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Originally posted by sunshinekid403 Now while the penis is not a muscle per se, it is covered with a layer of smooth muscle (our doctors on the board can argue all they want, I have pictures in my books).
It sure has smooth muscle in it somewhere. What do your books show?
Lacunar space (Space of Smith)
Surrounds tunica albuginea
Intralacunar smooth muscle found within space
http://www.quit … penis_facts.htm
This damage to the blood vessels leads to reduced levels of oxygen which results in increased collagen formation. This affects the elasticity in the penis by upsetting the balance between collagen and elastin in the penis. In the penis, the ideal ratio between collagen and smooth muscle (which contains elastin) is 48% (collagen) : 52% (smooth muscle which contains elastin). When this ratio is upset by an increased proportion of collagen (i.e. a relative decrease in the proportion of elastin) the penis becomes less elastic.
http://www.vaso … om/vasomax.html
In men with normal erectile function, the penis is composed of 42% to 53% smooth muscle. As men age, blood flow to the penis may decline causing the normal structure of the penis to change; smooth muscle may be replaced by fibrous tissue that cannot expand sufficiently to initiate and maintain an erection. Symptoms of erectile dysfunction typcially begin when smooth muscle in the penis falls below 42%.
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Penis
The penis contains three cylinders of erectile tissue; the corpora cavernosa which are two cylinders lying side by side on the dorsal side and corpus spongiosum, a single cylinder on the ventral side which contains the urethra (Penis 1). Each cavernous body is surrounded by connective tissue; all three are surrounded by elastic loose connective tissue and a layer of thin skin. The erectile tissue consists of a framework of irregular trabeculae containing collagen, elastin, and smooth muscle, covered by endothelium. This arrangement produces a number of irregular spaces or blood sinuses, which become engorged with blood to produce the erection (Penis 2).
http://www.edhe alth.org/what_i … ed/erection.htm
[good site on anatomy and erection]
The corpora cavernosa can be thought of as sponges made of smooth muscle fibres. When the penis is soft, the muscle fibres are contracted and only a small amount of blood can be contained within the penis. During erection, the signals passing along the cavernous nerves cause the smooth muscle to relax, allowing the "sponges" to expand, filling with blood. The pressure within the corpora cavernosa increases and the penis becomes rigid. See Figure 2
1) Nitrergic-noradrenergic interaction:
Penile erection is regulated by two opposing systems: noradrenergic (anti-erectile) and nitrergic (pro-erectile) neurotransmission. Noradrenaline released from sympathetic nerves causes contraction of the blood vessels and smooth muscle of the penile corpus cavernosum, thus leading to detumescence of the penis.
http://www.vmmc … ogy/sec4058.htm
Veno-Occlusive Dysfunction
The erectile cylinders within the male penis contain arteries, capillary beds, smooth muscle, and venules. In the unexcited state small amounts of blood enter the penis from the penile arteries. This blood goes through the sinusoidal spaces, and enters the venules which come together to form veins that carry the blood out of the penis and back to the heart.
In the excited state, the penile arteries open and a much greater volume of blood enters the erection cylinders. The smooth muscle within the cylinders relaxes, so that the arterial blood enters the capillary spaces and the small venules are obstructed. As more and more blood enters the cylinders, the pressure within the cylinders rises and the patient achieves a rigid erection.
In a young, healthy male, the amount of blood required to maintain this erection is as low as 2cc per minute. As patients age, this smooth muscle within the penile cylinders becomes less able to relax and occlude the venules. This allows some of the blood which enters the penis to drain out through the veins causing a venous leak. At some point, this venous leak becomes larger than the amount of blood entering the penis and the patient becomes unable to obtain/or maintain the erection. Veno-occlusive disease is the #1 cause of sexual dysfunction worldwide.