The structure of the penis is very delicate and is composed of three pillars, with two side-by-side pillars on the dorsal side called the penile corpus cavernosum; its interior is composed of small spongy cavities, hence the name penile corpus cavernosum. The small cavities are similar to the structure of small blood vessels. The two penile corpus cavernosum are wrapped by a tough white membrane, forming a functional and coordinated whole. The ventral one is called the urethral corpus cavernosum, through which the urethra passes. The penile corpus cavernosum is actually a special and delicate blood vessel. When the lumen of the corpus cavernosum of the penis is filled with blood during sexual impulses, the pressure rises, like a skin tube filled with high-pressure water, and the penis becomes thicker and harder and hard. Conversely the penis becomes thinner and softer. Penile erection involves complex psychological and physiological processes, which means it is controlled by the brain. When there is sexual desire, the nerves will release some special substances, which will act on the cavernous body of the penis, causing the cavernous cavity to expand, arterial blood will enter the cavernous body in large quantities, and the penis will become hard. At the same time, breathing and heartbeat will also increase, and the whole process is will prepare for sexual intercourse. Subsequently, with the contact and stimulation of both men and women, the excitement will further increase and the release of substances will further increase, thus ensuring that the penis can maintain a good hardness. Therefore, a man’s good erection must have the following conditions: 1, a good mental and psychological state; 2, to have good vascular function; 3, the penile corpus cavernosum itself should have normal structure and function; 4, normal nerve function. As you can see, the erection hardness of the penis is an objective indicator of good or bad overall health.