Today we see how erections in men happen. The penis has three long tubes of erectile tissue which are connected to each other by fibrous tissue. The two identical sections are called corpora cavernosa and they run parallel to each other along the sides of the penis. The third tube lies underneath the two identical section of fibrous tissue. All the three sections surround the urethra which is a tube that is responsible for transporting urine or sperm.

All three tubes look like sponges as they contain wide spaced found between loose networks of tissues. When the penis is limp or what is called flaccid by the doctors, the spaces between these tubes remain are smaller and collapsed. However when you experience an erection, blood starts to flow in between these spaces leading the penis to grow in size.

The erection and the growth of the penis occur due to psychological and physical stimulation. As the blood begins the penis there is a temporary reduction of volume and rate of blood that is leaving the penis. Hence the arteries that carry blood to the veins begin to dilate leading to funnel shaped valves that start to restrict the flow of blood.  

The pressure increases in the erectile tissue as it enlarges and the veins begin to compress against the surrounding tissue as a result of which further outflow of blood is restricted. All the three tubes do not start to swell together at this time. The lowest tube known as corpus spongiosum does not become as hard as the other two tubes. If the lowest tube became hard it would result in damage to the urethra and you would not be able to ejaculate at all. When ejaculation is over the penis size decreases and it becomes soft again. The arteries begin to relax and contract in size.          

Erection and ejaculation in teenagers happen early in just five minutes while in older men it may take some more time. The erect penis in different men may attain different angles, positions and shapes. The angle ranger from 45-90 degrees and the position may be either to the left or the right. You might be suffering from Peyronie’s disease if there is a severe curve in the penis. Treatments for such type of disorders include tablets containing Vitamin E. In severe cases a surgery may have to be performed which is also the last resort.