Sorry I was just being too sinple in lay terms. You are right that tere are no main muscle being present in the penis as in your arm or leg but I was thinking and refering the the muscles that conrtol the penis. but to help people understand this issue please read on.
A man gets an erection when the penis enlarges and stiffens.
It is a complex process that happens as a result of changes within the muscles, nerves and blood vessels of the penis.
The regulation of blood flow into and out of the penis is what makes an erection possible.
1.Touch, sights, sounds, erotic memories, fantasies etc, cause sexual excitement.
2.These stimuli increase signal output from a part of the brain called the para-ventricular nucleus.
3.These signals then pass through special autonomic nerves in the spinal cord, the pelvic nerves and the cavernous nerves that run along the prostate gland to reach the corpora cavernosa and the arteries that supply them with blood.
4.In response to these signals, the muscle fibres in the corpora relax, allowing blood to fill the spaces between them.
5.Muscle fibres in the arteries that supply the penis also relax, and there is an eight-fold increase in blood flow to the penis. The increased blood flow expands the corpora, then stretches the surrounding sheath (the tunica).
6.As the tunica stretches, it blocks off the veins that take blood away from the corpora cavernosa. This traps blood within the penis, the pressure becomes very high and the penis becomes erect.
7.During an erection pressure in the penis is at least twice the pressure of blood in the main circulation. This is possible because the muscles of the pelvic floor contract around the base of the corpora cavernosa.
8.At orgasm, the signalling from the brain changes dramatically. There is a sudden increase in noradrenaline production from nerves in the genitalia. This seems to both trigger orgasm and contract the muscle fibres in the corpora cavernosa and their supplying arteries.
9.The pressure within the corpora drops, which also relaxes the tunica and so allows blood to flow out of the penis.
It is a complicated issue and as you can see and although no main muscles are present it is the muscles in the pelvic floor that contract around the Corpora Cavernosa which provides the increase in blood pressure in the penis to allow an erection. If this muscle atropys then the presure in the penis does not reach as high of presure as the muscles in the Corpora Cavernosa relax and thus the issue of size appears to be reduced. I also believe that the fibers in the tissue of the penis shrink as with a overweight person the skin around the middle shrinks as long as the fibers were not overly streached from someone that was morbidly obease. This is obviously reversed once the penis functions normally.
Sorry for such a long post but I am just trying to help.
Have a great andsafe new years all.
Danielle
If you lost a quarter inch in 2 or 3 months, assuming a linear reaction that should just about get you there.