Pigs are highly successful omnivores, possessing a feeding mechanism specifically adapted to their foraging lifestyle. The process of eating is a complex sequence, beginning with finding food, followed by processing it, and culminating in swallowing. This entire sequence relies on a coordinated system of muscles, each performing a distinct and powerful function. These muscular structures are built to handle everything from delicate searching to forceful grinding of tough materials.
The Specialized Musculature of the Snout for Rooting
The most distinguishing aspect of the pig’s feeding apparatus is the snout, which is uniquely modified for rooting—the act of digging and manipulating food found beneath the soil surface. This ability is made possible by a specialized bone, the os rostri or rostral bone, a small, cartilaginous bone embedded in the snout’s disc that provides a rigid support structure. The bone acts as a shovel or wedge, allowing the pig to exert significant upward and lateral force against the ground without collapsing the nasal structure.
The movement of this reinforced snout is controlled by a set of powerful facial muscles. The levator nasolabialis and the levator rostri are two primary muscles responsible for the vertical and lateral movement of the snout disc. The levator rostri is particularly well-developed, attaching to the dorsolateral part of the rostral bone, enabling the forceful upward and backward thrust required for effective digging and lifting of soil.
The cooperative contraction of these muscles provides the strength and mobility necessary for prehension, the gathering of food. This muscular arrangement also helps in expanding the nostrils to enhance olfaction while the snout is buried in the soil, which is a significant part of the food-finding process.
Power and Mechanics of Mastication Muscles
Once food is gathered by the snout, the next stage involves powerful mastication, or chewing, necessary to break down the fibrous roots, nuts, and other hard materials that constitute a significant part of the pig’s diet. The primary muscles of mastication are the masseter, temporalis, and pterygoid muscles, which collectively generate the high occlusal force needed for grinding. These muscles are innervated by the mandibular branch of the trigeminal nerve.
The masseter muscle is exceptionally large and prominent, reflecting its importance in jaw closure and generating the most significant biting force. Its fibers contribute to both the elevation and protrusion of the mandible, aiding in the initial crushing of food. The temporalis muscle assists in elevating the jaw and is particularly involved in retraction, pulling the mandible backward.
The medial and lateral pterygoid muscles work in conjunction with the masseter to provide the lateral, side-to-side movement essential for grinding. The medial pterygoid aids in elevation and creates the powerful medial force required for the shearing and grinding action. The coordinated activation of these muscles allows the pig to process tough food by combining vertical force with a strong transverse movement of the jaw.
Tongue Function and the Process of Swallowing
Following mastication, the tongue manipulates the processed food into a bolus ready for swallowing. The tongue is composed of both intrinsic and extrinsic muscles, which work together to change the organ’s shape and position within the oral cavity. Intrinsic muscles, such as the longitudinalis superior and transversus linguae, are responsible for shaping the tongue, allowing it to conform to the food and pack the chewed particles together.
The extrinsic tongue muscles, including the genioglossus, hyoglossus, and styloglossus, originate outside the tongue and provide the primary force for movement. The genioglossus and styloglossus are involved in the rhythmic activity seen during chewing. The genioglossus plays a role in protrusion and depression of the tongue base, while the styloglossus helps with elevation and retraction. This coordinated action effectively moves the food bolus to the back of the throat, initiating deglutition.
Swallowing itself is a complex, multi-stage muscular event involving the pharynx. Once the tongue propels the bolus into the pharynx, the process becomes largely involuntary. The pharyngeal constrictor muscles contract sequentially, creating a wave-like motion to propel the food safely into the esophagus. Muscles like the tensor veli palatini and levator veli palatini coordinate to elevate the soft palate, which seals off the nasal cavity and protects the airway during this final step of the feeding process.