Normal penis size and penis anatomy
In general, and despite some minor international variations, the normal measurements of the penis are 3.6 - 4 inches (9.1 - 10.1 cm) for the flaccid penis, 4.6 - 5.2 inches (11.7 - 13.2 cm) for the stretched penis, and 5.6 - 6.4 inches (14.2 - 16.3 cm) for the erect penis, with a girth of 3.6 - 4 inches (9.1 - 10.1 cm) for the flaccid penis and 4.6 - 6 inches (11.7 - 15.2 cm) for the erect penis. While the penis is flaccid, the best way to estimate its erect length is to pull back the fat pad that may be covering it, stretch the penis, and measure it from the lower edge of the pubic bone to the tip of the glans.
There is no correlation between the size of the penis and the size of the nose, foot, fingers, or any other body part. Although the size of the penis varies from man to man, it probably has less relationship, physically or structurally, to other parts of a man's body than any other bodily component. Measurement of flaccid size may not be a valid test to assess the true length of the penis. Many men with large flaccid penises experience relatively little growth in erectness, whereas the man with a smaller flaccid penis sees a dramatic change in size on becoming erect.
Micropenis - unusually small penis
Medically speaking, most so-called micropenises are actually normal sized and may simply be buried in the dense suprapubic fat (fatty tissue above the pubic bone) usually found in obese men. The procedure to lengthen these penises is relatively simple. When the suprapubic fat pad is pulled upward, the penis is usually found to have a normal length. For those men, exercise and diet alone may reduce the fat pad and provide natural penile elongation without the need for any medical or surgical treatment.
In exceptional cases, when the penis is truly small - measuring less than 1.8 inches (4.6 cm) in the flaccid state and less than 2.8 inches (7.1 cm) during erection - we have an abnormal condition defined as micropenis. It is a multifactorial disorder caused by genetic, hormonal, and environmental abnormalities. It can also be associated with ambiguous genitalia or malformations such as hypospadias (an abnormal location of the urethral opening).
Peyronie's disease - unusual penile curvature or bending
First described by French physician, Francois de la Peyronie, in 1743, this condition is characterized by a plaque or a patch of scar tissue that forms on the tunica albuginea and penetrates into the cavernous tissue. This plaque, depending on its location, may cause penile curvature (usually dorsal, possibly other directions) or sometimes an hourglass appearance due to indentation in the middle of the shaft, with possible narrowing from the indentation toward the glans penis. This deformity may lead to vascular anomalies, which may result in erectile dysfunction. If untreated for a long time, about 40% of Peyronie's disease cases progress, about 47% do not change, and about 13% spontaneously regress.
Currently the most accepted theory of the etiology of Peyronie's disease is that repeated physical trauma during intercourse leads to bleeding, deposition of fibrin (a blood substance involved in the clotting process), inflammation in the tunica or beneath it at the septum dividing the corpora cavernosa, and overproduction of cytokines by inflammatory cells such as T-lymphocytes.
Penis erection process
An erection does not occur on demand at a snap of the fingers. Several systems in the body and the mind team up to produce an erection. The anatomy of the penis is the foundation, but erection has certain other prerequisites: an intact neurovascular system, absence of medical or psychogenic disturbance, confidence, intimacy, receptivity, excitement, and physical attraction. Physical and psychological stimulation are also required. If any of the involved mechanisms fail, an erection can become difficult or impossible to achieve or to maintain, resulting in erectile dysfunction.
Erection occurs when nerve impulses from the brain (psychogenic erection) and from genital stimulation (reflexogenic erection) combine to cause blood to flow faster into than out of the penis. Your penis is a sophisticated hydraulic system. There are three sponge-like cylindrical bodies that run the length of your penis, which are fed blood from small branches of the penile artery into the spongy tissue. These three tubes swell with blood to cause an erection. Two of these tubes, the corpora cavernosa, lay side by side along the shaft of your penis, and the third is the corpus spongiosum, which lies underneath. Together these three cylinders make up the shaft of your penis.
An erection happens by relaxing the microscopic muscles that surround the arteries in the penis, causing dilation of the arteries. Blood rushes into the spongy tissues, creating a hydraulic elevation of your penis. Simultaneously, muscles near the base of your penis contract, preventing blood from leaving your penis.