Nature versus nurture Certain characteristics may be innate in humans; these characteristics may be modified by the physical and social environment in which people interact.
The sexual drive affects the development of personal identity and social activities. Freud believed sexual drives are instinctive. 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: Eros the life instinct , which comprises the self-preserving and erotic instincts, and Thanatos the death instinct , which comprises instincts invoking aggression, self-destruction, and cruelty.
His instinct theory said humans are driven from birth by the desire to acquire and enhance bodily pleasures, thus supporting the nature debate. Freud redefined the term sexuality to make it cover any form of pleasure that can be derived from the human body. 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.
Later, behaviorists would apply this notion in support of the idea that the environment is where one develops one's sexual drives. A number of them, including neo-analytic theories, sociobiological theories, social learning theory , social role theory , and script theory , agree in predicting that men should be more approving of casual sex sex happening outside a stable, committed relationship such as marriage and should also be more promiscuous have a higher number of sexual partners than women.
These theories are mostly consistent with observed differences in males' and females' attitudes toward casual sex before marriage in the United States; other aspects of human sexuality, such as sexual satisfaction, incidence of oral sex , and attitudes toward homosexuality and masturbation , show little to no observed difference between males and females.
Observed gender differences regarding the number of sexual partners are modest, with males tending to have slightly more than females. They also deal with the influence of biological factors on other aspects of sexuality, such as organic and neurological responses,  heredity, hormonal issues, gender issues, and sexual dysfunction.
As adults, they have different reproductive mechanisms that enable them to perform sexual acts and to reproduce. Men and women react to sexual stimuli in a similar fashion with minor differences. Women have a monthly reproductive cycle, whereas the male sperm production cycle is more continuous.
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. Studies have shown that within lab animals, destruction of certain areas of the hypothalamus causes the elimination of sexual behavior. The pituitary gland secretes hormones that are produced in the hypothalamus and itself. The four important sexual hormones are oxytocin , prolactin , follicle-stimulating hormone , and luteinizing hormone.
Human male reproductive system Males also have both internal and external genitalia that are responsible for procreation and sexual intercourse. Production of spermatozoa sperm is also cyclic, but unlike the female ovulation cycle, the sperm production cycle is constantly producing millions of sperm daily. The male genitalia are the penis and the scrotum. The penis provides a passageway for sperm and urine. The penis's internal structures consist of the shaft , glans , and the root.
Two of these bodies lie side-by-side in the upper portion of the penis called corpora cavernosa. The third, called the corpus spongiosum , is a tube that lies centrally beneath the others and expands at the end to form the tip of the penis glans. The urethra runs through the shaft, providing an exit for sperm and urine. The root consists of the expanded ends of the cavernous bodies, which fan out to form the crura and attach to the pubic bone and the expanded end of the spongy body bulb.
The root is surrounded by two muscles; the bulbocavernosus muscle and the ischiocavernosus muscle , which aid urination and ejaculation. The penis has a foreskin that typically covers the glans; this is sometimes removed by circumcision for medical, religious or cultural reasons.
Millions of sperm are produced daily in several hundred seminiferous tubules. Cells called the Leydig cells lie between the tubules; these produce hormones called androgens; these consist of testosterone and inhibin.
The testicles are held by the spermatic cord, which is a tubelike structure containing blood vessels, nerves, the vas deferens, and a muscle that helps to raise and lower the testicles in response to temperature changes and sexual arousal, in which the testicles are drawn closer to the body. The first part of this system is the epididymis.
The testicles converge to form the seminiferous tubules , coiled tubes at the top and back of each testicle. The second part of the duct system is the vas deferens , a muscular tube that begins at the lower end of the epididymis.
The third part of the duct system is the ejaculatory ducts, which are 1-inch 2. It consists of two main zones: The Cowper's glands, or bulbourethral glands, are two pea sized structures beneath the prostate. Female anatomy and reproductive system[ edit ] External female anatomy[ edit ] External female genitals depilated. The mons veneris, also known as the Mound of Venus , is a soft layer of fatty tissue overlaying the pubic bone.
