There has been a complete lack of understanding of this "little piece of extra skin" (which in hindsight isn't so little, nor extra) that covers the glans ("head") of the penis, and how it contributes to the natural mechanics of sexual encounters. Doctors often don't provide this information to new parents, so they are essentially giving their UNinformed consent to have their newborn child circumcised.
Early Development of the Penis and Foreskin
As a child is developing in the mother's womb, the genetic sex was determined at conception, by whether the successful sperm contributed an X chromosome (XX = female) or a Y chromosome (XY = male). However, during the first several weeks, the genitalia will appear relatively undifferentiated -- both boys and girls will look the same during this period. As development progresses (9-12 weeks), the genital folds might remain separated by the urogenital groove to eventually form the labia minora and vagina. Or the folds will rise slightly toward each other, fusing together, enclosing the urogenital grove to eventually form the penis. While that is happening, the glans, which is at one end of the urogenital groove, differentiates into either the glans penis or the glans clitoris, and the tissue surrounding it differentiates into the male foreskin or female clitoral hood. The fact that the glans and the clitoris develop from the same primordial tissue, as does the prepuce of each, is one of several similarities between male and female circumcision.
Fused, Like a Fingernail
As the penis is developing, the foreskin forms being attached to the glans, almost as if it was just another layer of the skin of the glans. Really, it is a completely different type of skin though. If left alone, this natural adhesion to the glans will remain until the child is several years old. In some boys, separation might not occur until puberty, and that is okay - usually. Premature (forced) separation and retraction of the foreskin will rip apart the adhesive membrane, causing pain and sometimes inviting infection. Forced retraction is actually the very first step of the circumcision procedure.
Proper Care of an Intact Foreskin
"If intact, do not retract. Only clean what is seen." There is virtually no reason to retract a boy's foreskin -- not to "clean" it, not to "inspect" it, not to insert a catheter. The age at which the foreskin will naturally separate and become retractable varies widely from individual to individual, sometimes not even until puberty or beyond. Even once the foreskin has separated, retraction might be uncomfortable or painful for the child. The foreskin should only be retracted by the boy himself. It is also important to remember to keep soap use at a minimum around the opening of the foreskin. Soaps can irritate the tissues of the inner foreskin and glans, and might lead to infections. If a soap is to be used -- including bubble baths -- make sure it is a very mild soap, and limit the duration/ frequency of the first several exposures so you can keep an eye open for signs of irritation and infection before it has a chance to get out of hand. Read more about proper intact care.
"Ballooning" is Normal
On some boys, the opening of the foreskin might be slightly too narrow to allow urine to pass through as quickly as it is coming out of the urethra. In these boys, and even occasionally in all boys, this momentary buildup of urine pressure inside the foreskin will cause the foreskin to expand slightly, similar to a balloon being filled with air or water. If the foreskin is no longer adhesed to the glans, the full length of foreskin can expand and the apparent size difference may be startling for the uninitiated. This is normal, and is no cause for alarm, as long as there is a steady urine flow and all the urine empties as the flow slows.
If the urine is being held back to the point where the pressure is painful, the urine stream seems abnormally narrow or inconsistent, or the urine isn't completely voided from the bladder-urethra-foreskin, consult a doctor. This could be a sign of an infection or tissue irritation at some point along the urinary tract.
Functions and Parts of the Foreskin
The foreskin is a very complex structure and plays several very important roles throughout the life of the intact boy and man. Circumcised guys are left without recourse since many of these structures and functions are diminished or completely eliminated from their bodies through the circumcision process.
Protective / Comfort:
The most basic function of the foreskin is the protection it gives the glans simply by being there and covering it up. While nestled inside the foreskin, the glans is kept safe from abrasion on clothing, temperature extremes, and other occasional issues down there. When it is nearly constantly covered by a foreskin, the glans has a considerably more intense color and is much smoother and softer to the touch. When an infant or young boy is circumcised, the connective tissue which fuses the foreskin and glans together is ripped apart, leaving the glans raw and perhaps scarred and pitted. It may be subject to infections and shrinkage. After the initial "healing" from the circumcision it becomes dry and will discolor. Through years of being exposed the glans becomes keratinized, adding additional layers of tissue in order to adequately protect itself, which further contributes to discoloration (and sensitivity loss). Additionally, the soft mucosa (inner foreskin) also plays a role in the immunological defense system. It contains langerhans cells, and cells which secrete immunoglobulin antibodies, as well as antibacterial and antiviral proteins. Circumcision removes many of these cells, as well as lymphatic vessels within that part of the bodies immune system.
