Great. This should help your scene.
"Carpal" means "of or relating to the wrist." The carpal tunnel is a tunneled opening through the cage-like structure of thick connective tissue on the inside of the wrist--palm side, where the forearm meets the hand. It's the same general area where people feel for a pulse in the wrist.
If you are looking down at your wrist (palm up), the tight cage is made of a floor of wrist bones underneath and a ceiling of tough, fibrous ligament on top. That's the transverse carpal ligament [a.k.a. flexor retinaculum or anterior annular ligament], and it extends between the hook of the hamate & the pisiform on the pinky side to the tubercles of the scaphoid and trapezium on the thumb side. These bones are part of a set called the "carpals," because they are the bones of the wrist itself.
Picture of carpal bones here:
http://droualb.faculty.mjc.edu/Cour...siology 50/Lecture outlines/05_23Figure-L.jpg
The space between the transverse carpal ligament and the carpal bones is a fixed space. There is not much, if any, stretch on any side, so if things start to swell, there is nowhere for the pressure to go except compressing other structures in the tunnel.
Picture of carpal tunnel (under transverse carpal ligament) here:
https://gymnasticsinjuries.files.wordpress.com/2013/09/carpaltunnel.gif
These are the primary components of the tunnel:
-Flexor Digitorum Superficialis tendons (four in total)
-Flexor Digitorum Profundus tendons (four in total)
-Flexor Pollicis Longus tendon (one tendon)
-Median nerve, both sensory and motor components (sensory is to lateral 3 1/2 digits and palm, motor is to hypothenar muscles and lateral two lumbricals)
Of note for potential dialogue purposes, the ulnar nerve (the other main nerve serving the hand) passes through Guyon's canal, which is like a side entrance to the wrist over and above the carpal tunnel. That means the ulnar nerve does not go through the carpal tunnel. Same for the ulnar artery. The ulnar nerve and artery can get compressed as well, but that is a different syndrome from CTS.
Picture of Guyon's canal here:
http://www.eorthopod.com/images/ContentImages/hand/hand_guyon_canal/hand_guyon_canal_anat02.jpg
[note that "flexor retinaculum" is another term for "transverse carpal ligament"--same thing]
So, for your purposes, you probably want to describe effects on one or more of the four sets of structures that do pass through the carpal tunnel. CTS particularly is about compression of the median nerve, often secondary to inflammation/swelling of one or more tendons in the carpal tunnel. Does this make sense so far? Is it helpful, or am I just yammering to hear myself talk? I do that sometimes. I'm old enough that I can't tell anymore.