Chapter 43: Pancreatic and Salivary Glands

The pancreas serves dual roles as both an endocrine gland producing hormones like insulin and glucagon, and an exocrine gland generating digestive enzymes and bicarbonate-rich fluid. The chapter details pancreatic acinar cells and their synthesis of inactive enzyme precursors called zymogens, which undergo activation in the small intestine to digest proteins, carbohydrates, and lipids. Ductal cells contribute bicarbonate secretion regulated by secretin, which neutralizes stomach acid and creates an optimal pH for intestinal enzyme function. The chapter explores the neural and hormonal control mechanisms governing pancreatic secretion, including the roles of the vagus nerve, cholecystokinin, and secretin in coordinating digestive responses to food intake. Salivary glands, including the parotid, submandibular, and sublingual glands, produce saliva containing enzymes like amylase and lipase alongside mucus, water, and electrolytes. Salivary secretion involves both sympathetic and parasympathetic innervation, with parasympathetic stimulation generally producing copious watery secretions and sympathetic activity yielding more viscous, mucus-rich output. The chapter addresses the composition of primary and secondary saliva, ion transport mechanisms in ductal modification, and the protective functions of saliva including lubrication, antimicrobial defense, and buffering capacity. Clinical considerations such as salivary dysfunction, xerostomia, and pancreatic insufficiency are discussed in relation to their metabolic and nutritional consequences. Understanding these glandular systems is fundamental to appreciating how the body coordinates digestion and maintains oral homeostasis.