The salivary glands in the pig are specialized exocrine organs that produce and secrete saliva into the oral cavity. Saliva moistens the oral mucosa and prepares food for digestion. It lubricates the feed bolus for easier swallowing, though the digestive contribution from salivary amylase in pigs is minor compared to the mechanical and lubricating functions. Pigs possess several paired salivary glands, categorized by their size and anatomical position around the head and jaw.
The Four Major Salivary Glands in Pigs
Pigs possess three major paired glands: the Parotid, the Mandibular, and the Sublingual glands. The Zygomatic gland is often discussed in comparative anatomy but is a less prominent structure in pigs. The Parotid gland generally produces a serous, or watery, secretion rich in enzymes, which is essential for the initial mixture with feed.
The Mandibular and Sublingual glands secrete mixed saliva, containing both serous and mucous components. Mucous secretions are thicker, containing glycoproteins that provide superior lubrication for the passage of feed down the esophagus. This blend of watery and viscous saliva ensures pigs can effectively process various types of feed. The Zygomatic gland is functionally represented in the pig by the dorsal buccal glands, which contribute to the overall salivary output near the cheek region.
Detailed Anatomical Placement of Porcine Salivary Glands
The Parotid gland is the largest salivary gland, situated in the caudal (posterior) region of the face. It lies ventrally and anteriorly to the base of the ear cartilage and extends over the masseter muscle. This large, triangular structure does not fully reach the base of the ear in the pig. Its secretion is channeled through the parotid duct, which travels forward across the cheek and penetrates the oral mucosa opposite the fourth or fifth upper cheek tooth.
The Mandibular gland is positioned ventrally and caudally compared to the parotid gland. It is typically found near the angle of the jaw, nestled in the intermandibular space, caudal and medial to the body of the mandible. This gland is often partially covered by the ventral edge of the larger parotid gland. Its location adjacent to the mandibular lymph nodes makes it a reference point for anatomical examination.
The Sublingual gland is located in the rostral (anterior) portion of the oral floor, lying beneath the tongue. This long, narrow gland is situated between the body of the mandible laterally and the genioglossus muscle of the tongue medially. It is closely associated with the main excretory duct of the mandibular gland. The Zygomatic gland, when identified, is situated near the eye, within the orbit, close to the zygomatic arch, but in the pig, this area is occupied by the dorsal buccal glands.
Significance of Salivary Gland Location in Health Assessment
Understanding the location of porcine salivary glands is useful for veterinary health monitoring and diagnosis. The superficial placement of the parotid and mandibular glands allows for physical examination through palpation. Veterinarians and producers can feel for changes in size, texture, or temperature in these regions.
Swelling of a salivary gland (sialadenitis) or the presence of tumors and cysts becomes noticeable due to the fixed anatomical coordinates of the tissue. Knowing the location helps differentiate a swollen gland from nearby enlarged lymph nodes. Collecting saliva is a noninvasive method for detecting diseases, stress hormones, and biomarkers. Changes in gland health impact the composition and volume of saliva, making the system an indicator of overall physiological status.