Читать книгу Saving Your Sex Life: A Guide for Men With Prostate Cancer - John P. Mulhall - Страница 7

The major source of blood flow for erection is the deep or cavernosal artery. Given how erections work (to be discussed later), increased blood flow during erection is critical to gaining maximum rigidity and maximum sustaining capability. The cavernosal artery starts its journey in the pelvis, where it is known as the internal pudendal artery. This artery takes a circuitous course and travels underneath the ischiopubic ramus (remember, that bony structure that we sit on while on a bicycle seat). It travels in a special canal along with the dorsal (sensory) nerves. The right artery travels on the right side, the left artery travels on the left, and they pass about one-third of the way into the erection chamber and give off numerous branches to supply blood to the lacunar spaces inside the erection tissue. This artery at rest is approximately 0.5 mm in diameter and during erection dilates (expands) to approximately 1 to 1.2 mm in diameter. When you appreciate that the coronary arteries are 1.5 to 3 mm in diameter, you can appreciate why we now believe that there is a link between penile blood flow problems and hidden or future coronary artery disease. There is accumulating evidence to suggest that men who have erectile problems are more likely currently or in the future to develop blockage of their heart arteries, which, of course, is a risk factor for heart attack.

Figure 3 • High power view of erectile tissue. The lacunar spaces are lined by endothelium beneath which is smooth muscle. In the space between the lacunar spaces run the nerves.

To make matters more complicated, there are a series of arteries that travel very closely to the prostate, known as accessory pudendal arteries. It is important to understand that the prostate sits on a layer of muscle known as the urogenital diaphragm known officially as the levator ani muscles but more commonly referred to as the pelvic floor. The two erection arteries, the cavernosal arteries, sit beneath this and cannot be injured at the time of prostatectomy. However, with radiation, these arteries fall into the field of radiation exposure. The accessory pudendal arteries, on the other hand, sit above the pelvic floor muscles and travel very close to the prostate. They are also potentially threatened and injured at the time of prostatectomy and during radiation therapy. How common these arteries are is variable. It is generally believed that somewhere in the range of one in four men have an accessory pudendal artery, and in a majority of these men, these arteries are contributors to erection. Indeed, in some, these blood vessels are the major source of arterial blood flowing into the penis for the purpose of erection. Thus, you can see that, if they are injured at the time of radical prostatectomy or exposed to radiation, this may, in fact, impair erection function recovery after both of these treatments.

The anatomy of the venous drainage from the penis is complicated and highly variable. There are numerous veins that leave the penis traveling on the top and bottom surfaces. These veins carry blood from exits the lacunar (erection) spaces through the emissary veins. These veins are tiny veins that travel from the erection tissue through the tunica albuginea into the subcutaneous veins that drain blood back into the general circulation.