When you sort the fields in a data list, you add a row at the top of the list that you define as the primary sorting level. The cells in this row contain numbers (from 1 to the number of the last field in the data list) that indicate the new order of the fields.
The temporomandibular joint is the joint of the jaw and is frequently referred to as TMJ. The TMJ is a bilateral synovial articulation between the mandible and temporal bone. The name of the joint is derived from the two bones which form the joint: the upper temporal bone which is part of the cranium (skull), and the lower jawbone or mandible.
Lockjaw from TMJ is a function of the muscles of the jaw being so tight that they either pull the joint out of alignment, or they are so tight that as you open your mouth, they seize/spasm and lock the jaw in place for some length of time.