Conti's hypothesis of human penile erection is well known, and penile hemodynamics is explicated by the fine penile anatomy observed by Conti.
Recently it is suggested that there may be some inosistencies in his hypothesis. For the purpose of investigating human penile erection, penile micro-circulation was observed by the Yagi's polarographic method.
As an index of the tissue blood flow changes, measurements of the tissue oxygen tension were made polarographically in the penile skin, the corpus cavernosum and the thigh skin of 16 males aged 20-26 years.
The oxygen cathodes of an enameled copper wire, 300μ in diameter, were implanted in those tissues, and the tissue oxygen tensions were measured as the electric voltage instead of the electric currents flowing through the oxygen cathodes, and the polarographic amplitudes were expressed as the changes in the electric voltage.
At first, the levels of each tissue oxygen tension were measured when the penis was flaccid. The changes in response to inhalation of high oxygen gas mixture were also measured.
Furthermore, penile erection was induced by visual and auditory sexual stimulation.
During all processes of the erection, the changes of the tissue oxygen tension were measured.
The results were as follows;
1. In the flaccid penis, the tissue oxygen tension of the corpus cavernosum was 69±30μv (mean±S. D.) and no changes could be observed in response to the inhalation of high oxygen gas mixture.
2. In the flaccid penis, the tissue oxygen tension of the penile skin and thigh skin were 187±91μv (mean±S. D.) and 210±106μv (mean±S. D.) respectively. In response to inhalation of high oxygen gas mixture those tensions increased up to 410±135μv (mean±S. D.) and 405±206μv (mean±S. D.), respectively.
3. At the onset of erection, the tissue oxygen tension of the corpus cavernosum increased up to 494±218μv (mean±S. D.) and this level is about 7 times as high as that of flaccid penis.
4. When the erection was secured, the tissue oxygen tension of the corpus cavernosum gradulally decreased to 253±106μv (mean S. D.) which was still significantly higher than the flaccid level.
5. In the process of detumesence, the tissue oxygen tension of the corpus cavernosum showed a transient increase to 401±237μv (mean±S. D.). After a while it dropped to the flaccid level.
6. The tissue oxygen tension of the penile skin decreased to 145±105μv (mean±S. D.) from 187±91μv (mean±S. D.) of the flaccid level, and was kept at this level druing all processes of erection. There was no change of the tissue oxygen tension of the thigh and remained at 210±106μv (mean±S. D.) of the flaccid level.
On the basis of these results, the mechanism of the human penile erection was deduced. The increase of arterial inflow to the corpus cavernosum cause the increase in penile volume during the onset of erection. Even though a steady-state of erection is reached, the importance of a continuous high-volume flow for erection has been demonstrated. However, once erection is secured, it can be maintained by a somewhat slower flow. This suggests that the resistance was passively increased following the establishment of erection.
On the other hand, a decrease in blood flow occurs in the penile skin during erection.
The subsidence of penile erection may be caused not only by a decrease inflow to the corpus cavernosum but also by it's contraction.
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