Gluteal region

The buttocks (singular: buttock) are two rounded portions of the anatomy, located on the posterior of the pelvic region of primates (including humans), and many other bipeds or quadrupeds, and comprise a layer of fat superimposed on the gluteus maximus and gluteus medius muscles. The two gluteus maximus muscles stabilise the hip joint and are the largest muscles in the entire human body; responsible for propelling the entire body forward when running and walking, ensuring the proper functioning of the entire leg. Physiologically, the buttocks enable weight to be taken off the feet while sitting. In many cultures, they play a role in sexual attraction. Some cultures, such as that of Victorian England, have also used the buttocks as a primary target for corporal punishment, as the buttocks' layer of subcutaneous fat offers protection against injury while still allowing for the infliction of pain. There are several connotations of buttocks in art, fashion, culture and humor, and the English language is replete with many popular synonyms that range from polite colloquialisms ('posterior', 'backside' or 'bottom') to vulgar slang ('arse,' 'ass,' 'bum,' 'butt,' 'booty,' 'prat'). In humans the buttocks are located between the lower back and the perineum. The buttocks are formed by the masses of the gluteal muscles or 'glutes' (the gluteus maximus muscle and the gluteus medius muscle) superimposed by a layer of fat. The superior aspect of the buttock ends at the iliac crest, and the lower aspect is outlined by the horizontal gluteal crease. The gluteus maximus has two insertion points: ​1⁄3 superior portion of the linea aspera of the femur, and the superior portion of the iliotibial tractus. The masses of the gluteus maximus muscle are separated by an intermediate intergluteal cleft or 'crack' in which the anus is situated. The buttocks allow primates to sit upright without needing to rest their weight on their feet as four-legged animals do. Females of certain species of baboon have red buttocks that blush to attract males. In the case of humans, females tend to have proportionally wider and thicker buttocks due to higher subcutaneous fat and proportionally wider hips. In humans they also have a role in propelling the body in a forward motion and aiding bowel movement. Some baboons and all gibbons, though otherwise fur-covered, have characteristic naked callosities on their buttocks. While human children generally have smooth buttocks, mature males and females have varying degrees of hair growth, as on other parts of their body. Females may have hair growth in the gluteal cleft (including around the anus), sometimes extending laterally onto the lower aspect of the cheeks. Males may have hair growth over some or all of the buttocks. The English word of Greek origin 'callipygian' indicates someone who has beautiful buttocks. Depending on the context, exposure of the buttocks in non-intimate situations can cause feelings of embarrassment or humiliation, and embarrassment or amusement in an onlooker (see pantsing). Willfully exposing one's own bare buttocks as a protest, a provocation, or just for fun is called mooning. In many punitive traditions, the buttocks are a common target for corporal punishment, which can be meted out with no risk of long-term physical harm compared with the dangers of applying it to other parts of the body, such as the hands, which could easily be damaged. Within the Victorian school system in England, the buttocks have been described as 'the place provided by nature' for this purpose. A modern-day example can be seen in some Southeast Asian countries, such as Singapore. Caning in Singapore is widely used as a form of judicial corporal punishment, with male convicts being sentenced to a caning on their bare buttocks.