Which of the following muscles is located in the anterior region of the neck and is responsible for flexing the neck and rotating the head to the opposite side?

• A. Sternocleidomastoid
• B. Trapezius
• C. Temporalis
• D. Masseter

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by identifying the anatomical location of each muscle listed in the options. The sternocleidomastoid is located in the anterior region of the neck, while the trapezius is located in the posterior region of the neck and upper back. The temporalis and masseter are muscles of mastication located in the head and jaw region.
2. Step 2: Understand the function of each muscle. The sternocleidomastoid is responsible for flexing the neck and rotating the head to the opposite side. The trapezius primarily moves the scapula and supports the arm. The temporalis and masseter are involved in chewing and jaw movement.
3. Step 3: Match the function described in the question to the correct muscle. The question specifies flexing the neck and rotating the head to the opposite side, which aligns with the function of the sternocleidomastoid.
4. Step 4: Eliminate incorrect options based on their anatomical location and function. The trapezius, temporalis, and masseter do not perform the actions described in the question.
5. Step 5: Conclude that the correct answer is the sternocleidomastoid, as it is located in the anterior region of the neck and performs the specified actions of flexing the neck and rotating the head to the opposite side.