**Core Concept**
The extrinsic muscles of the tongue play a crucial role in its movement and function. The intrinsic muscles of the tongue are responsible for altering its shape, while the extrinsic muscles control its position and movement within the oral cavity.

**Why the Correct Answer is Right**
The extrinsic muscles that aid in depressing the tongue are primarily the genioglossus muscles. These muscles originate from the mental spine of the mandible and insert into the lateral surface of the body of the tongue. When the genioglossus muscles contract, they pull the tongue downward, facilitating tasks such as swallowing and speaking.

**Why Each Wrong Option is Incorrect**
* **Option A:** The hyoglossus muscles primarily help to depress the tongue, but they also help to retract and posteriorly displace the tongue. They are not the primary muscles responsible for depressing the tongue.
* **Option B:** The styloglossus muscles help to retract the tongue and are not primarily involved in depressing it.
* **Option C:** The palatoglossus muscles help to elevate the tongue and are not primarily involved in depressing it.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the extrinsic muscles of the tongue work synergistically with the intrinsic muscles to facilitate various tongue movements and functions.

**Correct Answer:** A. Genioglossus muscles.