Final answer:
The interior intercostals run in the inferior-posterior direction and play a role in expiration by constricting the rib cage.
Step-by-step explanation:
The interior intercostals run in the inferior-posterior direction. This means they run downward and toward the back of the body.
Intercostal muscles, including the interior intercostals, are found between the ribs. There are three sets of intercostal muscles: superficial external intercostals, internal intercostals, and innermost intercostals.
Contrary to the superficial external intercostals that aid in inspiration by raising the rib cage, the interior intercostals play a role in expiration by drawing the ribs together to constrict the rib cage.