinal erection center sent by the brain as an exaggeration of the normal suprasacral inhibition or excessive sympathetic outflow which may increase penile smooth muscle tone to prevent the relaxation necessary for erection. NEUROGENIC ERECTILE DYSFUNCTION An erection is a neurovascular event, any disease or dysfunction affecting the brain, spinal cord, cavernous and pudendal nerves can induce dysfunction of penile erection. 2. EJACULATION DISORDERS There exists a spectrum of disorders of ejaculation ranging from mild premature to severely retarded or absent ejaculation. Premature ejaculation is the most common male sexual dysfunction. Psychogenic post ejaculatory pain syndrome (PEPs) is a rare sexual disorder of male dyspareunia that is described as a persistent and recurrent pain in the genital organs during ejaculation or immediately afterward. It may result from epididymal congestion after vasectomy or from duct obstruction or infection, testicular torsion, mass lesion or prostatitis. REFERENCES http://www.webmd.com/sexual-conditions/mens-sexual-problems https://www.cornellurology.com/clinical-conditons/erectiledysfunction/causes-of-erectile-dysfunction/ https://www.cornellurology.com/clinical-conditions/erectiledysfunction/how-erections-work/