Rectus adominis is inserted into –
**Core Concept**
The rectus abdominis muscle is a long, flat, and parallel-fibered muscle in the anterior abdominal wall, playing a crucial role in respiration, posture, and movement of the trunk. It is one of the four muscles in the rectus sheath, which is a fibrous compartment containing the rectus abdominis and pyramidalis muscles.
**Why the Correct Answer is Right**
The rectus abdominis muscle originates from the xiphoid process and the 5th to 7th costal cartilages and inserts into the pubic crest and the pubic tubercle, providing a firm attachment to the pubic bone. This insertion is essential for the muscle's function in rotating the pelvis, stabilizing the trunk, and facilitating movement of the abdominal contents.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the external oblique muscle, not the rectus abdominis, inserts into the pectoralis major and serratus anterior muscles via the costal cartilages.
* **Option B:** This option is incorrect because the internal oblique muscle inserts into the inguinal ligament and the pectineal line of the pubic bone, not into the rectus sheath.
* **Option C:** This option is incorrect because the transversus abdominis muscle inserts into the inguinal ligament and the pectineal line of the pubic bone, not into the rectus sheath.
**Clinical Pearl / High-Yield Fact**
In clinical practice, it's essential to recognize the anatomy of the rectus abdominis muscle, as its insertion into the pubic crest and tubercle is crucial for the repair of abdominal wall hernias, such as the direct inguinal hernia.
**Correct Answer:** D. The pubic crest and pubic tubercle.