Anatomical variations

The human body is composed of a typical pattern of anatomy, yet every structure varies in form from person to person. For example, humans develop with a standard set of defined muscles, yet the shape and mass of each muscle varies significantly among individuals. Sometimes, "anatomical variations" develop – that is, anatomical structures that do not conform to the typical range of regular morphology (for example, an entirely separate "extra" muscle that develops in one person).

Human anatomy is so intricate that the prevalence of an anatomical variation is thought to be certain in every indivi...