Sternohyoid is supplied by
**Core Concept**
The sternohyoid muscle is a strap muscle of the neck, involved in the movement of the hyoid bone and the sternum. It plays a crucial role in the function of the suprahyoid muscles, which are responsible for the elevation of the larynx and the movement of the hyoid bone during swallowing and speech.
**Why the Correct Answer is Right**
The sternohyoid muscle is supplied by the ansa cervicalis nerve, a branch of the cervical plexus. The ansa cervicalis is formed by the ventral rami of the C1-C3 spinal nerves, and it innervates the infrahyoid muscles, including the sternohyoid, sternalis, and omohyoid muscles. This nerve supply allows for the coordinated movement of these muscles during various activities such as swallowing and breathing.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the sternocleidomastoid muscle is supplied by the accessory nerve (cranial nerve XI) and the cervical plexus, not the ansa cervicalis.
**Option B:** This option is incorrect because the trapezius muscle is supplied by the accessory nerve (cranial nerve XI), not the ansa cervicalis.
**Option C:** This option is incorrect because the scalene muscles are supplied by the cervical plexus, specifically the C3-C5 spinal nerves, but not the ansa cervicalis.
**Clinical Pearl / High-Yield Fact**
The ansa cervicalis nerve is a critical structure in the neck, and damage to this nerve can result in weakness or paralysis of the infrahyoid muscles, leading to difficulties with swallowing and breathing.
**Correct Answer:** C.