The abdominal muscle nearest the midline is the
a. external oblique.
b. internal oblique.
c. rectus abdominis.
d. transversus abdominis.
The correct answer and explanation is :
The correct answer is:
c. rectus abdominis.
Explanation:
The rectus abdominis is the abdominal muscle located closest to the midline of the body. It is a long, flat, paired muscle that extends vertically along the anterior abdominal wall, running from the pubic symphysis and pubic crest to the xiphoid process of the sternum and costal cartilages of ribs 5–7. It is enclosed within the rectus sheath, formed by the aponeuroses of the lateral abdominal muscles.
This muscle is commonly referred to as the “six-pack” muscle due to the presence of tendinous intersections that create visible segments when well-defined. The rectus abdominis plays a crucial role in trunk flexion, allowing the body to bend forward. It also assists in stabilizing the pelvis and maintaining posture. Additionally, it is involved in forced expiration, coughing, and straining activities such as lifting, defecation, and childbirth.
The other abdominal muscles serve different functions and are located more laterally:
- External oblique – The outermost abdominal muscle, located on the sides of the abdomen. It helps in trunk rotation and lateral flexion.
- Internal oblique – Positioned beneath the external oblique, it functions in trunk rotation and stabilization.
- Transversus abdominis – The deepest of the abdominal muscles, wrapping around the abdomen like a corset. It primarily provides core stability and supports abdominal contents.
Since the rectus abdominis is the muscle closest to the midline and primarily responsible for trunk flexion, it is the correct answer.