How do the hands and wrists work?
The movement and power of your hand and wrist are controlled by muscles and tendons:
- The flexor group, on the inside or front of the arm, control bending of your fingers and wrist – these pass over the front of your wrist and are held in place by a strong fibrous band called the flexor retinaculum, or carpal tunnel ligament.
- The extensors on the outside or back of your forearm allow the hand to open up.
- Small muscles in your hand (the lumbricals and interossei) allow fine movement.
The tendons in your hand are covered by a layer of synovium, the same tissue that lines your joints. The tendon and synovium are covered by a tendon sheath, which is a bit like the protective covering on the brake cable of a bicycle.
The sense of touch in your hand is supplied by two main nerves:
- Your median or carpal tunnel nerve passes under your carpal tunnel ligament and gives feeling to most of your hand (from your thumb to half of your ring finger). It also provides power to muscles at the base of your thumb.
- Your ulnar or 'funny bone' nerve gives feeling to your little finger and half your ring finger, and it powers all of the other small muscles in your hand.
There are also two arteries (radial and ulnar) that supply blood to your hand. You can feel these on the palm-side of your wrist. The radial artery (nearer your thumb) is often felt to take your pulse. The ulnar artery on the opposite side of your wrist is much more difficult to feel.