The narrowest part of the eustachian tube is the junction between the cartilaginous and the bony part. In children, the eustachian tube is more straight, horizontal and wider. This any infection can go from pharynx to middle ear very easily. Function What is the function of the eustachian tube. Ventilation and drainage of middle ear. Any infection of sinus, nose or pharynx can reach the middle ear through eustachian tube. Torus tubaris tubaris. A bulb is produced by the cartilaginous part of the --