Lecture Notes

The external male sexual structures are the penis and the scrotum. The penis is the organ through which both sperm and urine pass. It is attached to the male perineum, the diamond-shaped region extending from the base of the scrotum to the anus. The penis consists of three main sections: the root, the shaft, and the head. The root attaches the penis within the pelvic cavity. The body of the penis, or the shaft, hangs free. At the end of the shaft is the head of the penis, which is also referred to as the glans penis. At the tip of the glans is the urethral orifice. The urethral orifice is for both semen ejaculation or urine excretion. On the underside of the penis is a triangular area of sensitive skin called the frenulum, which attaches the glans to the foreskin. The shaft of the penis contains three parallel columns of erectile tissue. The two that extend the front surface are known as the corpora cavernosa. This is the same type of erectile tissue within the crura of the clitoris. The third column, which runs beneath the corpora cavernosa, is called the corpora spongiosum and also forms the glans. Inside the three chambers are a large number of blood vessels through which blood freely circulates when the penis is relaxed. During sexual arousal these vessels fill with blood and expand, which causes the penis to become erect.