The teeth in the throat are pharangial teeth. They are basically plates in the throat much like the tooth plates that you see in the front of your rtc mouth. They are just rough plates feel like sand paper. However that being said, The teeth in your rtc mouth versus the pharangial teeth. The teeth in the front are for grasphing things while the rtc swallows them. The ones in the throat are designed for crushing. RTCs in the wild eat freshwater crabs and mussels along with other crustacians. The pharangial teeth are located between the gill rackers at the back of the head. They have the chest muscle of the overly large clavicals, and other internal muscle to generate force. Notice that your rtc are thickest at this point of their body. That's where the strongest point is. They can crush mussel shells, and crabs like nothing. They will also use it to crush up a large fish' skull before attempting to swallow it. All that said you are likely to only get scrapes from the mouth teeth if your arm goes in, but if your arm goes it to the pharangial teeth it could definitely break your hand or arm without even trying. Flathead catfish(Polydicitis olivarius) are a large catfish here in the USA people noodle for them and there are several cases where they have broken arms or hands, and athey are no where near the bulk of a rtc the same size. Hope this helps clear up any confusion. I don't just keep large catfish I also study the anatomy and physiology so if you guys ever have any questions ask and I will try to answer or point you in the right direction.