It has many nerve endings and is sensitive to stimulation. The labia majora are two elongated folds of skin extending from the mons to the perineum. Its outer surface becomes covered with hair after puberty.
In between the labia majora are the labia minora, two hairless folds of skin that meet above the clitoris to form the clitoral hood, which is highly sensitive to touch. The labia minora become engorged with blood during sexual stimulation, causing them to swell and turn red. Near the anus, the labia minora merge with the labia majora. It is the main source of orgasm in women. These opening have many nerve endings that make them sensitive to touch.
They are surrounded by a ring of sphincter muscles called the bulbocavernosus muscle. Underneath this muscle and on opposite sides of the vaginal opening are the vestibular bulbs, which help the vagina grip the penis by swelling with blood during arousal.
Within the vaginal opening is the hymen , a thin membrane that partially covers the opening in many virgins. Rupture of the hymen has been historically considered the loss of one's virginity, though by modern standards, loss of virginity is considered to be the first sexual intercourse. The hymen can be ruptured by activities other than sexual intercourse.
The urethral opening connects to the bladder with the urethra; it expels urine from the bladder. This is located below the clitoris and above the vaginal opening. Western culture is one of the few in which they are considered erotic. Breasts develop during puberty in response to an increase in estrogen. Each adult breast consists of 15 to 20 milk-producing mammary glands , irregularly shaped lobes that include alveolar glands and a lactiferous duct leading to the nipple.
The lobes are separated by dense connective tissues that support the glands and attach them to the tissues on the underlying pectoral muscles. Female reproductive system The female reproductive system. The vagina is a sheath-like canal that extends from the vulva to the cervix. It receives the penis during intercourse and serves as a depository for sperm. The vagina is located between the bladder and the rectum. The vagina is normally collapsed, but during sexual arousal it opens, lengthens, and produces lubrication to allow the insertion of the penis.
The vagina has three layered walls; it is a self-cleaning organ with natural bacteria that suppress the production of yeast.
This area may vary in size and location between women; in some it may be absent. Various researchers dispute its structure or existence, or regard it as an extension of the clitoris.
During ovulation, this thickens for implantation. If implantation does not occur, it is sloughed off during menstruation. The cervix is the narrow end of the uterus. The broad part of the uterus is the fundus. Finger-like projections at the ends of the tubes brush the ovaries and receive the ovum once it is released. The ovum then travels for three to four days to the uterus. The lining of the tube and its secretions sustain the egg and the sperm, encouraging fertilization and nourishing the ovum until it reaches the uterus.
If the ovum divides after fertilization, identical twins are produced. If separate eggs are fertilized by different sperm, the mother gives birth to non-identical or fraternal twins. The ovaries are suspended by ligaments and are the source where ova are stored and developed before ovulation. The ovaries also produce female hormones progesterone and estrogen. Within the ovaries, each ovum is surrounded by other cells and contained within a capsule called a primary follicle.
At puberty, one or more of these follicles are stimulated to mature on a monthly basis. Once matured, these are called Graafian follicles. On days one to four, menstruation and production of estrogen and progesterone decreases, and the endometrium starts thinning. The endometrium is sloughed off for the next three to six days.
Once menstruation ends, the cycle begins again with an FSH surge from the pituitary gland. Days five to thirteen are known as the pre-ovulatory stage. During this stage, the pituitary gland secretes follicle-stimulating hormone FSH. A negative feedback loop is enacted when estrogen is secreted to inhibit the release of FSH. Estrogen thickens the endometrium of the uterus. A surge of Luteinizing Hormone LH triggers ovulation.
On day 14, the LH surge causes a Graafian follicle to surface the ovary. The follicle ruptures and the ripe ovum is expelled into the abdominal cavity. The fallopian tubes pick up the ovum with the fimbria. The cervical mucus changes to aid the movement of sperm. On days 15 to 28—the post-ovulatory stage, the Graafian follicle—now called the corpus luteum —secretes estrogen. Production of progesterone increases, inhibiting LH release.
The endometrium thickens to prepare for implantation, and the ovum travels down the Fallopian tubes to the uterus. If the ovum is not fertilized and does not implant, menstruation begins.