&lt;b&gt;SCANNING ELECTRON MICROSCOPE OBSERVATION OF PENILE VASCULAR CASTS IN THE DOG: AN INQUIRY INTO THE POSSIBLE MECHANISM OF ERECTION BASED ON THE &lt;/b&gt;&lt;b&gt;FINDINGS &lt;/b&gt;

The present study was performed in dogs to determine the site preventing the backflow from the corpus cavernosum to the arterial vessels when the corporeal pressure rises more than the systemic pressure (rigid phase). We confirmed a great gradient (325 ± 81 mm Hg, mean ± SD) between the corporeal pressure and the deep arterial pressure; the latter was measured at the distal point over the tunica albuginea, namely within the corpus cavernosum. This finding indicated that the mechanism preventing the arterial backflow existed within the corpus cavernosum. This assumption was supported by our light-microscopic findings that the helicine arteries were closed in the rigid phase, whereas they were dilated when the corporeal pressure was lower than the systemic pressure (tumescence/full erection phase). The results suggest that the helicine arteries play an essential role in the prevention of the arterial backflow in the rigid phase.

Section: Discussionmentioning

confidence: 99%

Mechanism Preventing Backf low from the Canine Corpora cavernosa to Arteries in the Rigid Phase of Penile Erection

Tamaki¹

1992

“…On the other hand, Stieve [9] claimed that such a compression was an artificial and distorted figure. Conti [10] and Goldstein et al [11] attributed the restriction of the venous outflow to the contraction of polsters in the veins of the penis, although we dispute the existence of venous polsters at least in the dog penis [4,7], In a previous study [4], we produced vascular corro sion casts of dog CCP in flaccid, erect and rigid states, and revealed under the scanning electron microscope that the venous occlusion during the erect and rigid states occurred in both the postcavemous venules and the penetrating veins. We further determined that the deep artery passing through the tunica albuginea was occluded during the rigid state to prevent any backflow of blood from the cavernous sinuses [4], In the present study, we carried out light-microscopic observation of dog penile blood vessels in order to clarify the mecha nism of such vascular occlusions.…”

Section: Discussionmentioning

confidence: 92%

“…(1) Vasoactive intestinal polypeptide involved in vasodi latation has been shown to be abundantly present in the cavernous tissues of the penis and to be localized in neu ral elements [12]. Vasoactive intestinal polypeptide-con taining nerves were densely distributed in smooth mus cles dispersed in cavernous trabeculae as well as in those of helicine arteries [7,12]. Papaverine, a relaxant of smooth muscles, induces erection; it has also been dem onstrated to cause restricted venous outflow from cav ernous sinuses [3,4], These data suggest that the relax ation of trabecular smooth muscles may be important for erection, probably as the cause of the restriction of venous outflow as well as the vasodilatation of the heli cine arteries, which gives rapid inflow with high pressure to the cavernous sinuses.…”

Section: Discussionmentioning

confidence: 99%

“…the penis was removed and immersed in the same fixative for about 24 h. The crus penis and the junctional region between the crus and the shaft of the penis were dissected out, since our previous studies showed that the penile deep artery and draining veins passed through the tunica albuginea in this region [4,7], Specimens were dehydrated in an ascending series of ethanol and embedded in paraffin. Paraffin sec tions were cut serially at 10 pm thickness in two different planes (longitudinal and transverse planes with regard to the vessels) and stained with hematoxylin and eosin or Masson-Goldner's tri chrome.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Morphological Changes in Penile Vessels during Erection: The Mechanism of Obstruction of Arteries and Veins at the Tunica albuginea in Dog Corpora cavernosa

Hanyu

1988

Self Cite

The present study deals with morphological changes during erection both in the penile deep artery supplying the corpus cavernosum and in veins draining it. These vessels were shown to maintain wide lumina in the flaccid state. In the erect state induced by injection of papaverine, the postcavernous venules were compressed between the cavernous sinuses and the tunica albuginea. Simultaneously, the penile deep artery and the penetrating vein were strangulated by stretched collagen bundles in the inner layer of the tunica albuginea. Quite noteworthy was a wedge-shaped connective tissue mass between the penetrating vein and the postcavernous venules converging to it, and plugged, in the erect state, towards the penetrating vein to effectively stem the venous outflow. When the rigid state was induced by papaverine injection and following intracavernous injection of a fixative by high pressure, the arterial and venous obliteration mentioned above was so intense that the vessels almost lost their lumina, resulting in the cavernous sinuses becoming isolated from the systemic circulation.

“…9] or perforating veins [10] and postcavernous ven ules [5,8,9] which connect the cavernous sinuses with the penetrating vein showed a wide lumen in the flaccid state ( fig. 4a, 5a).…”

Section: Histological Examinationmentioning

confidence: 99%

Increase in Venous Outflow From the Corpora cavernosa during Mild Erection in Dogs

Hanyu¹,

Iwanaga

Tamaki³

et al. 1992

Self Cite

The venous outlet of the corpus cavernosum is generally believed to be obstructed during erection. Some researchers, however, have demonstrated an increased venous outflow during erection. To elucidate this discrepancy, we carried out a pressure-flow study using a perfusion model of the penile deep artery in dogs. Various states of the corpus cavernosum, which were different in cavernous pressure, were induced by a delicate control of electrostimulation to the cavernous nerve. Inflow rate into the corpus cavernosum, inflow resistance and outflow resistance were simultaneously evaluated. The inflow rate in mild erection was higher than in the flaccid state, and the outflow rate was estimated to be also higher than in the flaccid state. A probable reason for the increased outflow rate was that the arterial resistance decreased remarkably, while the venous resistance only slightly increased. In full erection, both the inflow and outflow rates were lower than in the flaccid state because of a great venous resistance. Histological observation of the canine penis indicated that compression of draining veins passing through the tunica albuginea was weak in mild erection, while intense in full erection. It was proposed that in mild erection, the effect of venous occlusion was slight though that of arterial dilation was noticeable, resulting in an increase in the venous outflow.