Angiography of the corpus cavernosum penis in the pony stallion during erection and quiescence.

The research explored the blood flow and vascular pattern in a pony stallion’s penis during periods of erection and inactivity, using arteriography to visualize the process.

Methodology and Experiment Setup

• The researchers focused on understanding the blood flow and vascular pattern in the penis of pony stallions. For this purpose, they used serial arteriography, a technique that provides an interior view of the blood vessels.
• The ponies were first anaesthetized using pentobarbital sodium. Then, catheters were surgically introduced into two key arteries: the internal pudendal and the obturator arteries, which are part of the penile vascular system.
• The vascular anatomy of the penis was then visualized using angiography, where an image-intensified fluoroscopy provides x-ray images of blood vessels in real-time. The visualization was recorded on film or by direct radiography.

Observations During Quiescence and Stimulation

• During periods of inactivity (quiescence), the blood flow into the part of the penis known as the corpus cavernosum penis (CCP) was limited as the blood was immediately shunted into the venous system.
• However, when stimulated mildly using an electroejaculator (a device used to obtain semen from males for breeding purposes), there was an increased filling of blood in both the CCP and the other part of the penis known as the corpus spongiosum penis. This is due to vasodilation—a widening of the blood vessels—which boosts blood flow.

Observations Related to Injected Contrast Medium

• Contrast medium, injected into the internal pudendal artery, flowed into the bulb of the penis during peak erection. This spotting technique helps to better visualize the body part in diagnostic imaging.
• However, the contrast medium injected into the obturator artery was unable to reach the crus penis—the part of the penis situated at the base during peak erection. This was due to occlusion/blockage in the deep arteries feeding the penis. The blockage occurred because of the contraction of the ischiocavernous muscles, which play a role in penile erection.
• When the contrast medium was directly injected into the CCP near the glans (the rounded part forming the end of the penis) to outline the body of the penis, researchers found no evidence of venous outlets along the body of the penis. This suggests that the blood exit paths along the body of the penis were not present or not functioning during the period of erection.