Step 1: Understanding the Question:
The image identifies the Digastric muscle (structure A).
The question asks for its nerve supply, which is unique because the muscle has a dual embryological origin. Step 2: Detailed Explanation:
Anatomy of the Digastric Muscle: This muscle consists of two bellies - an anterior belly and a posterior belly - joined by an intermediate tendon.
Embryology and Innervation of the Anterior Belly:
- It develops from the mesoderm of the first pharyngeal arch.
- Consequently, it is supplied by the nerve of the first arch: the Mandibular nerve (CN V3), specifically via its branch, the nerve to the mylohyoid.
Embryology and Innervation of the Posterior Belly:
- It develops from the second pharyngeal arch.
- Consequently, it is supplied by the nerve of the second arch: the Facial nerve (CN VII).
Evaluating the Options: Option B correctly identifies the parent nerves responsible for the two bellies: the Mandibular nerve (for the anterior) and the Facial nerve (for the posterior).
Functional role: Together, these bellies help in depressing the mandible and elevating the hyoid bone during swallowing and speech.
Step 3: Final Answer:
The digastric muscle receives a dual nerve supply from the Facial nerve (posterior belly) and the Mandibular nerve (anterior belly).
