When you look at diagram of a nerve like radial nerve it looks like a mostly straight line that runs through the arm. how does it actually connect to the nerve endings in the skin? are there multiple branches/fibers from it that directly connect?

Branches: The radial nerve gives off multiple branches to provide motor function to multiple muscles in the forearm and posterior arm as well as multiple sensory branches that innervate the posterior arm, the posterior forearm and the dorsal surface of the lateral three and a half digits of the hand, so much more like branching tree than straight line.

Nerve 2 skin?: Great Wikipedia question. Big nerves branch into smaller ones and they branch into smaller ones and then even smaller ones till a single fiber branch reaches say a pain receptor. When something touch’s that pain receptor it releases chemicals that move out of the cell and bind to the nerve fiber. When enough gets there brains says PAIN! and sends signal to move away (from a fire say).