BLOOD AND NERVE SUPPLY
1. What is the function of the pampiniform plexus?
2. Where does stimulation occur to provide for the afferent side of the reflexes associated with erection and ejaculation?
Blood to the testicles is supplied by the testicular arteries.
The testicular veins parallel the testicular arteries. Both artery and vein are enclosed within the spermatic cord (see Figure 14-6). A short distance above the testicle, the testicular vein is convoluted (the pampiniform plexus) and is in close association with the convoluted part of the testicular artery (Figure 14-14). Their closeness, and because they are convoluted and are therefore longer, is the means whereby blood entering the testis is cooled by the venous blood leaving the testis. The arteries and veins are also close to the surface of the testes, whereby direct loss of heat from the testes is favored. Spermatogenesis requires a cooler temperature than normal body temperature. Arterial blood to the penis provides for filling of the cavernous tissue and provides nutrition to the tissues. In most species the exclusive supply is the artery of the penis, a terminal branch of the internal pudendal arteries. The blood supply to the penis of the horse is slightly different from that of other species and is more extensive.
■ FIGURE 14-14 Lateral view of the stallion testis with emphasis on the pampiniform plexus. The pampiniform plexus is illustrated by the intertwining of the testicular artery and vein. This allows for the cooler venous blood to cool the warmer arterial blood going to the testis. Also, closeness of testicular arteries and veins to the testicular surface favors direct loss of heat from the testes.
In addition to autonomic nerve fibers to the testes, penis, and accessory sex glands, the penis is supplied by a spinal nerve, the pudendal nerve. Terminations of the pudendal nerve are located in the glans penis. Sensory stimulation of the glans provides the afferent side for reflexes associated with erection and ejaculation. Reflex centers for erection and ejaculation are located in the lumbar region of the spinal cord.
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