There are many ways to group these complex muscles of the forearm and hand. When working in the lab, we must look at all of the muscles together, establish landmarks and subdivide the muscles into groups such as flexors or extensors for easier identification. Further grouping of these muscles such as flexors of the wrist and flexors of the digits can be accomplished by knowing and identifying the distal attachments of these muscles.

Generalizations about these muscles will make your job much easier.

Remember the following:

• Flexors of the wrist and digits attach proximally to the medial epicondyle of the humerus and are innervated by the median nerve.
• Extensors of the wrist and hand attach proximally at the lateral epicondyle of the humerus and are innervated by the radial nerve.
• Extrinsic muscles of the hand arise in the forearm and insert in the wrist or digits.
• Intrinsic muscles of the hand arise and insert in the hand.
• Muscles responsible for supination or pronation must attach to the radius.
• The ulnar nerve is responsible for most of the hand.
• The median nerve is primarily responsible for the thumb.