* Erection and [[Reproductive_Behaviour_-_Pre-copulatory_Behaviour_-_Anatomy_%26_Physiology#Penile_Protrusion|protrusion]] involve straightening of the penis to eliminate the '''sigmoid flexure'''. | * Erection and [[Reproductive_Behaviour_-_Pre-copulatory_Behaviour_-_Anatomy_%26_Physiology#Penile_Protrusion|protrusion]] involve straightening of the penis to eliminate the '''sigmoid flexure'''. |