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.
Going out from the center bore is the center disc. This is the portion of the wheel into which the bolt holes are machined to create the bolt circle. This area is the point of contact to the axle seat, the lug bolts and the lateral surface of the rotor. Everything on the wheel connects in some manner to the disc.