Upper limb

The upper limb or upper extremity is the region in a vertebrate animal extending from the deltoid region up to and including the hand, including the arm, axilla and shoulder.In formal usage, the term 'arm' only refers to the structures from the shoulder to the elbow, explicitly excluding the forearm, and thus 'upper limb' and 'arm' are not synonymous. However, in casual usage, the terms are often used interchangeably. The term 'upper arm' is redundant in anatomy, but in informal usage is used to distinguish between the two terms.In the human body the muscles of the upper limb can be classified by origin, topography, function, or innervation. While a grouping by innervation reveals embryological and phylogenetic origins, the functional-topographical classification below reflects the similarity in action between muscles (with the exception of the shoulder girdle, where muscles with similar action can vary considerably in their location and orientation.The skeletons of all mammals are based on a common pentadactyl ('five-fingered') template but optimised for different functions. While many mammals can perform other tasks using their forelimbs, their primary use in most terrestrial mammals is one of three main modes of locomotion: unguligrade (hoof walkers), digitigrade (toe walkers), and plantigrade (sole walkers). Generally, the forelimbs are optimised for speed and stamina, but in some mammals some of the locomotion optimisation have been sacrificed for other functions, such as digging and grasping.