An anatomical duct is a TUBE-like structure that is part of the body's anatomy. It is composed of four parts: a TUBE, an iter, a vas, and an iters. The TUBE is a hollow cylinder that carries substances through the body. The iter is a looping structure that connects two tubes together. The vas is a vessel that carries blood or other fluids. The iters is a larger TUBE that connects the MAIN TUBE to other structures. Finally, the MAIN TUBE is the largest and most important part of the anatomical duct, as it carries the most material.