The portal vein is the primary route for blood to flow into the liver. It being patent means there's no clot and blood is flowing freely through the vessel.Hepatopetal denotes flow of blood towards the liver, which is the normal direction of blood flow through the portal vein. The purpose of this guide is to provide you with basic information about filing a utility patent application with the USPTO. A stepbystep overview of a patent application and maintenance process. The five stages of a patent process. This tutorial will focus on patents and the process for securing a patent in the U.S. First, let's consider why we have a patent system? What are the types of patent applications? There are three types of patent applications, namely invention, utility model, and design. It is possible to prepare and file your own provisional patent application.