Nerves of the arm
Five nerves serve the arm. The musculocutaneous nerve works the biceps, and the axillary nerve winds round the neck of the humerus to the deltoid. The radial nerve spirals round the back of the humerus to the muscles that straighten the elbow, wrist and fingers. Crushed against the bone, it leaves the wrist hanging.
The skin of the right arm from the front and the back, coloured by the nerve that supplies each area, after Gray's Anatomy, 20th edition, 1918, figures 812 and 814Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray812and814.svg)
The median nerve runs down the forearm and through the carpal tunnel at the wrist, where swelling can squeeze it and numb the thumb, index and middle fingers. The ulnar nerve passes behind the bony point of the elbow, the funny bone, where a knock tingles the little finger, and works most of the small muscles of the hand.
The nerves of the palm: the median nerve and its branches to the thumb side, the ulnar nerve to the little finger side, Gray's Anatomy, 20th edition, 1918, figure 815Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray815.png)
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), section on the pectoral girdle and upper limb.
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