Definition: Also known as butt, is formed by the buttocks, the anus and the rectum. The buttocks are formed by the gluteus maximus, medium and minor.
Its superior parts end at the iliac crest and the bottom one is drawn by the line of the gluteus. Maximum gluteus has two insertion points: 1/3 of the top portion of the femur's iliotibial tract.
The gluteus' muscular mass is separated by a crack where the anus is. This part is the responsible for making different kinds of asses either if they are turned-up, booty or just flat.
The ass allows primates to sit down vertically without having to relay on feet like four legged animals do.
Expressions of the kind kiss my ass refers to anal sex, performed either by man with man as in man with woman.
