Final answer:
The highlighted structure is the rectus abdominis muscle that is a part of the anterior abdominal muscles.
Step-by-step explanation:
The highlighted structure is the rectus abdominis, which is a part of the anterior abdominal muscles. It is covered by a connective tissue called the rectus sheath. The rectus abdominis muscle is located medially in the abdomen and extends through the entire length of the trunk.