Final answer:
The tongue is the prehensile part of the equine mouth that helps in grasping and manipulating food, which is essential for chewing and swallowing.
Step-by-step explanation:
The part of the equine mouth that plays a prehensile role is primarily the tongue. In horses, as in many other animals, the tongue is a versatile and strong organ used for manipulating food. It's not just about taste; the tongue also aids in collecting food into a bolus, adjusting its position for optimal chewing, and is essential for swallowing. The prehensile quality of the tongue allows horses to grasp and pull forage and directs food and water for processing in the oral cavity.
Other important structures in the horse's mouth include the cheeks and lips, which help in keeping food within the mouth while chewing. The anatomy and functionality of these parts are vital for the horse’s digestive process, starting right from the prehension of food. In detail, the lips cover the orbicularis oris muscle that controls the intake and output of matters in the mouth, while the cheeks, with internal buccinator muscles, play a critical role in maintaining the food in place during mastication.