Why is a man's scrotum black and wrinkled?

The scrotum is like a thin-walled, tough leather pocket that grows between the base of the penis and the perineum, where it hangs when a person stands, connecting to the pubis penis pump , penis skin deep anal dildo , medial thigh skin and perineal skin, respectively. From the outside, there is a vertical scrotal suture on its midline, which is the mark left by embryonic development. The skin of the scrotum is soft and weak, smooth and elastic, with thin and curly pubic hair. Under the skin rabbit vibrator , there is only a meat membrane composed mainly of smooth muscle, which contains dense connective tissue and a lot of elastic fibers. The anterior and posterior walls of the fleshy membrane extend deeply in the midline and connect each other to form a diaphragm. The scrotum is divided into two small pockets containing the left and right testes and epididymis respectively. There are abundant blood vessels in the meat membrane. Under the fleshy membrane, there are several layers of fascia and clonorchitis, which are mainly composed of abdominal muscle aponeurosis and muscle fibers. There is also a spermatic cord in the scrotum, which is a round cord composed of vas deferens, testicular artery, vine venous plexus, many small blood vessels, nerve plexus, lymphatic vessels and capsule. The support and coating of the scrotum, the suspension of the spermatic cord and the levator muscle all play a mechanical protective role on the testis, which can cushion the vibration of the testis during walking and exercise, and has certain significance in preventing trauma. Scrotal skin is very sensitive to external temperature, there is no subcutaneous fat and rich sweat glands, which helps to dissipate heat. When swimming, the water temperature is much lower than the body temperature, stimulating the smooth muscle of the meat membrane and the clitoris muscle to contract, raising the position of the testis, the skin of the scrotum will contract into dense wrinkles and shrink back to the perineum to prevent heat dissipation and help to keep warm. The same phenomenon can happen when the weather is cold. On the contrary, when the external temperature increases, the smooth muscle and the clitoris muscle relax, the testis drops, leaves the body rose toy , the skin of the scrotum is relaxed, and increases the heat dissipation area, which is conducive to local heat dissipation. In addition, the arteries in the spermatic cord are wound around the parallel venous plexus, and the blood flows in the opposite direction only through the thin walls of the two vascular systems, forming a countercurrent exchange system. The venous blood constantly takes away the heat from the arterial blood in the abdominal cavity. As a result, the blood temperature of the testicular artery is 5.2 degrees lower than that of the abdominal aorta. The scrotum regulates the temperature in the scrotum and testis through these mechanisms. You must not underestimate this ability of the scrotum, it is too important for human reproduction. Because the temperature has a great influence on the spermatogenic process of the testis. The temperature in the scrotum is about 2 degrees lower than that in the body, which is the most suitable temperature for spermatogenesis. If the temperature is too high, the spermatogenesis will appear obstacles, or even stop completely, and at the same time, the secretion of testosterone will also be reduced. It is worth noting that the failure of any of the above links will affect the regulation of scrotal temperature and cause infertility. Such as too much fat in the scrotum, testicles do not fall into the scrotum, varicose veins slow down the speed of blood flow and can not take away the heat in time, tight pants affect air circulation and press the testicles tightly to the perineum, all of which are introduced in this book. As for the black skin of the scrotum, it is affected by sex hormones. Originally, a person's skin color depends on a variety of pigments, especially the amount of melanin, the thickness of the skin and the contraction or relaxation of blood vessels. The important factor that affects skin melanosis is sex hormone. Sexual organs and other parts of the high concentration of sex hormones, long-term hormone stimulation results in a large number of melanin calm and the skin becomes very dark, especially after wrinkling and thickening is more obvious. By the same token, you may have noticed that the nipples of adult men and the surrounding areola are quite dark. And the little boy's sex hormone level is very low, so the skin color does not change much, the scrotum and the surrounding skin color is similar, after entering puberty, there will be this change of pigmentation.
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