Everybody says that men have only one thing on their minds. And
ever since Freud, every thing from cigarettes to skyscrapers has been
described as phallic symbols. Men think of the world in terms of the 'haves' and the 'have-nots', i.e. those that have penises and those that don't. And they have obviously concluded that the haves are superior. Men draw their machismo from the fact that they have a penis. So let's find out what the big deal is, but you'll have to take a short lesson in biology. 

Male sexual anatomy 

The penis is a cylindrical organ with three columns of spongy tissue. Each
column is filled with cavities capable of temporarily storing blood. When a man is sexually aroused, blood pours into these cavities, the penis stiffens and enlarges and the result is an erection or a "hard-on." 

The tip of the penis, known as the glans, has numerous nerve endings and is very sensitive unlike the body of the penis. There is a fold of skin called the foreskin that covers the glans, but can be pulled back. This flap of skin is removed during circumcision. Other than being a religious rite, circumcision is also done from the point of hygiene.  Tiny glands in the penis secrete a cheeselike substance called smegma, which provides a good environment for bacteria. If a man is not circumcised, he should pull back the foreskin and clean the area regularly. 

The testes, popularly known as the family jewels, are walnut-sized glands enclosed in a thin-walled pouch of dark skin known as the scrotum. When a man is aroused, blood rushes to both his penis and his testes. The testes can become very sensitive and painful if a man is aroused without experiencing orgasm or ejaculation. This condition is known as having "blue balls" in slang. However, even if a man does not orgasm, the swelling disappears on its own. The testes produce millions of mature sperm every day once a man hits puberty. 

The prostate gland controls urination and ejaculation. It also produces a milky, alkaline fluid that forms the main portion of the seminal fluid or semen. Semen is rich in amino acids and sugars. The sugars energize the sperm and activate them. At the time of ejaculation, about 1 teaspoonful of semen is released along with about 300 million sperm. 

You may notice a small amount of clear fluid that leaks out from the head of your penis when you're mildly aroused, prior to intercourse. This secretion is produced by the Cowper's glands and may contain some sperm. It can lead to pregnancy even if you do not ejaculate. 
                      

P.S. Size doesn't matter 

Men often measure machismo by the length of their penises. The motto seems to be "bigger is better." It is assumed that the larger a man's penis, the more he can satisfy a woman sexually. Men can relax if they think their equipment is a little lacking in the size department. Bigger is not necessarily better. It's not how big it is, but what you do with it that counts. The fact is that the inner part of the female vagina is not sensitive at all and cannot feel the penis during intercourse. As long as your penis can stimulate the outer vaginal nerves, it's good enough.