All muscles of tongue are supplied by hypoglossal nerve except –
**Core Concept**
The **hypoglossal nerve** is the primary motor nerve responsible for supplying the muscles of the tongue, enabling movements such as protrusion, retraction, and manipulation of food. However, one muscle of the tongue is exempt from this innervation pattern. The exemption is rooted in the embryological origin and functional distinction of the tongue muscles.
**Why the Correct Answer is Right**
The correct answer hinges on understanding that the **palatoglossus muscle**, which is one of the muscles of the tongue, does not receive its motor supply from the **hypoglossal nerve**. Instead, it is innervated by the **vagus nerve** via the pharyngeal plexus, reflecting its role in elevating the tongue and, by extension, participating in the initiation of swallowing.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the genioglossus, hyoglossus, and styloglossus muscles are all indeed supplied by the hypoglossal nerve.
**Option B:** This option is incorrect for similar reasons as option A, focusing on the incorrect attribution of nerve supply.
**Option C:** This option might seem plausible but is incorrect as it does not accurately represent the exception to hypoglossal nerve supply.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **palatoglossus muscle** is unique among the tongue muscles due to its innervation by the **vagus nerve**, underscoring the complex interplay of cranial nerves in orchestrating the functions of the oral cavity and pharynx.
**Correct Answer:** Correct Answer: D. Palatoglossus.