The hymen can be ruptured by activities other than sexual intercourse. He also proposed the concepts of psychosexual development and the Oedipus complex , among other theories. The pelvic muscle near the vagina, the anal sphincter, and the uterus contract. It consists of two main zones: His developmentalist perspective was governed by inner forces, especially biological drives and maturation, and his view that humans are biologically inclined to seek sexual gratification demonstrates the nature side of the debate. Freud redefined the term sexuality to make it cover any form of pleasure that can be derived from the human body. The urethra runs through the shaft, providing an exit for sperm and urine. They are surrounded by a ring of sphincter muscles called the bulbocavernosus muscle. Arousal disorder means lack of vaginal lubrication. This is a small area at the base of the brain consisting of several groups of nerve cell bodies that receives input from the limbic system. He was a firm supporter of the nature argument; he said there are a large number of instincts but they are reduced into two broad groups: During the orgasm stage the heart rate, blood pressure, muscle tension, and breathing rates peak. Age does not necessarily change the need or desire to be sexually expressive or active. The labia minora become engorged with blood during sexual stimulation, causing them to swell and turn red. Theories have linked many factors, including genetic, anatomical, birth order, and hormones in the prenatal environment, to homosexuality.