Students learning about the structure of the U.S. federal court system probably focus more on the geographical divisions of the appeals court more than any other aspect of the system, primarily because that is something upon which I put particular emphasis in our lecture about the system.
While I do mention that there are two other Courts of Appeal in addition to the 11 regional appeals courts, I really do a disservice to the D.C. Court of Appeals by not talking more about it. This court is arguably the second most important court in the federal court system for the reasons set forth in an excellent Q&A put together by The Blog of the Legal Times. Students interested in obtaining a deeper knowledge of the U.S. federal court system should give this a read.