Sexual intercourse is a biological reproductive device.
Sensual pleasure motivates humans to have sex.
Certain changes occur in both genders before, during and after sexual intercourse. These include changes in the genital organs and other parts of the body. This makes the penis stiff and rigid, thereby helping it to standout of the body. The scrotal sac is raised slightly due to its muscular contraction, thereby drawing the testes upwards. The walls also turn purple.