Saliva constantly flows from the salivary glands in your mouth. Sometimes, the chemicals in saliva can crystalise to form a tiny stone. Salivary gland stones ('salivary calculi') can become lodged in the duct (tube) leading from the salivary gland, blocking the flow of saliva into the mouth. This can cause swelling and pain in the gland.
Hub assemblies and wheel bearings. Located between the brake drums/discs and the drive axle, the hub assembly is mounted to the holding bracket of the chassis on the axle side. On the drum/disc side, the wheel is connected to the hub assembly via bolts. The wheel bearing itself is inside the hub unit.
Many people use term wheel as a rim meaning the entire metal part to which the tire is mounted because rim and wheel are usually cast or pressed from a single piece of metal. The main difference between wheel and rim is that rim is not the whole wheel but only a part of the wheel. Key parts of the wheel are rim and disc. The hub may be also considered as a part of the wheel. The hub is wheel base with studs on which the wheel is attached to the suspension.