Final answer:
The external opening to the canal refers to an anatomical feature related to the three layers of abdominal muscles: the external oblique, internal oblique, and transversus abdominis, which play roles in trunk movement and organ protection.
Step-by-step explanation:
The external opening to the canal mentioned is related to the anatomy of the abdominal muscles, which are part of the antero-lateral wall of the human abdomen. These muscles are the external oblique, the internal oblique, and the transversus abdominis.
The external oblique is the most superficial of these three layers, characterized by its direction extending inferiorly and medially. These muscles facilitate the movements and rotations of the trunk, as well as provide protection to the internal organs in a region where there is no bony encasement.
The slit in the aponeurosis of the external abdominal oblique muscle is likely referring to anatomical structures such as the inguinal canal or openings for nerves and vessels to pass through.
The complete question is: The external opening to the canal is a slit in the aponeurosis of the external abdominal oblique m. is: