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For the processor architecture, see ARM (computing)

An arm is a particular upper limb appendage having varying usage and strength within the animal kingdom. In humans it is made up of three distinct bones:

  • Humerus: (upper arm)
  • Radius: (outer bone of the forearm, when supinated)
  • Ulna: (inner bone of the forearm, when supinated)

The hands have these bones:

  • Carpals: ("wrist bones,"
  • Metacarpals: (longer bones in the "palm")
  • Phalanges: (s. phalanx; two in the pollex, or thumb; three four the remaing four fingers)

The upper region of the arm has the following muscles:

  • Deltoid ("shoulder", anterior, lateral, and posterior sections)
  • Biceps brachii (the front, two heads)
  • Triceps brachii (the back, three heads)

The forearm has these muscles:

  • Brachioradialis (connects
  • Supinator (turns forearm up)
  • Pronator quadratus (turns forearm down)
  • Flexor carpi radialis (flexes forearm)
  • Flexor digitorum superficialis (flexes fingers)
  • Flexor pollicis longus (flexes thumb)
  • Extensor carpi radialis longus and brevis (straightens forearm)
  • Extensor carpi ulnarus (straightens forearm)
  • Extensor digitorum (straightens fingers)

Also, the hands have many muscles for fine control of the fingers.