Final answer:
The mastoid air cells are located in the mastoid process of the temporal bone, which is a prominent bony structure behind the ear canal.
Step-by-step explanation:
The mastoid air cells are located within the mastoid process of the temporal bone. The temporal bone is a complex structure with several different parts including the squamous, mastoid, and zygomatic portions. The mastoid process is a prominent bony projection located behind the ear canal, and it contains the mastoid air cells which are connected to the middle ear and play a role in respiratory function. These air cells also help to regulate air pressure within the ear. The mastoid air cells are important anatomical features related to the auditory system and are adjacent to the structures involved in hearing such as the external acoustic meatus and the internal acoustic meatus, which allow for passage of nerves related to hearing and balance.