Male Sexual Health: Erections
Anatomy, Evolutionary Biology, Puberty in Teen Boys, Arousal

Male Physiology & Sexual Function - The Penis, Erections, Normal Size, Disorders

A comprehensive essay on male sexual and reproductive functioning. Topics include: normal size of the male sexual organs, aging and sexuality, role of neurochemicals in each stage of the sexual cycle, erections, influence of psychological factors, drugs and disease on all aspects of sexual functioning and the investigation and treatment of male sexual disorders.

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From the website: Penis Diagram and Mechanism of Erection

Figure 1. Anatomy and mechanism of penile erection. The cavernous nerves (autonomic), which travel postarterolaterally to the prostate, enter the corpora cavernosa and corpus spongiosum to regulate penile blood flow during erection and detumescence. The dorsal nerves (somatic), which are branches of the pudendal nerves, are primarily responsible for penile sensation. The mechanisms of erection and flaccidity are shown in the upper and lower insets, respectively. During erection, relaxation of the trabecular smooth muscle and vasodilatation of the arterioles results in a severalfold increase in blood flow, which expands the sinusoidal spaces to lengthen and enlarge the penis. The expansion of the sinusoids compresses the subtunical venular plexus against the tunica albuginea. In addition, stretching of the tunica compresses the emissary veins, thus reducing the outflow of blood to a minimum. In the flaccid state, inflow through the constricted and tortuous helicine arteries is minimal, and there is free outflow via the subtunical venular plexus. [Reproduced from T. F. Lue: N Engl J Med 342:1802–1813, 2000 (2 ). © Massachusetts Medical Society. All rights reserved.]

Male Sexuality - Arousal, Erection, Penis Size & Orgasm

From the essay: 'An erection of the penis occurs as the spongy tissues of the penis are engorged with blood. There is one large primary artery responsible for blood flow into the penis, but several veins that drain the penis of blood. When an erection is not happening, the inflow of blood and the outflow is maintained in balance and the penis remains flaccid. During erection, blood flows into the penis and holes in the spongy tissue in the penis fill with blood. At the same time, flaps in the veins leading out of the penis enlarge, cutting off the drainage. As a result, the penis fills with blood. As more and more blood flows in than out, the penis enlarges and becomes harder. Finally, veins in the penis are compressed from the increasing pressure from the erection itself. Heart rate and blood pressure also increase, the pressure of blood into the penis increases, keeping the penis hard.
The size of the erection may be relatively unrelated to the size of the non-erect penis. Typically, those with smaller penises tend to enlarge to a greater degree when erect, so the differences in the size of the erect penis may not be that great. According to the book Man's Body, the average flaccid penis is about 3 3/4 inches long with most falling between 3 1/4 and 4 1/4 inches, though a few are outside this range. The average erect penis is 6 1/4 inches, with most between 5 and 7 inches.'

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Evolution, Human Reproduction & Fertilization: Sperm Competition & the Penis

A very interesting essay from the journal of Evolutionary Psychology on sperm competition and its role in shaping the human penis, (size, length, width, forceful ejaculation), evolutionary strategies for successful fertilization i.e. semen displacement and coagulation. On sexual intercourse and evolutionary benefits of deep penis thrusting, function of the foreskin and effects of circumcision, premature ejaculation, female reproductive strategies i.e. copulation with multiple partners, human sexual behaviour and wife rape (males having sex with their partner if suspecting them of infidelity).

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Analyse any human emotion, no matter how far it may be removed from the sphere of sex, and you are sure to discover somewhere the primal impulse, to which life owes its perpetuation. ... The primitive stages can always be re-established; the primitive mind is, in the fullest meaning of the word, imperishable. ... Mans most disagreeable habits and idiosyncrasies, his deceit, his cowardice, his lack of reverence, are engendered by his incomplete adjustment to a complicated civilisation. It is the result of the conflict between our instincts and our culture. (Sigmund Freud)

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Male Sexual Health: Penis Erections. Biology, Puberty in Teen Boys, Sexual Arousal, Erotic Art, Pictures

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