## **Core Concept**
The submandibular gland is primarily innervated by the **facial nerve (cranial nerve VII)**, which provides both motor and secretory fibers. The gland receives its parasympathetic innervation from the **submandibular ganglion**, which is linked to the facial nerve.

## **Why the Correct Answer is Right**
The submandibular gland receives its parasympathetic secretomotor innervation from the **facial nerve (cranial nerve VII)**. The facial nerve's **chorda tympani** branch carries preganglionic parasympathetic fibers that synapse in the **submandibular ganglion**. Postganglionic fibers from this ganglion then innervate the submandibular gland, stimulating saliva production. The **glossopharyngeal nerve (cranial nerve IX)** supplies the **parotid gland** via the **otic ganglion**, not the submandibular gland.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The **facial nerve (cranial nerve VII)** does supply the submandibular gland through its **chorda tympani** and the **submandibular ganglion**.
* **Option B:** The **lingual nerve**, a branch of the **mandibular division of the trigeminal nerve (cranial nerve V)**, provides sensory innervation to the anterior two-thirds of the tongue and also carries the **chorda tympani** fibers to the **submandibular ganglion**, indirectly supporting the gland's function.
* **Option D:** The **submandibular ganglion** itself is directly involved in the innervation of the submandibular gland.

## **Clinical Pearl / High-Yield Fact**
A key clinical point is that damage to the **facial nerve**, particularly its **chorda tympani** branch, can result in decreased salivation by the submandibular gland. The **submandibular gland** is also notable for being the site of **sialolithiasis** (salivary gland stones), which can obstruct saliva flow.

## **Correct Answer:** D. Glossopharyngeal nerve.