Topic overview

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Saliva begins digestion and protects oral tissues; it contains bicarbonate and potassium, digestive enzymes, and antimicrobial components, with secretion under parasympathetic control. Gastric juice includes hydrochloric acid, pepsinogen, intrinsic factor, and mucus. Acid secretion is shaped by stimulatory signals—gastrin, histamine, and acetylcholine—and inhibitory signals such as somatostatin, prostaglandins, and secretin. Pancreatic juice contributes digestive enzymes and bicarbonate, with secretin and CCK coordinating key components. Bile supports fat emulsification, while bile salts are recycled through enterohepatic circulation. The topic also introduces alkaline mucus from Brunner’s glands and clinical associations involving excess gastrin, intrinsic-factor deficiency, VIPoma, and pancreatic insufficiency.