Which action is primarily performed by the rectus abdominis muscle?

• A. Flexion of the vertebral column (trunk flexion) and compression of the abdominal contents
• B. Abduction of the hip at the coxal joint
• C. Elevation of the scapula
• D. Extension of the vertebral column (trunk extension)

Answer: (A)

Verified step by step guidance

1. Step 1: Identify the anatomical location and general function of the rectus abdominis muscle. It is a paired muscle running vertically on each side of the anterior wall of the human abdomen.
2. Step 2: Understand the primary movements associated with the rectus abdominis. This muscle is known for its role in flexing the vertebral column, which means bending the trunk forward.
3. Step 3: Recognize that the rectus abdominis also helps compress the abdominal contents, which is important for actions like forced expiration, defecation, and childbirth.
4. Step 4: Compare the listed options with the known functions of the rectus abdominis. Abduction of the hip, elevation of the scapula, and extension of the vertebral column are actions performed by other muscles, not the rectus abdominis.
5. Step 5: Conclude that the correct action primarily performed by the rectus abdominis is flexion of the vertebral column (trunk flexion) and compression of the abdominal contents.