Final answer:
The external intercostal groove contains blood vessels and nerves that supply the external intercostal muscles, which help in the inspiration of air during breathing by raising the rib cage.
Step-by-step explanation:
The external intercostal groove contains blood vessels and nerves that supply the external intercostal muscles, which are involved in the process of breathing. These muscles aid in inspiration by raising the rib cage, expanding it to allow air to flow into the lungs. The external intercostals are one of three sets of muscles spanning the intercostal spaces, with the internal intercostals and innermost intercostals being the other two.
The external intercostals are located laterally on the sides of the body and are superficial to the internal intercostals. The internal intercostals are found medially near the sternum, while the innermost intercostals, which act as synergists for the internal intercostals, are located deep to these muscles. Together, these muscles facilitate the mechanics of breathing by changing the shape and volume of the rib cage to modify the volume-pressure ratio within the pleural cavities.