## **Core Concept**
The **hyoglossus muscle** is one of the extrinsic muscles of the tongue, which plays a crucial role in tongue movement. It is innervated by the **cranial nerve XII (hypoglossal nerve)**. The muscle originates from the **hyoid bone** and inserts into the tongue.

## **Why the Correct Answer is Right**
The hyoglossus muscle originates from the body and greater horn of the hyoid bone and inserts into the **side of the tongue**. This insertion allows it to facilitate actions such as tongue depression and retrusion. The muscle's insertion into the tongue is critical for its function in manipulating food and facilitating speech.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the hyoglossus does not insert into the **mandible**; it is related to the hyoid bone for its origin, not insertion.
- **Option B:** This option is incorrect as the **stylohyoid ligament** is not the site of insertion for the hyoglossus muscle; it's related to another muscle (stylohyoid muscle).
- **Option D:** This option is incorrect because the **greater cornu of mandible** is not associated with the insertion of the hyoglossus; it's more related to the attachment of other muscles and ligaments.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **hyoglossus muscle** helps in **depressing and retracting the tongue**. Damage to the hypoglossal nerve (cranial nerve XII), which innervates this muscle, can lead to difficulties in tongue movement, affecting speech and swallowing.

## **Correct Answer:** .
**Correct Answer: D. side of the tongue**