Rekha told her friend Babita that even after four years of marriage she is not able to bear a child and sarcastic remarks of her in-laws make her depressed. Rekha told Babita that she and her husband should get examined by a doctor. After examination, doctor found no abnormalities in Rekha and his husband except low sperm count of her husband. Rekha told her friend that her husband takes alcohol, drugs and smoke daily. Her husband has some defects in the erection of penis.
What is the use of erection of the penis?