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The carpal tunnel is a confined space in the wrist in which the median nerve passes through from the forearm to the hand. Several tendons also pass through it, each with a special slippery covering that allows the tendons to glide smoothly as the fingers are moved. In a normal wrist, there is adequate room in this tunnel for both the tendons and the nerve.
What Is the Carpal Tunnel? -- The AnatomyThe carpal tunnel is a confined space in your wrist. It is much like a tunnel you drive your car through, with a ceiling, floor, walls, an entrance, and an exit. The "walls" and "floor" are made up of bones. The transverse carpal ligament is the tough "ceiling" of the carpal tunnel.
Running from the forearm to the hand and through the carpal tunnel is the median nerve, which controls some of your hand muscles and allows you to feel sensations with your hand. Carpal tunnel syndrome occurs when the median nerve becomes pressed or squeezed at the wrist.
Several tendons (nine to be exact) also pass through the carpal tunnel. These tendons attach specific muscles in the forearm to bones in the hand that allow you to flex your fingers and thumb. Each tendon has a special slippery covering, called the synovium, which allows the tendons to glide smoothly as you move your fingers.
In a normal wrist, there is adequate room in the carpal tunnel for both the tendons and the median nerve. But conditions can happen that can narrow the space and cause problems for the median nerve. For example, the synovium may become inflamed (known medically as synovitis). This can cause the synovium to thicken, which can cause increased pressure on the median nerve.