Moisturizing:
Skin all over the body has a natural moisture content; some skin types need to stay more moist than others. Think of how uncomfortable and painful it would become if your inner eyelids dried out. Or the inside of your cheeks. Or your lips. The glans and the inner foreskin are similar. When covered as a semi-internal organ by the foreskin, and not exposed to air or clothing, the surface of the glans and inner foreskin are able to retain their moisture and natural deep color. Sebaceous glands on the inner foreskin (though not on all men) may also help moisturize the inner foreskin and glans.
Gliding Action:
The skin of the penis is not anchored to the underlying tissues. With an intact foreskin, there is enough skin along the entirety of the penis to allow for full expansion of the penis during erection, without the skin getting too tight. Additionally, this allows the skin to glide along the length of the penis during sexual activity. Circumcision eliminates this gliding action because of the amount of skin removed -- often there is no looseness at all, and erections can result in painfully tight skin.
Sensory:
At the tip, near the junction of the junction of the inner and outer foreskin, is a group of small, soft, densely innervated ridges known as the ridged band. The foreskin also contains Meissner's Corpuscles by the thousands; the same type of receptors that are responsible for the light-touch sensitivity of specific areas of skin such as the fingertips and lips. The foreskin contains between 10,000 and 20,000 nerve endings of several specialized types, some of which are from branches of the dorsal penile nerve. Together they can detect subtle changes in texture, motion, temperature. Make no mistake, because the foreskin is densely innervated, it is one of the primary erogenous zone of the intact male body. Circumcision removes all of these specialized sensory nerve endings mentioned above. The frenulum is a V-shaped structure on the underside of the glans that tethers the foreskin and helps it pull back over the glans after being retracted; it is also highly erogenous. In every circumcision, the frenulum is severed, with a diminished portion left behind; sometimes a second cut is made to remove it all. Just under the skin but above the corpus cavernosa lies the Dartos Fascia, a temperature-sensitive smooth muscle sheath. Approximately half of this is removed during a circumcision. Destruction of the pudendal nerve is rare but devastating complication of circumcision. The terminal branch of this nerve connects to the skin of the penis, the prepuce, the corpora cavernosa, and the glans. If cut during circumcision, the top two-thirds of the penis will be almost completely without sensation.
Other:
Apocrine glands on the inner foreskin produce pheromones, important biochemical signals to potential sexual partners. It is not yet understood what effect their removal has on human sexuality. The presence of estrogen receptors is a relatively recent discovery, and their function is not yet fully understood. Because circumcision removes the double-layered, loose, and usually overhanging foreskin, making the penile skin tight, it also reduces some of the overall length and girth of the penis. Several blood vessels are completely removed, significantly altering the normal blood flow, which in turn can alter the development and natural function of the penis (particularly the sensory functions). Although rare, some unfortunate boys lose their entire penis, or their life, from circumcision accidents and infections. Circumcision performed during infancy disrupts the mother-child bonding process, and may have significant adverse effects on neurological development and ability to trust other people, puts the newborn into a defensive psychological state and diminishes his self-confidence and hardiness ("learned helplessness" or "acquired passivity"). The trauma of this early pain lowers a circumcised boy's pain threshold below that of intact boys and girls.
For more on these functions, visit this post at Peaceful Parenting.
Sex as Nature Intended
During sexual intimacy, an intact penis moving in and out of its own loose skin facilitates a smooth, comfortable interaction with little to no abrasion of the skin for either partner. Without the foreskin present, the shape and movement of the tight-skinned penis removes whatever natural lubrication was present, often making artificial lubricants necessary. Studies have been done to attempt quantifying the pleasure experienced by a circumcised penis versus an intact one. Some studies say there is a measurable difference, other studies say there is no difference at all. Regardless of what the "studies" say, intact men, with all the nerve endings their penis is supposed to have, along with the supple glans having been protected their entire lives, undoubtedly experience different sensations during sexual activity than their circumcised counterparts.
Restoration
Although the specialized structures and functions of the foreskin cannot be truly restored (yet*), there is a non-surgical process by which men can lengthen the shaft skin and inner foreskin remnant to regain the looseness and gliding action the foreskin would have provided. Many men who are or have restored also report dramatic changes in the color and sensitivity of their glans as the layers of keritinized skin start coming undone. Likewise with the actual circumcision scar - it gets lighter and less noticeable; in some cases completely invisible. This process takes several years of dedicated, daily, gentle "tugging" to complete, but it can be done. A restored "fauxskin" can in some cases be so similar in appearance to an intact foreskin that it would take a close examination by someone who knows the difference to tell them apart. Read more about foreskin restoration.