An erection occurs with an increase in blood flow to the penis: the net of empty veins running in the cavernous and spongy bodies is filled, the penis thickens and lengthens until it is filled
How does an erection
An erection occurs with an increase in blood flow to the penis: the net of empty veins running in the cavernous and spongy bodies is filled, the penis thickens and lengthens until it is filled